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2022, Vol. 68, No. 5　Online: 15 May 2022

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Reversible faradaic reactions involving redox mediators and oxygen-containing groups on carbon fiber electrode for high-performance flexible fibrous supercapacitors SoobeomLee, Geon-HyoungAn 2022, 68(5): 1-11.  DOI: 10.1016/j.jechem.2021.11.008 Abstract ( 23 )   PDF (15301KB) ( 3 )   Flexible fibrous supercapacitors (FFS) are taking account of as the energy storage devices for wearable electronics owing to their high power density, high safety, long cycle life, and simple manufacturing process. Nevertheless, FFSs have the disadvantage of low specific capacitance that results from the electrochemical characteristics of the electrical double layer on the carbon fiber electrode. In this study, for the first time, an FFS comprising surface-activated carbon fibers as an electrode/current collector and a redox additive gel polymer electrolyte (FFS-SARE) was fabricated for use as a wearable energy storage device. The FFS-SARE showed outstanding electrochemical performance, namely, high specific capacitances of 891 and 399 mF cm-2 at current densities of 70.0 and 400 μA cm-2, respectively, and remarkable ultrafast cycling stability over 5000 cycles with 92% capacitance retention at a current density of 400.0 μA cm-2. Moreover, they exhibited mechanical flexibility and had high feasibility, and they showed good energy storage performance that renders them suitable for use in wearable electronic textiles.

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Improved crystallinity and self-healing effects in perovskite solar cells via functional incorporation of polyvinylpyrrolidone Yunjuan Niu, Dingchao He, Zhengguo Zhang, Jun Zhu, Tulloch Gavin, Polycarpos Falaras, Linhua Hu 2022, 68(5): 12-18.  DOI: 10.1016/j.jechem.2021.10.029 Abstract ( 17 )   PDF (3996KB) ( 10 )   Air moisture is the key issue for perovskites which invades the films and accelerates the damage of devices. Here, polyvinylpyrrolidone (PVP) is introduced to the methylammonium lead iodide (MAPbI3) perovskite precursor to control crystal growth and endow the devices with self-healing ability in a moisture environment. The strong CΟ⋯ΗΝ hydrogen bonding interactions between PVP and MAPbI3was confirmed by nuclear magnetic resonance measurements. By introducing hydrogen bonding in the MAPbI3-based PSCs, we form a compact perovskite film of excellent electronic quality with a power conversion efficiency (PCE) of up to 20.32%. Furthermore, the Ο⋯ΗΝ hydrogen bonding interactions at the grain boundaries suppress the decomposition of methylammonium cations and improve the recyclable dissolution-recrystallization of perovskite. As a result, the MAPbI3-PVP based cells exhibited striking moisture stability and self-healing behavior, with negligible decay in efficiency after 500 h of operation in high humidity (65% ± 5% relative humidity) and rapid recovering ability after their removal from the humid environment.

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Highly controlled structured catalysts for on-board methanol reforming Zhuangdian Liang, Gang Wang, Gaofeng Zeng, Jie Zhang, Zhiyong Tang 2022, 68(5): 19-26.  DOI: 10.1016/j.jechem.2021.11.030 Abstract ( 8 )   PDF (5938KB) ( 3 )   The on-board methanol steam reforming (MSR) has long been considered as an effective approach to in-situ produce hydrogen for fuel cell vehicles (FCVs). However, the conventional MSR catalyst pellets suffer from easy breakage during the vehicle movement, leading to increased pressure drop and reduced system stability. Herein, we introduce an integrated method to prepare the highly controlled structured catalysts based on coupled processes: direct prototyping the structured substrate using digital light processing (DLP) 3D printing technology, in-situ dynamic crystallization of active components assisted by magnetic resonance imaging (MRI) and calcination. The synthesized catalyst owns a gradient layer of active component, and exhibits better MSR performance, higher mechanical strength, reduced pressure drop, higher Cu dispersion and better adhesion of active compounds when compared with the conventional powder and pellet catalysts. The demonstrated successful application proves the feasibility of developed method, which has great potential to be used for preparing precisely other monolithic catalysts with customized structures.

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Enhanced interfacial compatibility of FeS@N,S-C anode with ester-based electrolyte enables stable sodium-ion full cells Jiyu Zhang, Zhen Meng, Dan Yang, Keming Song, Liwei Mi, Yunpu Zhai, Xinxin Guan, Weihua Chen 2022, 68(5): 27-34.  DOI: 10.1016/j.jechem.2021.11.033 Abstract ( 12 )   PDF (8322KB) ( 8 )   The development of sodium-ion full cells is seriously suppressed by the incompatibility between electrodes and electrolytes. Most representatively, high-voltage ester-based electrolytes required by the cathodes present poor interfacial compatibility with the anodes due to unstable solid electrode interphase (SEI). Herein, FeS@N,S-C (spindle-like FeS nanoparticles individually encapsulated in N,S-doped carbon) with excellent structural stability is synthesized as a potential sodium anode material. It exhibits exceptional interfacial stability in ester-based electrolyte (1 M NaClO4 in ethylene carbonate/propylene carbonate with 5% fluoroethylene carbonate) with long-cycling lifespan (294 days) in Na|FeS@N,S-C coin cell and remarkable cyclability in pouch cell (capacity retention of 82.2% after 170 cycles at 0.2 A g-1). DFT calculation reveals that N,S-doping on electrode surface could drive strong repulsion to solvated Na+ and preferential adsorption to ClO4-anion, guiding the anion-rich inner Helmholtz plane. Consequently, a robust SEI with rich inorganic species (NaCl and Na2O) through the whole depth stabilizes the electrode-electrolyte interface and protects its integrity. This work brings new insight into the role of electrode’s surface properties in interfacial compatibility that can guide the design of more versatile electrodes for advanced rechargeable metal-ion batteries.

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Small molecule interfacial cross-linker for highly efficient two-dimensional perovskite solar cells Hongming Hou, Taotao Hu, Fu Zhang, Rui Liu, Jialong He, Chang Liu, Yue Yu, Dong Chen, Qiaofeng Wu, Meng Zhang, Hua Yu 2022, 68(5): 35-41.  DOI: 10.1016/j.jechem.2021.10.026 Abstract ( 13 )   PDF (3686KB) ( 3 )   The nonradiative recombination of charge carriers at the hole transport layer (HTL)/perovskite interface generally induces remarkable performance loss of the inverted two-dimensional perovskite solar cells (2D PSCs). Herein, a cross-linkable small molecule of 2-mercaptoimidazole (2-MI) was introduced into the nickel oxide (NiOx)/2D perovskite interface. Experiments have confirmed the formation of Ni-N covalent bond by N atom in the 2-MI and Ni in the NiOx and the coordinating between S atom of 2-MI and under-coordinated Pb2+ near to the NiOx/perovskite interface, which contributes to creating a cross-linking between NiOx/perovskite interface to restrain charge carrier recombination and enhance the extraction of hole carriers at the interface. Besides, the 2-MI modification layer is also beneficial for promoting the crystallinity of 2D perovskite. Consequently, the inverted 2D PSCs with 2-MI modification achieved the best power conversion efficiency of 15%. This paves a route to acquire highly efficient 2D PSCs by constructing a cross-linking at the NiOx HTL/2D perovskite interface.

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Non-layer-transformed Mn3O4 cathode unlocks optimal aqueous magnesium-ion storage via synergizing amorphous ion channels and grain refinement Zhongyu Pan, Tingting Qin, Wei Zhang, Xianyu Chu, Taowen Dong, Nailin Yue, Zizhun Wang, Weitao Zheng 2022, 68(5): 42-48.  DOI: 10.1016/j.jechem.2021.11.031 Abstract ( 4 )   PDF (6202KB) ( 6 )   Aqueous rechargeable magnesium ion batteries (ARMBs) have obtained more attention due to the two-electrons transfer nature, low cost and safety. However, the scarcity of cathode materials seriously hinders the development of ARMBs because of the unfavorable strong interaction between Mg2+ and cathode material. Herein, we choose a pre-treated spinel Mn3O4 cathode for aqueous Mg2+ storage. The pre-treatment in Na2SO4 solution induces the grain refinement decorated with tortuous amorphous ion diffusion channels, facilitating the production of electrochemical reaction active sites and the diffusion of Mg2+, respectively, which achieve a (sub-)surface pseudocapacitance reaction between Mn (II) and Mn (III). As a result, the pre-treated Mn3O4 cathode exhibits a package of optimal performances, i.e., a capacity of 98.9 mAh g-1 and a high capacity retention rate of 99.4% after 2000 cycles. To the best of our knowledge, our work not only provides a new reaction mechanism of spinel Mn3O4 in aqueous batteries system, but also affords a high cycle stability electrode material for rechargeable Mg2+ energy storage.

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Boosting solar water oxidation activity of BiVO4photoanode through an efficient in-situ selective surface cation exchange strategy Kai Song, Fang He, Ergang Zhou, Lin Wang, Huilin Hou, Weiyou Yang 2022, 68(5): 49-59.  DOI: 10.1016/j.jechem.2021.11.024 Abstract ( 9 )   PDF (9549KB) ( 3 )   The sluggish kinetics for water oxidation is recognized as one of the major problems for the unsatisfied photoelectrochemical (PEC) performance. Herein, we developed a feasible strategy based on in-situ selective surface cation exchange, for activating surface water oxidation reactivity toward boosted PEC water oxidation of BiVO4 photoanodes with fundamentally improved surface charge transfer. The as-constructed Co/BiVO4 photoanodes exhibit 2.6 times increase in photocurrent density with superior stability, in comparison to those of pristine counterpart. Moreover, the faradaic efficiency of as-fabricated photoanode can be up to ∼ 95% at 1.23 V (vs. RHE). The unique selective replacement of Bi by Co on the surface could modify the electronic structure of BiVO4 with reduced energy barrier of the deprotonation of OH* to O, thus favoring the overall excellent PEC performance of Co/BiVO4 photoanode.

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Unraveling transition-metal-mediated stability of spinel oxide via in situ neutron scattering Yan Chen, Ke An 2022, 68(5): 60-70.  DOI: 10.1016/j.jechem.2021.10.024 Abstract ( 6 )   PDF (11857KB) ( 2 )   The energy materials performance is intrinsically determined by structures from the average lattice structure to the atom arrangement, valence, and distribution of the containing transition metal (TM) elements. Understanding the mechanism of the structure transition and atom rearrangement via synthesis or processing is key to expediting the exploration of excellent energy materials. In this work, in situneutron scattering is employed to reveal the real-time structure evolution, including the TM-O bonds, lattice, TM valence and the migration of the high-voltage spinel cathode LiNi0.5Mn1.5O4. The transition-metal-mediated spinel destabilization under the annealing at the oxygen-deficient atmosphere is pinpointed. The formation of Mn3+ is correlated to the TM migration activation, TM disordered rearrangement in the spinel, and the transition to a layered-rocksalt phase. The further TM interdiffusion and Mn2+ reduction are also revealed with multi-stage thermodynamics and kinetics. The mechanisms of phase transition and atom migrations as functions of temperature, time and atmosphere present important guidance on the synthesis in various-valence element containing oxides.

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Phase control and stabilization of 1T-MoS2 via black TiO2-x nanotube arrays supporting for electrocatalytic hydrogen evolution Ting Zhang, Tingxuan Yang, Guoxing Qu, Saifang Huang, Peng Cao, Wei Gao 2022, 68(5): 71-77.  DOI: 10.1016/j.jechem.2021.10.031 Abstract ( 5 )   PDF (4828KB) ( 2 )   1T phase MoS2 (1T-MoS2) is a promising substitute of platinum electrocatalyst for hydrogen evolution reaction (HER) due to its high intrinsic activity but suffering from thermodynamical instability. Although great efforts have been made to synthesize 1T-MoS2 and enhance its stability, it remains a big challenge to realize the phase control and stabilization of 1T-MoS2. Herein, based on crystal field theory analysis, we propose a new solution by designing an electrocatalyst of 1T-MoS2nanosheets anchoring on black TiO2-x nanotube arrays in-situ grown on Ti plate (1T-MoS2/TiO2-x@Ti). The black TiO2-x substrate is expected to play as electron donors to increase the charge in Mo 4d orbits of 1T-MoS2 and thus weaken the asymmetric occupation of electrons in the Mo 4d orbits. Experimental results demonstrate that black TiO2-x nanotubes shift electrons to MoS2 and induce MoS2to generate more 1T phase due to stabilizing the 1T-MoS2 nanosheets compared with a Ti substrate. Thus 1T-MoS2/TiO2-x@Ti shows much improved HER performance with a small Tafel slope of 42 mV dec-1 and excellent catalytic stability with negligible degradation for 24 h. Theoretical calculations confirm that the black TiO2-x substrate can effectively stabilize metastable 1T-MoS2 due to electrons transferring from black TiO2-x to Mo 4d orbits. This work sheds light on the instability of 1T-MoS2 and provides an essential method to stabilize and efficiently utilize 1T-MoS2 for HER.

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Coordination and interface engineering to boost catalytic property of two-dimensional ZIFs for wearable Zn-air batteries Hang Lei, Shangjing Yang, Qixiang Wan, Liang Ma, Muhammad Sufyan Javed, Shaozao Tan, Zilong Wang, Wenjie Mai 2022, 68(5): 78-86.  DOI: 10.1016/j.jechem.2021.11.013 Abstract ( 4 )   PDF (9132KB) ( 2 )   Metal organic frameworks (MOFs) have been considered as compelling precursor for miscellaneous applications. However, their unsatisfied electrocatalytic performance limits their direct application as electrocatalyst. Herein, by incorporating the cobalt-oxide bonds and polyaniline (PANI) with two-dimension zeolitic imidazolate frameworks (ZIFs), a novel bifunctional catalyst (Co-O-ZIF/PANI) for Zn-air battery was designed based on a facile and eco-friendly method. This Co-O-ZIF/PANI with optimized surface adsorption effect and suitable Co3+/Co2+ ratio, exhibits eminent electrocatalytic activity toward both oxygen reduction and evolution reaction. The as-assembled liquid ZABs based on Co-O-ZIF/PANI achieves a remarkable maximum power density of 123.1 mW cm-2 and low discharge-charge voltage gap of 0.81 V at 5 mA cm-2 for over 300 cycles. Operando Raman spectroscopy reveals that the excellent performance origins from the optimized surface chemisorption property of O2 and H2O brought by Co-O bonds and PANI. This work provides a novel prospect to develop efficient MOF derived bifunctional electrocatalysts by optimizing surface chemisorption properties.

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Self-assembled donor-acceptor hole contacts for inverted perovskite solar cells with an efficiency approaching 22%: The impact of anchoring groups Qiaogan Liao, Yang Wang, Zilong Zhang, Kun Yang, Yongqiang Shi, Kui Feng, Bolin Li, Jiachen Huang, Peng Gao, Xugang Guo 2022, 68(5): 87-95.  DOI: 10.1016/j.jechem.2021.11.001 Abstract ( 7 )   PDF (3774KB) ( 3 )   Self-assembled molecules (SAMs) have shown great potential in replacing bulk charge selective contact layers in high-performance perovskite solar cells (PSCs) due to their low material consumption and simple processing. Herein, we design and synthesize a series of donor-acceptor (D-A) type SAMs (MPA-BT-CA, MPA-BT-BA, and MPA-BT-RA, where MPA is 4-methoxy-N-(4-methoxyphenyl)-N-phenylaniline; BT is benzo[c][1,2,5]-thiadiazole; CA is 2-cyanoacrylic acid, BA is benzoic acid, RA is rhodanine-3-propionic acid) with distinct anchoring groups, which show dramatically different properties. MPA-BT-CA with CA anchoring groups exhibited stronger dipole moments and formed a homogeneous monolayer on the indium tin oxide (ITO) surface by adopting an upstanding self-assembling mode. However, the MPA-BT-RA molecules tend to aggregate severely in solid state due to the sp3hybridization of the carbon atom on the RA group, which is not favorable for achieving a long-range ordered self-assembled layer. Consequently, benefiting from high dipole moment, as well as dense and uniform self-assembled film, the device based on MPA-BT-CA yielded a remarkable power conversion efficiency (PCE) of 21.81%. Encouragingly, an impressive PCE approaching 20% can still be obtained for the MPA-BT-CA-based PSCs as the device area is increased to 0.80 cm2. Our work sheds light on the design principles for developing hole selecting SAMs, which will pave a way for realizing highly efficient, flexible, and large-area PSCs.

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Controlled high-density interface engineering of Fe3O4-FeS nanoarray for efficient hydrogen evolution Min Yang, Wen-Hui Hu, Meng-Xuan Li, Yu-Ning Cao, Bin Dong, Yu Ma, Hui-Ying Zhao, Feng-Ge Wang, Jier Huang, Yong-Ming Chai 2022, 68(5): 96-103.  DOI: 10.1016/j.jechem.2021.11.032 Abstract ( 5 )   PDF (8354KB) ( 4 )   The rational design of double active sites system is vital for constructing high-efficiency iron sulfides electrocatalysts towards hydrogen evolution reaction (HER) in alkaline media. However, it remains a challenge to controllably create the high-density interface of double sites for optimal synergistic effect. Herein, we reported a simple chemical oxidation-induced surface reconfiguration strategy to obtain the interface-rich Fe3O4-FeS nanoarray supported on iron foam (Fe3O4-FeS/IF) using FeS nanosheets as precursors. The abundant Fe3O4-FeS interfaces could improve the dispersion of active sites and facilitate the electron transfer, leading to enhanced hydrogen evolution efficiency. And meanwhile, by altering the oxidation temperature, the content of S and O could be effectively controlled, further achieving the ratio optimization of Fe3O4 to FeS. Synchrotron-based X-ray absorption near-edge structure, X-ray photoelectron spectroscopy and ultraviolet photoemission spectroscopy consistently confirm the changes of electronic structure and d-band center of Fe3O4-FeS after chemical oxidation. Consequently, Fe3O4-FeS/IF exhibits excellent alkaline HER activity with a low overpotential of 120.8 mV to reach 20 mA cm-2, and remains stable ranging from 10, 20 to 50 mA cm-2 for each 20 h, respectively. Therefore, the facile and controllable chemical oxidation may be an effective strategy for designing high-density interfaces of transition metal-based sulfides towards alkaline HER.

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Nitrogen and fluorine co-doped TiO2/carbon microspheres for advanced anodes in sodium-ion batteries: High volumetric capacity, superior power density and large areal capacity Dan Lv, Dongdong Wang, Nana Wang, Hongxia Liu, Shaojie Zhang, Yansong Zhu, Kepeng Song, Jian Yang, Yitai Qian 2022, 68(5): 104-112.  DOI: 10.1016/j.jechem.2021.11.040 Abstract ( 13 )   PDF (9049KB) ( 19 )   Fast charging and high volumetric capacity are two of the critical demands for sodium-ion batteries (SIBs). Although nanostructured materials achieve outstanding rate performance, they suffer from low tap density and small volumetric capacity. Therefore, how to realize large volumetric capacity and high tap density simultaneously is very challenging. Here, N/F co-doped TiO2/carbon microspheres (NF-TiO2/C) are synthesized to achieve both of them. Theoretical calculations reveal that N and F co-doping increases the contents of oxygen vacancies and narrows the bandgaps of TiO2 and C, improving the electronic conductivity of NF-TiO2/C. Furthermore, NF-TiO2/C exhibits the high binding energy and low diffusion energy barrier of Na+, significantly facilitating Na+ storage and Na+ diffusion. Therefore, NF-TiO2/C offers a high tap density (1.51 g cm-3), an outstanding rate performance (∼125.9 mAh g-1 at 100 C), a large volumetric capacity (∼190 mAh cm-3 at 100 C), a high areal capacity (∼4.8 mAh cm-2) and an ultra-long cycling performance (∼80.2% after 10,000 cycles at 10 C) simultaneously. In addition, NF-TiO2/C||Na3V2(PO4)3 full cells achieve an ultrahigh power density of 25.2 kW kg-1. These results indicate the great promise of NF-TiO2/C as a high-volumetric-capacity and high-power-density anode material of SIBs.

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Engineering core-shell Co9S8/Co nanoparticles on reduced graphene oxide: Efficient bifunctional Mott-Schottky electrocatalysts in neutral rechargeable Zn-Air batteries Xingkun Wang, Guangming Zhan, Yurou Wang, Yan Zhang, Jian Zhou, Ren Xu, Huiyu Gai, Huanlei Wang, Heqing Jiang, Minghua Huang 2022, 68(5): 113-123.  DOI: 10.1016/j.jechem.2021.09.014 Abstract ( 7 )   PDF (6801KB) ( 2 )   It is significant for the rational construction of the high-efficient bifunctional electrocatalysts for in-depth understandings of how to improve the electron transfer and ion/oxygen transport in catalyzing oxygen reduction reaction and oxygen evolution reaction (ORR and OER), but still full of vital challenges. Herein, we synthesize the novel “three-in-one” catalyst that engineers core-shell Mott-Schottky Co9S8/Co heterostructure on the defective reduced graphene oxide (Co9S8/Co-rGO). The Co9S8/Co-rGO catalyst exhibits abundant Mott-Schottky heterogeneous-interfaces, the well-defined core-shell nanostructure as well as the defective carbon architecture, which provide the multiple guarantees for enhancing the electron transfer and ion/oxygen transport, thus boosting the catalytic ORR and OER activities in neutral electrolyte. As expected, the integrated core-shell Mott-Schottky Co9S8/Co-rGO catalyst delivers the most robust and efficient rechargeable ZABs performance in neutral solution electrolytes accompanied with a power density of 59.5 mW cm-2 and superior cycling stability at 5 mA cm-2 over 200 h. This work not only emphasizes the rational designing of the high-efficient bifunctional oxygen catalysts from the fundamental understanding of accelerating the electron transfer and ion/oxygen transport, but also sheds light on the practical application prospects in more friendly environmentally neutral rechargeable ZABs.

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Utilizing bimetallic catalysts to mitigate coke formation in dry reforming of methane Jaylin Sasson Bitters, Tina He, Elizabeth Nestler, Sanjaya D. Senanayake, Jingguang G.Chen, Cheng Zhang 2022, 68(5): 124-142.  DOI: 10.1016/j.jechem.2021.11.041 Abstract ( 8 )   PDF (9611KB) ( 3 )   Dry reforming of methane (DRM) involves the conversion of carbon dioxide (CO2) and methane (CH4) into syngas (a mixture of hydrogen, H2, and carbon monoxide, CO), which can then be used to produce a wide range of products by means of Fischer-Tropsch synthesis. DRM has gained much attention as a means of mitigating damage from anthropogenic greenhouse gas (GHGs) emissions to the environment and instead utilizing these gases as precursors for value-added chemicals or to synthesize sustainable fuels and chemicals. Carbon deposition or coke formation, a primary cause of catalyst deactivation, has proven to be a major challenge in the development of DRM catalysts. The use of nickel- and cobalt-based catalysts has been extensively explored for DRM for their high activity and low cost but suffer from poor stability due to coke formation that has hindered their commercialization. Numerous articles have reviewed the various aspects of catalyst deactivation and strategies for mitigation, but few has focused on the benefit of bimetallic catalysts for mitigating coke formation. Bimetallic catalysts, often improve the catalytic stability over their monometallic counterparts due to synergistic effects resulting from two metal-to-metal interactions. This review will cover DRM literature for various bimetallic catalyst systems, including the effect of supports and promoters, on the mitigation of carbonaceous deactivation.

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Doped graphene/carbon black hybrid catalyst giving enhanced oxygen reduction reaction activity with high resistance to corrosion in proton exchange membrane fuel cells Zhaoqi Ji, Jianuo Chen, María Pérez-Page, Zunmin Guo, Ziyu Zhao, Rongsheng Cai, Maxwell T.P. Rigby, Sarah J. Haigh, Stuart M. Holmes 2022, 68(5): 143-153.  DOI: 10.1016/j.jechem.2021.09.031 Abstract ( 7 )   PDF (8805KB) ( 5 )   Nitrogen doping of the carbon is an important method to improve the performance and durability of catalysts for proton exchange membrane fuel cells by platinum-nitrogen and carbon-nitrogen bonds. This study shows that p-phenyl groups and graphitic N acting bridges linking platinum and the graphene/carbon black (the ratio graphene/carbon black = 2/3) hybrid support materials achieved the average size of platinum nanoparticles with (4.88 ± 1.79) nm. It improved the performance of the lower-temperature hydrogen fuel cell up to 0.934 W cm-2 at 0.60 V, which is 1.55 times greater than that of commercial Pt/C. Doping also enhanced the interaction between Pt and the support materials, and the resistance to corrosion, thus improving the durability of the low-temperature hydrogen fuel cell with a much lower decay of 10 mV at 0.80 A cm-2 after 30 k cycles of an in-situ accelerated stress test of catalyst degradation than that of 92 mV in Pt/C, which achieves the target of Department of Energy (<30 mV). Meanwhile, Pt/NrEGO2-CB3 remains 78% of initial power density at 1.5 A cm-2 after 5 k cycles of in-situ accelerated stress test of carbon corrosion, which is more stable than the power density of commercial Pt/C, keeping only 54% after accelerated stress test.

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Review on engineering two-dimensional nanomaterials for promoting efficiency and stability of perovskite solar cells Qingwei Zhou, Jialong Duan, Yanyan Duan, Qunwei Tang 2022, 68(5): 154-175.  DOI: 10.1016/j.jechem.2021.09.017 Abstract ( 9 )   PDF (23543KB) ( 6 )   Perovskite solar cell (PSC) has gradually shown its great superiority in photovoltaic filed to compete commercial solar cells owing to its great advantages, such as high efficiency and low fabrication cost. On the way towards commercialization, great efforts have been achieved by accelerating charge extraction and reducing carrier recombination. Recently, two-dimensional (2D) layered materials have attracted increasing interests for application in PSCs due to their distinctive chemical and physical properties, such as high carrier mobility and tunable bandgap, which greatly determines the perovskite film growth kinetics, carrier transfer and stability of PSCs. Therefore, with the aim to better understand their recent development and application in PSC, in this review, the emerging 2D materials beyond graphene as charge transport layers, buffer layers and additives in perovskite film for enhancing the efficiency and stability of PSCs are summarized. However, there are still some crucial challenges to be addressed for commercialization. Finally, the challenges and prospects of these 2D nanomaterials for application in PSCs are further proposed for future development.

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Improving the stability and scalability of all-inorganic inverted CsPbI2Br perovskite solar cell Chenghao Duan, Qiaoyun Wen, Yan Fan, Jiong Li, Zidan Liu, Keyou Yan 2022, 68(5): 176-183.  DOI: 10.1016/j.jechem.2021.11.026 Abstract ( 5 )   PDF (7277KB) ( 2 )   All-inorganic perovskite solar cells (PSCs) have potential to pass the stability international standard of IEC61215:2016 but cannot deliver high performance and stability due to the poor interface contact. In this paper, Sn-doped TiO2 (Ti1-xSnxO2) ultrathin nanoparticles are prepared for electron transport layer (ETL) by solution process. The ultrathin Ti0.9Sn0.1O2 nanocrystals have greatly improved interface contact due to the facile film formation, good conductivity and high work function. The all-inorganic inverted NiOx/CsPbI2Br/Ti0.9Sn0.1O2 p-i-n device shows a power conversion efficiency (PCE) of 14.0%. We tested the heat stability, light stability and light-heat stability. After stored in 85 °C for 65 days, the inverted PSCs still retains 98% of initial efficiency. Under continuous standard one-sun illumination for 600 h, there is no efficiency decay, and under continuous illumination at 85 °C for 200 h, the device still retains 85% of initial efficiency. The 1.0 cm2 device of inverted structure shows a PCE of up to 11.2%. The ultrathin Ti1-xSnxO2 is promising to improve the scalability and stability and thus increase the commercial prospect.

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The ORR electron transfer kinetics control via Co-Nx and graphitic N sites in cobalt single atom catalysts in alkaline and acidic media Tong Shen, Xiaoxiao Huang, Shibo Xi, Wei Li, Shengnan Sun, Yanglong Hou 2022, 68(5): 184-194.  DOI: 10.1016/j.jechem.2021.10.027 Abstract ( 9 )   PDF (13863KB) ( 2 )   Cost-effective 3d transition metal (TM) based single atom catalysts (SACs) for oxygen reduction reaction (ORR) are potential alternatives for Pt-based electrocatalysts in fuel cells and metal-air batteries. Understanding the effects of SACs’ properties and active site composition on the catalytic performance is significant to construct highly efficient catalysts. Here, we successfully promote the activity of cobalt single atoms decorated on N-doped carbon nanosheets via tuning the content of different nitrogen components, which outperforms most reported cobalt SACs. The activity and kinetics show positive correlation trends with the content of Co-Nx and graphitic N, serving as the main active sites. Furthermore, ORR kinetics in alkaline media can be positively affected by the conductivity of catalysts while no similar relation is observed in acidic media. The slight loss of Co-Nx sites engenders a mild change of performance in alkaline media, while the decrease of Co-Nx site activity due to chemical oxidation of carbon support and the loss of Co-Nx sites in acidic media exacerbate the degradation of performance. Our work provides an insight into the relation between ORR electron transfer kinetics and active sites in 3d TM based SACs.

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Constructing nanocomposites with robust covalent connection between nanoparticles and polymer for high discharged energy density and excellent tensile properties Jiachen Ma, Yabin Zhang, Yan Zhang, Luqing Zhang, Shuxiang Zhang, Xuchuan Jiang, Hong Liu 2022, 68(5): 195-205.  DOI: 10.1016/j.jechem.2021.11.022 Abstract ( 7 )   PDF (8500KB) ( 2 )   High discharged energy density and excellent flexible properties in dielectric materials are significantly sought to meet the rapid advancements in the electronics industry. In this study, covalent bonds are constructed between poly(vinylidene fluoride-chlorotrifluoroethylene), which contains olefinic bonds, and thiol-modified BaTiO3 at the interface before the nanocomposite films are fabricated. The presence of the covalent bonds is proved to promote the dispersibility of the modified BaTiO3 and enhance the interfacial adhesion between the modified BaTiO3 and the polymer, followed by a remarkably positive effect in suppressing the dielectric loss (tanδ) and increasing the breakdown strength (Eb) of the nanocomposite films. In addition, the cross-linking treatment in the preparation process is found to be favourable for improving the mechanical properties of the nanocomposite films, which benefits the enhancement of Eb. Furthermore, at 400% elongation, the stretched nanocomposite film doped with 5 vol% modified BaTiO3exhibits an Eb 15.6% greater than that of the unstretched film, and the discharged energy density reaches 11.4 J/cm3 with a high discharge energy efficiency of 84.5%. This study provides a novel strategy for preparing flexible nanocomposites with powerful interfacial adhesion at high filler content to achieve high discharged energy density.

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Misfit strains inducing voltage decay in LiMnyFe1-yPO4/C Chun Luo, Yao Jiang, Xinxin Zhang, Chuying Ouyang, Xiaobin Niu, Liping Wang 2022, 68(5): 206-212.  DOI: 10.1016/j.jechem.2021.11.007 Abstract ( 11 )   PDF (13197KB) ( 11 )   LiMnyFe1-yPO4 is considered a promising cathode material for next-generation lithium-ion batteries (LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the capacity loss during cycling. However, in this study, we find that the energy density degradation mainly roots in voltage decay. We have synthesized a series of LiMnyFe1-yPO4/C (0.5 ≤ y ≤ 0.8) and find this voltage decay is correlated with the Mn content. A high amount Mn leads to a heavier voltage decay. In-situ X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) reveal the nature of this effect, which show a mismatch along the b-axis of -2.68% (charge) and +3.4% (discharge), a volume misfit of -4.41% (charge) and +4.54% (discharge) between LixMnyFe1-yPO4and MnyFe1-yPO4 during phase transitions. The resultant misfit strains during Li+insertion compared to extraction result in structural degradations, such as amorphization and impurity (MnF3) accumulation after cycling. The voltage decay can be alleviated by kinetic relaxations and recovered by a wild reannealing. This work demonstrates effective strategies to improve the energy density and cycling performance of LiMnyFe1-yPO4/C, providing good references for other LIB cathodes, such as the Li-rich cathodes.

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The regulation of coordination structure between cobalt and nitrogen on graphene for efficient bifunctional electrocatalysis in Zn-air batteries Xinxin Shu, Maomao Yang, Miaomiao Liu, Wei Pan, Jintao Zhang 2022, 68(5): 213-221.  DOI: 10.1016/j.jechem.2021.11.018 Abstract ( 6 )   PDF (9283KB) ( 2 )   Electrocatalysts with atomically dispersed metal moieties are of importance in enhancing electrocatalysis for a specific reaction including oxygen reduction. However, it is still challenging to modulate the coordination structure of metal atoms with heteroatoms on carbon supports. Herein, an innovative and facile bridging strategy to regulate the coordination structure of cobalt with nitrogen atoms on reduced graphene oxide (rGO) sheets was developed by the interfacial complexation of amino-rich folic acid with cobalt ions on graphene oxide sheets and the subsequent thermal treatment. Typically, the actual coordination interaction between cobalt and nitrogen species was revealed by using X-ray absorption spectroscopy (XAS), exhibiting the Co-N4 coordination structure well-dispersed on reduced graphene oxide. Such unique structure enables the efficient oxygen reduction and evolution reactions via the favorable adsorption and desorption of intermediates. With the enhanced bifunctional electrocatalytic activities, the fabricated Zn-air battery exhibited the excellent performance with large power density of 319.8 mW cm-2 and good long-term stability (over 300 h). This work establishes the synthesis strategy for bridging metal atom with heteroatom on graphene sheets to enhance the bifunctional electrocatalysis toward Zn-air batteries.

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Current status and trends of carbon-based electrodes for fully solution-processed perovskite solar cells Laura M. González, Daniel Ramirez, Franklin Jaramillo 2022, 68(5): 222-246.  DOI: 10.1016/j.jechem.2021.11.020 Abstract ( 13 )   PDF (33400KB) ( 7 )   Perovskite solar cells (PSCs) have revolutionized photovoltaic research. As a result, a certified power conversion efficiency (PCE) of 25.5% was recorded in late 2020. Although this efficiency is comparable with silicon solar cells; some issues remain partially unsolved, such as lead toxicity, instability of perovskite materials under continuous illumination, moisture and oxygen, and degradation of the metallic counter electrodes. As an alternative to tackle this last concern, carbon materials have been recently used, due to their good electrical and thermal conductivity, and chemical stability, which makes them one of the most promising materials to replace metallic counter electrodes in the fabrication of PSCs. This review highlights the recent advances of carbon-based PSCs, where the carbon electrode (CE) is the main actor. CEs have become very promising candidates for PSCs; they are mainly fabricated using a simple combination of graphite and carbon black powders embedded in a binder matrix, giving a paste that is then solution-processable, resulting in devices with improved quality stability, when compared to metallic electrodes. In this review, CE’s composition is emphasized, since it can give both, high and low-temperature processed electrodes, compatible with different device configurations. Finally, the tendencies and opportunities to use CE in PSCs devices are presented.

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Porous polybenzimidazole membranes with positive charges enable an excellent anti-fouling ability for vanadium-methylene blue flow battery Dongju Chen, Guangyu Liu, Jie Liu, Changkun Zhang, Zhizhang Yuan 2022, 68(5): 247-254.  DOI: 10.1016/j.jechem.2021.12.011 Abstract ( 4 )   PDF (2782KB) ( 2 )   A cost-effective, high-performance and highly stable membrane has always been in intensively needed in aqueous organic-based flow batteries. Here we present a porous polybenzimidazole (PBI) membrane with positive charges that endow the membrane with a high rejection and an excellent anti-fouling ability for target organic molecule and asymmetric structure that affords a high conductivity for vanadium-methylene blue flow battery (V-MB FB). The morphologies and thickness of separating layer in particular of the porous PBI can be well adjusted by simply altering the polymer concentration in the cast solution and further afford the membrane with a controllable property in terms of both ion selectivity and ion conductivity. As a result, a V-MB FB assembled with a porous PBI membrane delivers a coulombic efficiency (CE) of 99.45% and an energy efficiency (EE) of 86.10% at a current density of 40 mA cm-2, which is 12% higher than that afforded by a Nafion 212 membrane. Most importantly, the V-MB FB demonstrates a methylene blue (MB) utilization of 97.55% at a theoretical capacity of 32.16 Ah L-1(based on the concentration of MB in the electrolyte) because of the high ion conductivity of the membrane, which favors reducing the cost of a battery. The results suggest that the designed porous PBI membranes exhibit a very promising prospect for methylene blue-vanadium flow battery.

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A techno-economic and life cycle assessment for the production of green methanol from CO2: catalyst and process bottlenecks Tomas Cordero-Lanzac, Adrian Ramirez, Alberto Navajas, Lieven Gevers, Sirio Brunialti, Luis M. Gandía, Andrés T. Aguayo, S. Mani Sarathy, Jorge Gascon 2022, 68(5): 255-266.  DOI: 10.1016/j.jechem.2021.09.045 Abstract ( 9 )   PDF (6375KB) ( 6 )   The success of catalytic schemes for the large-scale valorization of CO2 does not only depend on the development of active, selective and stable catalytic materials but also on the overall process design. Here we present a multidisciplinary study (from catalyst to plant and techno-economic/lifecycle analysis) for the production of green methanol from renewable H2 and CO2. We combine an in-depth kinetic analysis of one of the most promising recently reported methanol-synthesis catalysts (InCo) with a thorough process simulation and techno-economic assessment. We then perform a life cycle assessment of the simulated process to gauge the real environmental impact of green methanol production from CO2. Our results indicate that up to 1.75 ton of CO2 can be abated per ton of produced methanol only if renewable energy is used to run the process, while the sensitivity analysis suggest that either rock-bottom H2 prices (1.5 $ kg-1) or severe CO2 taxation (300 $ per ton) are needed for a profitable methanol plant. Besides, we herein highlight and analyze some critical bottlenecks of the process. Especial attention has been paid to the contribution of H2 to the overall plant costs, CH4 trace formation, and purity and costs of raw gases. In addition to providing important information for policy makers and industrialists, directions for catalyst (and therefore process) improvements are outlined.

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Effect of alloying on the carrier dynamics in high-performance perovskite solar cells Jing Wang, Wan-Jian Yin 2022, 68(5): 267-274.  DOI: 10.1016/j.jechem.2021.11.016 Abstract ( 8 )   PDF (3774KB) ( 2 )   High-efficiency solar cells often require light absorbers prepared from alloys, such as CdTe1-xSex, CuInxGa1-xSe2, Cu2ZnSnS4-xSex, and (CsxFA1-x)Pb(I1-yBry)3. However, how alloying affects solar cell performance is poorly understood, and determining common features associated with alloying is of significant interest. Herein, we studied the correlation between the A/X site compositional ratio and the photo-generated carrier dynamics using mixed halide perovskites (CsxFA1-x)Pb(IyBr1-y)3 as examples. Nonadiabatic molecular dynamics calculations demonstrated that charge carrier recombination is highly sensitive to the compositional ratio at the A/X-site. The enhanced lifetime is attributable to the suppression of atomic fluctuations, the weakening of electron-phonon coupling, and a reduction in the electron-transition probability between band edges. The optimal Br concentration was determined to be ∼18%, in agreement with experimental observations. This study not only advances our understanding of why mixed perovskites usually exhibit superior experimental photoelectric properties, but also provides a route for optimizing the carrier lifetimes and efficiencies of perovskite solar cells.

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Unlocking the electrocatalytic activity of natural chalcopyrite using mechanochemistry Zhijie Chen, Renji Zheng, Wenfei Wei, Wei Wei, Bing-Jie Ni, Hong Chen 2022, 68(5): 275-283.  DOI: 10.1016/j.jechem.2021.11.005 Abstract ( 8 )   PDF (11627KB) ( 4 )   Manipulating the structure self-reconstruction of transition metal sulfide-based (pre)catalysts during the oxygen evolution reaction (OER) process is of great interest for developing cost-effective OER catalysts, which remains a central challenge. Here we realize a deep structure self-reconstruction of natural chalcopyrite to unlock its OER performance via mechanochemical activation. Compared with the manually milled counterpart (CuFeS2-HM), the mechanically milled catalyst (CuFeS2-BM) with a reduced crystallinity exhibits a 7.11 times higher OER activity at 1.53 V vs. RHE. In addition, the CuFeS2-BM requires a low overpotential of 243 mV for generating 10 mA cm-2 and exhibits good stability over 24 h. Further investigations suggest that the excellent OER performance of CuFeS2-BM mainly originates from the decreased crystallinity induced the in situ deep structure self-reconstruction of the originally sulfides into the electroactive and stable metal (oxy)hydroxide phase (e.g., α-FeOOH) via S etching under OER conditions. This study demonstrates that regulating the crystallinity of catalysts is a promising design strategy for developing highly efficient OER catalysts via managing the structure self-reconstruction process, which can be further extended to the design of efficient catalysts for other advanced energy conversion devices. In addition, this study unveils the great potentials of engineering abundant natural minerals as cost-effective catalysts for diverse applications.

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Facile synthesis of KVPO4F/reduced graphene oxide hybrid as a high-performance cathode material for potassium-ion batteries Jianzhi Xu, Jiaying Liao, Yifan Xu, Jianbo Li, Chuannan Zhu, Jun Lin, Xiaosi Zhou 2022, 68(5): 284-292.  DOI: 10.1016/j.jechem.2021.12.023 Abstract ( 6 )   PDF (6482KB) ( 3 )   Potassium-ion batteries (PIBs) as a substitute for lithium-ion batteries have aroused widespread attention and have been rapidly developed. In the positive electrode materials, polyanionic compound has a high working voltage and large reversible capacity on account of its distinct framework and the strong inducing effect of the anionic group. Herein, a KVPO4F/reduced graphene oxide (KVPF/rGO) hybrid was fabricated via a simple multi-step approach as the polyanionic cathode material for PIBs. Profiting from the small size of KVPF nanoparticles and their uniform distribution in the rGO framework, the as-synthesized KVPF/rGO hybrid manifests a large discharge capacity of 103.2 mAh g-1 with an outstanding energy density of 436.5 Wh kg-1. Through rGO decoration, the hybrid also demonstrates remarkable rate and cycling properties. By employing ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, the potassium storage mechanism of KVPF was clearly revealed. The facile preparation procedure and superior properties endow it great application prospects in large-scale energy storage.

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Simple hybrid dithiafulvenes-triphenylamine systems as dopant-free hole-transporting materials for efficient perovskite solar cells Zhongquan Wan, Yunpeng Zhang, Jinyu Yang, Jianxing Xia, Fangyan Lin, Xiaojun Yao, Junsheng Luo, Chunyang Jia 2022, 68(5): 293-299.  DOI: 10.1016/j.jechem.2021.11.039 Abstract ( 9 )   PDF (2760KB) ( 12 )   Two extended hybrid conjugated systems based on a triphenylamine (TPA) core with two and three peripheral 1,4-dithiafulvenes (DTF) units coded WH-2 and WH-3 as hole-transporting materials (HTMs) applied in perovskite solar cells (PSCs) are synthesized by facile one-step reaction in good yield over 75%. DTF unit as electron donor can enhance the electron donating ability and the fusion of benzenic ring of TPA with DTF unit may lead to reinforced intermolecular interactions in the solid state. In addition, WH-2 and WH-3 exhibit a pyramid shape containing partial planarity and quasi three-dimensionality features, which is also conducive to enhancing the π-π stacking of molecules in the solid state. The above-mentioned structural characteristics make the two HTMs have good hole mobilities. As a result, WH-2 and WH-3 obtained the high intrinsic hole mobilities of 4.69 × 10-4 and 2.18 × 10-3 cm2 V-1 s-1 respectively. Finally, the power conversion efficiencies (PCEs) of PSCs with WH-2 and WH-3 as cost-effective dopant-free HTMs are 15.39% and 19.22% respectively and the PCE of PSC with WH-3 is on a par with that of PSC with Li-TFSI/t-BP doped Spiro-OMeTAD (19.67%).

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High-valence sulfur-containing species in solid electrolyte interphase stabilizes lithium metal anodes in lithium-sulfur batteries Li-Peng Hou, Li-Yang Yao, Chen-Xi Bi, Jin Xie, Bo-Quan Li, Jia-Qi Huang, Xue-Qiang Zhang 2022, 68(5): 300-305.  DOI: 10.1016/j.jechem.2021.12.024 Abstract ( 9 )   PDF (3664KB) ( 4 )   The interfacial stability of lithium metal anodes dictated by solid electrolyte interphase (SEI) is essential for long-cycling high-energy-density lithium-sulfur batteries. Nevertheless, critical components of SEI for interfacial stabilization are particularly indistinct. Herein, the effect of various sulfur-containing components in SEI for stabilizing lithium metal anodes is disclosed in lithium-sulfur batteries. High-valence sulfur-containing species (Li2SO3 and Li2SO4) in SEI are conducive to uniform lithium deposition and stabilizing lithium metal anodes. In contrast, low-valence sulfur-containing species (Li2S and Li2S2) in SEI result in aggressive lithium dendrites and dead lithium. This work identifies the role of sulfur-containing components in SEI for stabilizing lithium metal anodes and provides rational design principles of SEI for protecting lithium metal anodes in practical lithium-sulfur batteries.

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Interlayer environment engineered MXene: Pre-intercalated Zn2+ ions as intercalants renders the modulated Li storage Yixuan Wang, Miao Liu, Zhihe Wang, Qinhua Gu, Bo Liu, Cuimei Zhao, Junkai Zhang, Shichong Xu, Ming Lu, Haibo Li, Bingsen Zhang 2022, 68(5): 306-313.  DOI: 10.1016/j.jechem.2021.11.019 Abstract ( 6 )   PDF (5173KB) ( 2 )   The intercalation of foreign species into MXene, as an approach of tuning the interlayer environment, is employed to improve electrochemical ion storage behaviors. Herein, to understand the effect of confined ions by the MXene layers on the performance of electrochemical energy storage, Zn2+ ions were employed to intercalate into MXene via an electrochemical technique. Zn2+ ions induced a shrink of the adjacent MXene layers. Meaningfully, a higher capacity of lithium ion storage was obtained after Zn2+ pre-intercalation. In order to explore the roles of the intercalated Zn2+ ions, the structural evolution, and the electronic migration among Zn, Ti and the surface termination were investigated to trace the origination of the higher Li+ storage capacity. The pre-intercalated Zn2+ ions lost electrons, meanwhile Ti of MXene obtained electrons. Moreover, a low-F surface functional groups was achieved. Contrary to the first shrink, after 200 cycles, a larger interlayer distance was monitored, this can accelerate the ion transport and offer a larger expansile space for lithium storage. This may offer a guidance to understand the roles of the confined ion by two-dimensional (2D) layered materials.

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Dual-shell silicate and alumina coating for long lasting and high capacity lithium ion batteries Marcos Lucero, Tucker M. Holstun, Yudong Yao, Ryan Faase, Maoyu Wang, Alpha T. N'Diaye, David P. Cann, Joe Baio, Junjing Deng, Zhenxing Feng 2022, 68(5): 314-323.  DOI: 10.1016/j.jechem.2021.11.014 Abstract ( 4 )   PDF (7304KB) ( 2 )   Here we demonstrate a theory-driven, novel dual-shell coating system of Li2SrSiO4and Al2O3, achieved via a facile and scalable sol-gel technique on LiCoO2 electrode particles. The optimal thickness of each coating can lead to increased specific capacity (∼185 mAh/g at 0.5C-rate) at a cut-off potential of 4.5 V, and greater cycling stability at very high C rates (up to 10C) in half-cells with lithium metal. The mechanism of this superior performance was investigated using a combination of X-ray and electron characterization methods. It shows that the results of this investigation can inform future studies to identify still better dual-shell coating schemes, achieved by such industrially feasible techniques, for application on similar, nickel-rich cathode materials.

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The effect of temperature on ionic liquid modified Fe-N-C catalysts for alkaline oxygen reduction reaction Thomas Wolker, Kai Brunnengräber, Ioanna Martinaiou, Nick Lorenz, Gui-Rong Zhang, Ulrike I. Kramm, Bastian J.M. Etzold 2022, 68(5): 324-329.  DOI: 10.1016/j.jechem.2021.11.042 Abstract ( 7 )   PDF (2253KB) ( 4 )   Modifying solid catalysts with an ionic liquid layer is an effective approach for boosting the performance of both Pt-based and non-precious metal catalysts toward the oxygen reduction reaction. While most studies operated at room temperature it remains unclear whether the IL-associated boosting effect can be maintained at elevated temperature, which is of high relevance for practical applications in low temperature fuel cells. Herein, Fe-N-C catalysts were modified by introducing small amounts of hydrophobic ionic liquid, resulting in boosted electrocatalytic activity towards the alkaline oxygen reduction reaction at room temperature. It is demonstrated that the boosting effect can be maintained and even strengthened when increasing the electrolyte temperature up to 70 °C. These findings show for the first time that the incorporation of ionic liquid is a suited method to obtain advanced noble metal-free electrocatalysts that can be applied at operating temperature condition.

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Review of current progress in hole-transporting materials for perovskite solar cells Prerna Mahajan, Bhavya Padha, Sonali Verma, Vinay Gupta, Ram Datt, Wing Chung Tsoi, Soumitra Satapathi, Sandeep Arya 2022, 68(5): 330-386.  DOI: 10.1016/j.jechem.2021.12.003 Abstract ( 7 )   PDF (20477KB) ( 3 )   Recent advancements in perovskites' application as a solar energy harvester have been astonishing. The power conversion efficiency (PCE) of perovskite solar cells (PSCs) is currently reaching parity (>25 percent), an accomplishment attained over past decades. PSCs are seen as perovskites sandwiched between an electron transporting material (ETM) and a hole transporting material (HTM). As a primary component of PSCs, HTM has been shown to have a considerable effect on solar energy harvesting, carrier extraction and transport, crystallization of perovskite, stability, and price. In PSCs, it is still necessary to use a HTM. While perovskites are capable of conducting holes, they are present in trace amounts, necessitating the use of an HTM layer for efficient charge extraction. In this review, we provide an understanding of the significant forms of HTM accessible (inorganic, polymeric and small molecule-based HTMs), to motivate further research and development of such materials. The identification of additional criteria suggests a significant challenge to high stability and affordability in PSC.

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Synergistic stabilization of CsPbI3 inorganic perovskite via 1D capping and secondary growth Jingya Mi, Yuetian Chen, Xiaomin Liu, Xingtao Wang, Yanfeng Miao, Yabing Qi, Yixin Zhao 2022, 68(5): 387-392.  DOI: 10.1016/j.jechem.2021.12.019 Abstract ( 2 )   PDF (2739KB) ( 2 )   Cesium lead iodide (CsPbI3) perovskite has gained great attention in the photovoltaic (PV) community because of its unique optoelectronic properties, good chemical stability and appropriate bandgap for sunlight harvesting applications. However, compared to solar cells fabricated from organic-inorganic hybrid perovskites, the commercialization of devices based on all-inorganic CsPbI3perovskites still faces many challenges regarding PV performance and long-term stability. In this work, we discovered that tetrabutylammonium bromide (TBABr) post-treatment to CsPbI3 perovskite films could achieve synergistic stabilization with both TBA+ cation intercalation and Br-doping. Such TBA+ cation intercalation leads to one-dimensional capping with TBAPbI3 perovskite formed in situ, while the Br-induced crystal secondary growth helps effectively passivate the defects of CsPbI3perovskite, thus enhancing the stability. In addition, the incorporation of TBABr can improve energy-level alignment and reduce interfacial charge recombination loss for better device performance. Finally, the highly stable TBABr-treated CsPbI3-based perovskite solar cells show reproducible photovoltaic performance with a champion efficiency up to 19.04%, while retaining 90% of the initial efficiency after 500 h storage without encapsulation.

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The role of solvents in the formation of methylammonium lead triiodide perovskite Junke Jiang, José Manuel Vicent-Luna, Shuxia Tao 2022, 68(5): 393-400.  DOI: 10.1016/j.jechem.2021.12.030 Abstract ( 4 )   PDF (2849KB) ( 3 )   Metal halide perovskites (MHPs) are gaining increasing attention as low-cost, high-performance semiconductors for optoelectronics. In particular, their solution processing is compatible with the large-scale manufacturing of thin-film devices, including solar cells and light-emitting diodes. Understanding the coordination chemistry in precursor-solvent solution and atomistic mechanisms of film formation is of great importance for optimizing the optoelectronic properties of the final films. Using the methylammonium lead triiodide (MAPbI3) as an example, we study the complex evolution of the molecular species from the solution to the initial stage of the crystallization by using a combination of density functional theory (DFT) calculations and ab-initio molecular dynamics (AIMD) simulations. We focus on the widely employed solvents DMSO and DMF, analyze the structures and energies of the iodoplumbate complexes in the form of simple complex of [PbImLn]2-m and polymeric iodoplumbates of ([PbImLn]2-m)x. Based on the calculated formation enthalpies, we propose reaction schemes of MAPbI3 formation in DMSO, DMF and DMF-DMSO binary solvent and explain the advantages of the binary solvent. We highlight the important role of NH…O hydrogen bonds in the formation of iodoplumbates monomers. Our calculations indicate unbalanced reaction energies at several elementary reaction steps in either DMF (formation of [PbI4Ln]2- being highly favourable) or DMSO (formation of [PbI5Ln]3- being retarded). Mixing a small amount of DMSO in DMF gives rise to a better balance in the energies and, therefore, potentially better equilibria in the overall crystallization process and better quality of the final perovskite films.

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Defect-rich Mg-Al MMOs supported TEPA with enhanced charge transfer for highly efficient and stable direct air capture Meng Zhao, Jiewen Xiao, Wanlin Gao, Qiang Wang 2022, 68(5): 401-410.  DOI: 10.1016/j.jechem.2021.12.031 Abstract ( 10 )   PDF (7285KB) ( 5 )   Due to the advantages of low energy consumption and high CO2 selectivity, the development of solid amine-based materials has been regarded as a hot research topic in the field of DAC for the past decades. The adsorption capacity and stability over multiple cycles have been the top priorities for evaluation of practical application value. Herein, we synthesized a novel DAC material by loading TEPA onto defect-rich Mg0.55Al-O MMOs with enhanced charge transfer effect. The optimal Mg0.55Al-O-TEPA67% demonstrates the highest CO2 uptake of (3.0 mmol g-1) and excellent regenerability, maintaining ∼90% of the initial adsorption amount after 80 adsorption/desorption cycles. The in situ DRIFTS experiments suggested the formation of bicarbonate species under wet conditions. DFT calculations indicated that the stronger bonding between Mg0.55Al-O support and solid amine was caused by the abundance of oxygen defects on MMOs confirmed by XPS and ESR, which favors the charge transfer between the support and amine, resulting in intense interaction and excellent regenerability. This work for the first time conducted comprehensive and systematic investigation on the stabilization mechanism for MMOs supported solid amine adsorbents with highest uptake and superior cyclic stability in depth, which is different from the most popular SiO2-support, thus providing facile strategy and comprehensive theoretical mechanism support for future research about DAC materials.

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Adjusting the local solvation structures and hydrogen bonding networks for stable aqueous batteries with reduced cost Canfu Zhang, Binbin Chen, Haoran Cai, Renzhi Huang, Yingchun Liu, Huilin Pan 2022, 68(5): 411-419.  DOI: 10.1016/j.jechem.2021.12.005 Abstract ( 9 )   PDF (10468KB) ( 4 )   Exploring low-cost and effective approaches to extend the potentials of aqueous electrolytes is highly desired. Herein, it is found that the activity of H2O in aqueous electrolytes could be intensively manipulated by introducing small urea and long-chain polyethylene glycol (PEG) molecules into LiTFSI-H2O electrolyte systems without super salt concentration. The urea and PEG molecules could exclude partial coordinated H2O out of the inner solvation shell of Li+ and reconstruct hydrogen-bonding network between H2O and PEG molecules outside the solvation sheaths with restricted H2O activity and extended electrochemical window. The bonding competitions in aqueous electrolytes and their correlation to the electrochemical performance of full cells are studied. When the occurrence probability of H2O around Li+ is lower than 40%, stable cycling of 3.1 V LiMn2O4-Li4Ti5O12 full cell is achieved, showing 73% capacity retention after 200 cycles at 1 C rate in optimal electrolytes. This work provides new avenues to understand the role of H2O and explore low-cost and effective approaches for the development of next-generation aqueous lithium-ion batteries.

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Defects and doping engineering towards high performance lead-free or lead-less perovskite solar cells Wenying Cao, Zhaosheng Hu, Zhenhua Lin, Xing Guo, Jie Su, Jingjing Chang, YueHao 2022, 68(5): 420-438.  DOI: 10.1016/j.jechem.2021.12.002 Abstract ( 15 )   PDF (17169KB) ( 5 )   Up to now, perovskite solar cells (PSCs) have reached a certified 25.5% efficiency. As a promising photoelectric material, the metal halide perovskite possesses many outstanding properties such as tunable bandgap, long diffusion length, high absorption coefficient and carrier mobility. In spite of these remarkable properties, defects are inevitable during the solution processing. Therefore, many efforts have been made to reduce defects in perovskite films and thus improve the performance of devices. Among them, substitution or doping engineering is one of the most studied methods. Meanwhile, due to the poor stability of the organic-inorganic hybrid perovskite and the toxicity of Pb-based perovskite materials, all inorganic perovskite and lead-less or lead-free perovskite have emerged as promising materials. Here, we focus on the defect engineering especially substitutions on different sites in an ABX3 structure. The particular attention is devoted towards lead-less or lead-free perovskites, and we discuss several common elements or groups used to partially replace Pb2+. It is noted that proper elemental doping at different sites is an important guarantee for obtaining high-performance lead-less or lead-free PSCs.

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Atomically dispersed catalysts for small molecule electrooxidation in direct liquid fuel cells Jinfa Chang, Guanzhi Wang, Wei Zhang, Yang Yang 2022, 68(5): 439-453.  DOI: 10.1016/j.jechem.2021.12.017 Abstract ( 6 )   PDF (8126KB) ( 4 )   Direct liquid fuel cells (DLFCs) have received increasing attention because of their high energy densities, instant recharging abilities, simple cell structure, and facile storage and transport. The main challenge for the commercialization of DLFCs is the high loading requirement of platinum group metals (PGMs) as catalysts. Atomically dispersed catalysts (ADCs) have been brought into recent focus for DLFCs due to their well-defined active sites, high selectivity, maximal atom-utilization, and anti-poisoning property. In this review, we summarized the structure-property relationship for unveiling the underlying mechanisms of ADCs for DLFCs. More specifically, different types of fuels used in DLFCs such as methanol, formic acid, and ethanol were discussed. At last, we highlighted current challenges, research directions, and future outlooks towards the practical application of DLFCs.

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In situ transmission electron microscopy and artificial intelligence enabled data analytics for energy materials Hongkui Zheng, Xiner Lu, Kai He 2022, 68(5): 454-493.  DOI: 10.1016/j.jechem.2021.12.001 Abstract ( 23 )   PDF (55365KB) ( 13 )   Energy materials are vital to energy conversion and storage devices that make renewable resources viable for electrification technologies. In situ transmission electron microscopy (TEM) is a powerful approach to characterize the dynamic evolution of material structure, morphology, and chemistry at the atomic scale in real time and in operando. In this review, recent advancements of in situ TEM techniques for studying energy materials, including catalysts, batteries, photovoltaics, and thermoelectrics, are systematically discussed and summarized. The topics include a broad range of material transformations that are in situstimulated by heating, biasing, lighting, electron-beam illuminating, and cryocooling under vacuum, liquid, or gas environments within TEM, as well as the mechanistic understanding of the associated solid-solid, solid-liquid, and solid-gas reactions elucidated by in situ TEM examination and operando measurements. Special focus is also put on the emerging progress of artificial intelligence enabled microscopy data analytics, including machine learning enhanced tools for retrieving useful information from massive TEM imaging, diffraction, and spectroscopy datasets, highlighting its merits and potential for automated in situ TEM experimentation and analysis. Finally, the pressing challenges and future perspectives on in situ TEM study for energy-related materials are discussed.

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Metal-organic frameworks derived transition metal phosphides for electrocatalytic water splitting Li-Ming Cao, Jia Zhang, Li-Wen Ding, Zi-Yi Du, Chun-Ting He 2022, 68(5): 494-520.  DOI: 10.1016/j.jechem.2021.12.006 Abstract ( 10 )   PDF (34723KB) ( 3 )   It is critical to synthesize high-efficiency electrocatalysts to boost the performance of water splitting to meet the requirements of industrial applications. Metal-organic frameworks (MOFs) can function as ideal molecular platforms for the design of highly reactive transition metal phosphides (TMPs), a kind of candidates for high-efficiently electrocatalytic water splitting. The intrinsic activity of the electrocatalysts can be greatly improved via modulating the electronic structure of the catalytic center through the MOF precursors/templates. Moreover, the carbon layer converted in-situ by the organic ligands can not only protect the TMPs from being degraded in the harsh electrochemical environments, but also avoid agglomeration of the catalysts, thereby promoting their activities and stabilities. Furthermore, heteroatom-containing ligands can incorporate N, S or P, etc. atoms into the carbon matrixes after conversion, regulating the coordination microenvironments of the active centers as well as their electronic structures. In this review, we first summarized the latest developments in MOF-derived TMPs by the unique advantages in metal, organic ligand, and morphology regulations for electrocatalytic water splitting. Secondly, we concluded the critical scientific issues currently facing for designing state-of-the-art TMP-based electrocatalysts. Finally, we presented an outlook on this research area, encompassing electrocatalyst construction, catalytic mechanism research, etc.

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Interpenetrating structure for efficient Sb2Se3nanorod array solar cells loaded with CuInSe2QDs sensitizer Cong Liu, Zhenxiao Pan, Kai Shen, Jianzha Zheng, Xiaoyang Liang, Hongbing Zhu, Fei Guo, Zhiqiang Li, Ruud E.I. Schropp, Yaohua Mai 2022, 68(5): 521-528.  DOI: 10.1016/j.jechem.2021.11.002 Abstract ( 3 )   PDF (7271KB) ( 2 )   The strong anisotropic electrical properties of one-dimensional (1D) nanostructure semiconductors, especially the anisotropic carrier transport, have a negative and significant influence on the performance of solar cells if the nanostructures have random orientation. Considering the advantages of nanorod solar cells in carrier transport, we have achieved growth of vertically aligned Sb2Se3 nanorod array with highly (hk1) orientation on CdS substrate, and constructed superstrate nanorod solar cells for the first time. The Sb2Se3 nanorod array solar cells exhibit the more efficient and long-range carrier transport in vertical direction. Furthermore, in order to suppress interface recombination, a CuInSe2 quantum dots (QDs) sensitizer has been applied to fill the volume between the nanorods completely, thus forming an interpenetrating nanocomposite structure. The CuInSe2 QDs can harvest additional light by absorption of visible light and contribute photocurrent. Meantime, the QDs function as a hole transport material and thus reduce the dependence of lateral transport. Consequently, the interpenetrating nanocomposite CuInSe2/Sb2Se3 solar cells display a power conversion efficiency of 7.54% with significant enhancements in the short-circuit current density and open-circuit voltage over pure Sb2Se3 nanorod cells. This is the highest efficiency for superstrate solar cells based on Sb2Se3 nanorod arrays.

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Intensive-visible-light-responsive ANbO2N (A = Sr, Ba) synthesized from layered perovskite A5Nb4O15for enhanced photoelectrochemical water splitting Sukanya Ramaraj, Jeongsuk Seo 2022, 68(5): 529-537.  DOI: 10.1016/j.jechem.2021.12.015 Abstract ( 5 )   PDF (3825KB) ( 2 )   Nb-based, perovskite-type oxynitrides ANb(O,N)3 (A = Sr, Ba) have been significantly attractive semiconductor materials for photoelectrochemical (PEC) water splitting due to their absorption abilities of intensive-visible-light. However, PEC activities of these perovskites are relatively low due to reduction of Nb species during nitridation leading to the generation of anion defects and impurity phases. Herein, we propose nitridation of A-rich, layered perovskite A5Nb4O15 as starting oxides for general synthesis of photoactive ANbO2N. These layered perovskite A5Nb4O15 were completely transformed to single phase perovskite-type ANbO2N by nitridation. Wavelength onsets of light absorption were observed at 700 nm for SrNbO2N and at 740 nm for BaNbO2N. According to X-ray photoelectron spectroscopy results, excess Lewis base A species significantly suppressed the generation of reduced species such as Nb4+ and Nb3+ during nitridation, although it led to an amorphous surface of the as-prepared oxynitride. Subsequent annealing in Ar largely enhanced surface crystallinity of ANbO2N. As a result, Co(OH)x/ANbO2N/FTO photoanodes, prepared by loading Co(OH)x electrocatalyst, showed high photocurrent density of 1.6 (A = Sr) and 2.4 mA cm-2 (A = Ba) at 1.23 VRHE under AM 1.5 G simulated sunlight. These results demonstrate that A-rich layered perovskite A5Nb4O15 are effective starting precursors for preparing low-defective ANbO2N, thus improving PEC water splitting activity.

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Defect-engineered Mn3O4/CNTs composites enhancing reaction kinetics for zinc-ions storage performance Xiuli Guo, Hao Sun, Chunguang Li, Siqi Zhang, Zhenhua Li, Xiangyan Hou, Xiaobo Chen, Jingyao Liu, Zhan Shi, Shouhua Feng 2022, 68(5): 538-547.  DOI: 10.1016/j.jechem.2021.12.033 Abstract ( 5 )   PDF (11607KB) ( 1 )   The designing of reasonable nanocomposite materials and proper introduction of defect engineering are of great significance for the improvement of the poor electronic conductivity and slow reaction kinetics of manganese-based compounds. Herein, we report manganese-deficient Mn3O4 nanoparticles which grow in-situ on highly conductive carbon nanotubes (CNTs) (denoted as DMOC) as an advanced cathode material for aqueous rechargeable zinc-ion batteries (RAZIBs). According to experimental and calculation results, the DMOC cathode integrates the advantages of enriched Mn defects and small particle size. These features not only enhance electronic conductivity but also create more active site and contribute to fast reaction kinetics. Moreover, the structure of DMOC is maintained during the charging and discharging process, thus benefiting for excellent cycle stability. As a result, the DMOC electrode delivers a high specific capacity of 420.6 mA h g-1 at 0.1 A g-1 and an excellent cycle life of 2800 cycles at 2.0 A g-1 with a high-capacity retention of 84.1%. In addition, the soft-packaged battery assembled with DMOC cathode exhibits long cycle life and high energy density of 146.3 Wh kg-1 at 1.0 A g-1. The results are beneficial for the development of Zn/Mn3O4 battery for practical energy storage.

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A generalizable, data-driven online approach to forecast capacity degradation trajectory of lithium batteries Xinyan Liu, Xue-Qiang Zhang, Xiang Chen, Gao-Long Zhu, Chong Yan, Jia-Qi Huang, Hong-Jie Peng 2022, 68(5): 548-555.  DOI: 10.1016/j.jechem.2021.12.004 Abstract ( 20 )   PDF (6093KB) ( 17 )   Estimating battery degradation is vital not only to monitor battery’s state-of-health but also to accelerate research on new battery chemistries. Herein, we present a data-driven approach to forecast the capacity fading trajectory of lab-assembled lithium batteries. Features with physical meanings in addition to predictive abilities are extracted from discharge voltage curves, enabling online prediction for a single cell with only its historical data. The robustness and generalizability allow for the demonstration on a compromised quality dataset consisting of batteries varying in battery architectures and cycling conditions, with superior accuracy for end of life and degradation trajectory prediction with average errors of 8.2% and 2.8%, respectively. Apart from the impressive prediction accuracy, the as-extracted features also provide physical insights, the incorporation of which into material design or battery operation conditions further enlightens the development of better batteries. We highlight the effectiveness of time-series-based techniques in forecasting battery cycling performance, as well as the huge potential of data-driven methods in unveiling hidden correlations in complicated energy chemistries such as lithium metal batteries.

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Ultrasmall AuPd nanoclusters on amine-functionalized carbon blacks as high-performance bi-functional catalysts for ethanol electrooxidation and formic acid dehydrogenation Yuhuan Cui, Ming Zhao, Yining Zou, Junyu Zhang, Jiuhui Han, Zhili Wang, Qing Jiang 2022, 68(5): 556-563.  DOI: 10.1016/j.jechem.2021.12.029 Abstract ( 5 )   PDF (6286KB) ( 2 )   The synthesis of ultrasmall metal nanoclusters (NCs) with high catalytic activities is of great importance for the development of clean and renewable energy technologies but remains a challenge. Here we report a facile wet-chemical method to prepare ∼1.0 nm AuPd NCs supported on amine-functionalized carbon blacks. The AuPd NCs exhibit a specific activity of 5.98 mA cmAuPd-2 and mass activity of 5.25 A mgAuPd-1 for ethanol electrooxidation, which are far better than those of commercial Pd/C catalysts (1.74 mA cmPd-2 and 0.54 A mgPd-1). For formic acid dehydrogenation, the AuPd NCs have an initial turn over frequency of 49339 h-1 at 298 K without any additive, which is much higher than those obtained for most of reported AuPd catalysts. The reported synthesis may represent a facile and low-cost approach to prepare other ultrasmall metal NCs with high catalytic activities for various applications.

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Tailoring interphase structure to enable high-rate, durable sodium-ion battery cathode Na Li, Shaofei Wang, Enyue Zhao, Wen Yin, Zhigang Zhang, Kang Wu, Juping Xu, Yoshihiro Kuroiwa, Zhongbo Hu, Fangwei Wang, Jinkui Zhao, Xiaoling Xiao 2022, 68(5): 564-571.  DOI: 10.1016/j.jechem.2021.12.018 Abstract ( 13 )   PDF (4970KB) ( 10 )   Na-based layered transition metal oxides with O3-type structure have been considered to be promising cathodes for Na-ion batteries. However, the intrinsically limited Na-ion conductivity induced by the O-type Na-coordinate environment compromises their rate and cycle capability, hindering their practical application. Here, we report an interphase-structure tailoring strategy that improves the electrochemical properties of O3-type layered cathodes achieved through surface coating and doping processes. Specifically, a Zr-doped interphase structure is designed in the model compound NaNi1/3Mn1/3Fe1/3O2 using the ionic conductor Na3Zr2Si2PO12 as the surface coating material and Zr-dopant provider. We discover that the modified NaNi1/3Mn1/3Fe1/3O2 cathode shows a stable Na-storage structure as well as an enhanced rate/cycle capability. Combined with theoretical calculations, it is suggested that the superior electrochemical performances originate from the Zr-doped interphase structure, which has an enlarged Na layer spacing that forms favorable Na-ion diffusion channels. This work highlights a general material interface optimization method which opens a new perspective for fabricating high-performance electrodes for Na-ion batteries and beyond.

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Is proton a charge carrier for δ-MnO2 cathode in aqueous rechargeable magnesium-ion batteries? Zhenzhen Liu, Xiang Li, Jian He, Qian Wang, Ding Zhu, Yigang Yan, Yungui Chen 2022, 68(5): 572-579.  DOI: 10.1016/j.jechem.2021.12.016 Abstract ( 5 )   PDF (4191KB) ( 4 )   Manganese dioxide (MnO2) is considered as a potential cathode material for aqueous magnesium-ion batteries. However, the charge/discharge mechanism of MnO2 in aqueous electrolyte is still unclear. In present study, highly porous δ-MnO2 is investigated, which delivers a high capacity of 252.1 mAh g-1 at 0.05 A g-1and excellent rate capability, i.e., 109.7 mAh g-1 at 1 A g-1, but a low-capacity retention of 54.4% after 800 cycles at 1 A g-1. The two-step discharging process, namely a consequent H+ and Mg2+ insertion reaction, is verified, by comparing the electrochemical performance of δ-MnO2 in 1 M MgCl2 and 1 M MnCl2 aqueous electrolyte and analyzing detailedly the Mg content and the bonding state of Mn at different charge/discharge state. Furthermore, partial irreversibility of Mg2+ ion insertion/extraction is observed, which may be one of the major reasons leading to capacity decay.

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Specializing liquid electrolytes and carbon-based materials in EDLCs for low-temperature applications Pui-yan Hung, Huihui Zhang, Han Lin, Qiaoshi Guo, Kin-tak Lau, Baohua Jia 2022, 68(5): 580-602.  DOI: 10.1016/j.jechem.2021.12.012 Abstract ( 4 )   PDF (11524KB) ( 2 )   Electric double-layer capacitors (EDLCs) are emerging technologies to meet the ever-increasing demand for sustainable energy storage devices and systems in the 21st Century owing to their advantages such as long lifetime, fast charging speed and environmentally-friendly nature, which play a critical part in satisfying the demand of electronic devices and systems. Although it is generally accepted that EDLCs are suitable for working at low temperatures down to -40 °C, there is a lack of comprehensive review to summarize the quantified performance of EDLCs when they are subjected to low-temperature environments. The rapid and growing demand for high-performance EDLCs for auxiliary power systems in the aeronautic and aerospace industries has triggered the urge to extend their operating temperature range, especially at temperatures below -40 °C. This article presents an overview of EDLC’s performance and their challenges at extremely low temperatures including the capability of storing a considerable amount of electrical energy and maintaining long-term stability. The selection of electrolytes and electrode materials is crucial to the performance of EDLCs operating at a desired low-temperature range. Strategies to improve EDLC’s performance at extremely low temperatures are discussed, followed by the future perspectives to motivate more future studies to be conducted in this area.

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A flexible, robust, and high ion-conducting solid electrolyte membranes enabled by interpenetrated network structure for all-solid-state lithium metal battery Zhenchuan Tian, Dukjoon Kim 2022, 68(5): 603-611.  DOI: 10.1016/j.jechem.2021.12.035 Abstract ( 3 )   PDF (7574KB) ( 3 )   Poly(vinyl alcohol)/poly(ethylene glycol) (PVA/PEG) semi-interpenetrating networks (s-IPN) were synthesized for the application of solid electrolyte membranes of lithium metal batteries. Thermal, mechanical and dimensional stability, lithium-ion conductivity, interfacial compatibility, and cell performance were evaluated to assure their application. As this s-IPN structure suppressed the crystallinity by formation of network structure, both the lithium-ion conductivity and mechanical strength were simultaneously enhanced. The PVA/PEG-3s-IPN showed the highest lithium-ion conductivity of 3.26 × 10-4 S cm-1 in a wide electrochemical window (5.8 V vs. Li/Li+), maintaining the robust solid-state with the tensile strength beyond 16.2 MPa at room temperature. The synthesized solid electrolyte membranes exhibited quite high specific capacity over 122 mAh g-1 at 0.1 C from Li|PVA/PEG-3 s-IPN|LiFePO4 cell and the long-term stable lithium stripping/plating performance for 1000 cycles from Li symmetric cell.

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Work function tuned, surface Cs intercalated BiVO4 for enhanced photoelectrochemical water splitting reactions Shankara S. Kalanur, Hyungtak Seo 2022, 68(5): 612-623.  DOI: 10.1016/j.jechem.2021.12.039 Abstract ( 5 )   PDF (14864KB) ( 3 )   Monoclinic BiVO4 is a widely researched semiconductor in solar water splitting owing to its suitable characteristics. However, BiVO4 faces limitations, such as the inefficient separation and transportation of photogenerated charges in the bulk and poor catalytic water oxidation reactions at the surface that affect the water-splitting efficiency. In this work, the Cs intercalation strategy at the surface of BiVO4 is proposed for the enhanced water splitting to H2 and O2 productions via the effective separation and transportation photogenerated charges and improved surface catalytic water oxidation reactions. The Cs ions are found to intercalate at the surface of BiVO4 and regulate the oxygen vacancies to provide active O2production sites and stability. The surface intercalation of Cs boosts the photocurrent to 1.89 mA cm-2 at 1.23 V vs. reference hydrogen electrode (RHE). A stoichiometric evolution of H2 and O2 is recorded with a faradaic efficiency of 92%. The open-circuit voltage measurements confirmed the increase in the carrier lifetime with the work function tuning upon Cs intercalation. The proposed Cs intercalation strategy suggests an effective route to suppress the charge recombination with an increase in carrier lifetime and charge separation in BiVO4for the enhanced PEC application.

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Three-dimensional ordered hierarchically porous carbon materials for high performance Li-Se battery Hongyan Li, Wenda Dong, Chao Li, Tarek Barakat, Minghui Sun, Yingying Wang, Liang Wu, Lang Wang, Lei Xia, Zhi-Yi Hu, Yu Li, Bao-Lian Su 2022, 68(5): 624-636.  DOI: 10.1016/j.jechem.2021.12.036 Abstract ( 8 )   PDF (15736KB) ( 3 )   Developing host materials with high specific surface area, good electron conductivity, and fast ion transportation channel is critical for high performance lithium-selenium (Li-Se) batteries. Herein, a series of three dimensional ordered hierarchically porous carbon (3D OHPC) materials with micro/meso/macropores are designed and synthesized for Li-Se battery. The porous structure is tuned by following the concept of the generalized Murray's law to facilitate the mass diffusion and reduce ion transport resistance. The optimized 3D Se/OHPC cathode exhibits a very high 2nd discharge capacity of 651 mAh/g and retains 361 mAh/g after 200 cycles at 0.2 C. Even at a high current rate of 5 C, the battery still shows a discharge capacity as high as 155 mAh/g. The improved electrochemical performance is attributed to the synergy effect of the interconnected and well-designed micro, meso and macroporosity while shortened ions diffusion pathways of such Murray materials accelerate its ionic and electronic conductivities leading to the enhanced electrochemical reaction. The diffusivity coefficient in Se/OHPC can reach a very high value of 1.3 × 10-11 cm2/s, much higher than those in single pore size carbon hosts. Their effective volume expansion accommodation capability and reduced dissolution of polyselenides ensure the high stability of the battery. This work, for the first time, established the clear relationship between textural properties of cathode materials and their performance and demonstrates that the concept of the generalized Murray’s law can be used as efficient guidance for the rational design and synthesis of advanced hierarchically porous materials and the great potential of 3D OHPC materials as a practical high performance cathode material for Li-Se batteries.

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Organic-inorganic hybrid hole transport layers with SnS doping boost the performance of perovskite solar cells Xiaolu Zheng, Haibing Wang, Feihong Ye, Cong Chen, Weijun Ke, Wenjing Zhang, Chuanxin He, Yanlong Tai, Guojia Fang 2022, 68(5): 637-645.  DOI: 10.1016/j.jechem.2021.11.034 Abstract ( 5 )   PDF (10446KB) ( 1 )   Perovskite solar cells (PSCs) have demonstrated excellent photovoltaic performance which currently rival the long-standing silicon solar cells’ efficiency. However, the relatively poor device operational stability of PSCs still limits their future commercialization. Binary sulfide is a category of materials with promising optoelectrical properties, which shows the potential to improve both the efficiency and stability of PSCs. Here we demonstrate that the inorganic tin monosulfide (SnS) can be an efficient dopant in 2,2′,7,7′-tetrakis(N,N-di-p-methoxy-phenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) to form a composite hole transport layer (HTL) for PSCs. SnS nanoparticles (NPs) synthesized through a simple chemical precipitation method exhibit good crystallization and suitable band matching with the perovskites. The introduction of SnS NPs in Spiro-OMTAD HTLs enhanced charge extraction, reduced trap state density, and shallowed trap state energy level of the devices based on the composite HTLs. Therefore, the resulting solar cells employing SnS-doped spiro-OMeTAD HTLs delivered an improved stabilized power output efficiency of 21.75% as well as enhanced long-term stability and operational stability. Our results provide a simple method to modify the conventional spiro-OMeTAD and obtain PSCs with both high efficiency and good stability.

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Ultrafine VN nanodots induced generation of abundant cobalt single-atom active sites on nitrogen-doped carbon nanotube for efficient hydrogen evolution Yan Cheng, Juhui Gong, Bo Cao, Xuan Xu, Peng Jing, Shien-Ping Feng, Rui Cheng, Baocang Liu, Rui Gao, Jun Zhang 2022, 68(5): 646-657.  DOI: 10.1016/j.jechem.2021.11.035 Abstract ( 4 )   PDF (9613KB) ( 2 )   Development of highly active and stable non-noble electrocatalysts with well-defined nanostructures is crucial for efficient hydrogen evolution reaction (HER). Herein, a novel three-dimensional (3D) self-supported electrode consists of vanadium nitride (VN) nanodots and Co nanoparticles co-embedded and highly active single Co atoms anchored in N-doped carbon nanotubes supported on carbon cloth (VN-Co@CoSAs-NCNTs/CC) is fabricated via a one-step in situ nanoconfined pyrolysis strategy, which shows remarkable enhanced HER electrocatalytic activity in acidic medium. During pyrolysis, the formed VN nanodots induce the generation of atomic CoNx sites in NCNTs, contributing to superior electrocatalytic activity. Experimental and density functional theory (DFT) calculation results reveal that the electrode has multiple accessible active sites, fast reaction kinetics, low charge/mass transfer resistances, high conductivity, as well as downshifted d-band center with a thermodynamically favorable hydrogen adsorption free energy (ΔGH*), all of which greatly boost the HER performance. As a result, the VN-Co@CoSAs-NCNTs/CC electrode displays superb catalytic performance toward HER with a low overpotential of 29 mV at 10 mA cm-2 in acidic medium, which could maintain for at least 60 h of stable performance. This work opens a facile avenue to explore low-cost, high performance, but inexpensive metals/nitrogen-doped carbon composite electrocatalysts for HER.

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Amorphous phosphorus chalcogenide as an anode material for lithium-ion batteries with high capacity and long cycle life Jiale Yu, Haiyan Zhang, Yingxi Lin, Junyao Shen, Yiwen Xie, Xifeng Huang, Qiong Cai, Haitao Huang 2022, 68(5): 658-668.  DOI: 10.1016/j.jechem.2021.11.028 Abstract ( 4 )   PDF (20209KB) ( 2 )   The ever-increasing demands for modern energy storage applications drive the search for novel anode materials of lithium (Li)-ion batteries (LIBs) with high storage capacity and long cycle life, to outperform the conventional LIBs anode materials. Hence, we report amorphous ternary phosphorus chalcogenide (a-P4SSe2) as an anode material with high performance for LIBs. Synthesized via the mechanochemistry method, the a-P4SSe2 compound is endowed with amorphous feature and offers excellent cycling stability (over 1500 mA h g-1 capacity after 425 cycles at 0.3 A g-1), owing to the advantages of isotropic nature and synergistic effect of multielement forming Li-ion conductors during battery operation. Furthermore, as confirmed by ex situ X-ray diffraction (XRD) and transmission electron microscope (TEM), the a-P4SSe2 anode material has a reversible and multistage Li-storage mechanism, which is extremely beneficial to long cycle life for batteries. Moreover, the autogenous intermediate electrochemical products with fast ionic conductivity can facilitate Li-ion diffusion effectively. Thus, the a-P4SSe2 electrode delivers excellent rate capability (730 mA h g-1 capacity at 3 A g-1). Through in situ electrochemical impedance spectra (EIS) measurements, it can be revealed that the resistances of charge transfer (Rct) and solid electrolyte interphase (RSEI) decrease along with the formation of Li-ion conductors whilst the ohmic resistance (RΩ) remains unchanged during the whole electrochemical process, thus resulting in rapid reaction kinetics and stable electrode to obtain excellent rate performance and cycling ability for LIBs. Moreover, the formation mechanism and electrochemical superiority of the a-P4SSe2 phase, and its expansion to P4S3-xSex (x = 0, 1, 2, 3) family can prove its significance for LIBs.

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Electrocatalytic production of glycolic acid via oxalic acid reduction on titania debris supported on a TiO2 nanotube array Francesco Pio Abramo, Federica De Luca, Rosalba Passalacqua, Gabriele Centi, Gianfranco Giorgianni, Siglinda Perathoner, Salvatore Abate 2022, 68(5): 669-678.  DOI: 10.1016/j.jechem.2021.12.034 Abstract ( 6 )   PDF (1863KB) ( 4 )   Electrodes prepared by anodic oxidation of Ti foils are robust and not toxic materials for the electrocatalytic reduction of oxalic acid to glycolic acid, allowing the development of a renewable energy-driven process for producing an alcoholic compound from an organic acid at low potential and room temperature. Coupled with the electrochemical synthesis of the oxalic acid from CO2, this process represents a new green and low-carbon path to produce added value chemicals from CO2. Various electrodes prepared by anodic oxidation of Ti foils were investigated. They were characterized by the presence of a TiO2 nanotube array together with the presence of small patches, debris, or TiO2 nanoparticles. The concentration of oxygen vacancies, the amount of Ti3+ measured by X-ray photoelectron spectroscopy (XPS) and the intensity of the anodic peak measured by cyclic voltammetry, were positively correlated with the achieved oxalic acid conversion and glycolic acid yield. The analysis of the results indicates the presence of small amorphous TiO2nanoparticles (or surface patches or debris) interacting with TiO2 nanotubes, the sites responsible for the conversion of oxalic acid and glycolic acid yield. By varying this structural characteristic of the electrodes, it is possible to tune the glycolic acid to glyoxylic acid relative ratio. A best cumulative Faradaic efficiency (FE) of about 84% with FE to glycolic acid around 60% and oxalic conversion about 30% was observed.

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Co3O4/Mn3O4 hybrid catalysts with heterointerfaces as bifunctional catalysts for Zn-air batteries Qikai Huang, Xiongwei Zhong, Qi Zhang, Xin Wu, Miaolun Jiao, Biao Chen, Jinzhi Sheng, Guangmin Zhou 2022, 68(5): 679-687.  DOI: 10.1016/j.jechem.2021.12.032 Abstract ( 5 )   PDF (9522KB) ( 2 )   Zinc-air batteries (ZABs) with high energy density and safety are promising as next-generation energy storage systems, while their applications are severely hindered by the sluggish reaction kinetic of air cathodes. Developing a bifunctional catalyst with high activity and durability is an effective strategy to address the above challenges. Herein, a Co3O4/Mn3O4 nanohybrid with heterointerfaces is designed as advanced cathode catalyst for ZABs. Density functional theory calculations show the heterogeneous interface between Co3O4/Mn3O4 can improve the dynamics of carrier transport and thus enhancing the catalytic activity and durability. The Co3O4/Mn3O4 catalyst anchored on reduced graphene oxide (rGO) exhibits high oxygen reduction reaction (ORR) activity with a half-wave potential of 0.86 V, and excellent oxygen evolution reaction (OER) activity with the potential of 1.59 V at 10 mA cm-2, which are comparable to the commercial noble metal catalysts. The improved ORR/OER catalytic activity is ascribed to the synergistic effect of heterointerfaces between Co3O4 and Mn3O4 as well as the improved conductivity and contact area of oxygen/catalysts/electrolytes three-phase interface by rGO. Furthermore, a home-made ZAB based on Co3O4/Mn3O4/rGO shows a high open circuit voltage of 1.54 V, a large power density of 194.6 mW cm-2 and good long-term cycling stability of nearly 400 h at 5 mA cm-2, which affords a promising bifunctional oxygen catalyst for rechargeable ZABs.

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High sulfur-doped hard carbon anode from polystyrene with enhanced capacity and stability for potassium-ion storage Xiaoyan Chen, Xin-Bing Cheng, Zhigang Liu 2022, 68(5): 688-698.  DOI: 10.1016/j.jechem.2021.12.007 Abstract ( 10 )   PDF (6862KB) ( 7 )   Carbonaceous materials are regarded as a promising anode material for potassium ion batteries (PIBs) due to their high electronic conductivity, abundant resources and low cost. However, relatively low storage capacity and structural instability still hinder their practical application. Herein, high sulfur-doped hard carbon (SHC-3) with a sulfur up to 27.05 at% is synthesized from polystyrene and sulfur as precursors. As an anode for PIBs, the SHC-3 delivers a superb cycling stability and rate performance (298.1 mAh g-1 at 100 mA g-1 for 1000 cycles, a capacity retention of 95.2%; 220.2 mAh g-1 at 500 mA g-1 after 5200 cycles). The potassium storage of SHC-3 exhibits excellent cyclic stability at both low and high rates. Structure and kinetic studies demonstrate that the larger interlayer spacing (0.382 nm) of the SHC-3 accelerates the diffusion of potassium ions and effectively alleviates the volume expansion, and thus maintains the structure stability during the process of potassization/de-potassization. Meanwhile, the density functional theory calculation shows that the doped sulfur atoms provide abundant active sites for the adsorption of potassium ions, thereby increasing the reversible capacity of PIBs. This work provides a new scheme for the design of carbonaceous anode materials with high capacity and long cycle life.

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In-situ construction of N-doped carbon nanosnakes encapsulated FeCoSe nanoparticles as efficient bifunctional electrocatalyst for overall water splitting Yuan Pan, Minmin Wang, Min Li, Guangxun Sun, Yinjuan Chen, Yunqi Liu, Wei Zhu, Bin Wang 2022, 68(5): 699-708.  DOI: 10.1016/j.jechem.2021.12.008 Abstract ( 18 )   PDF (11027KB) ( 5 )   The development of bifunctional electrocatalysts with high activity and stability for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for efficient overall water splitting but still challenging. Herein, we propose a facile and effective polymerization-pyrolysis-selenization (PPS) strategy for in-situ synthesis of N-doped carbon nanosnakes (NCNSs) encapsulated Fe-doped CoSe nanoparticles (NPs) derived from predesigned trimetallic Zn/Fe/Co polyphthalocyanine conjugated polymer networks. Benefiting from the synergistic effect between the regulation of Fe atoms and CoSe NPs as well as the confinement effect of in situ formed porous conductive carbon nanosnakes, the FeCoSe@NCNSs catalyst exhibited the excellent electrocatalytic activity for HER with small overpotentials (142 and 99 mV in 0.5 M H2SO4 and 1 M KOH) and OER (320 mV in 1 M KOH) at the current density of 10 mA cm-2. Particularly, it also can be used as an efficient bifunctional electrocatalyst with a cell voltage of 1.66 V to achieve a current density of 10 mA cm-2 and superior stability for overall water splitting. Density functional theory study reveals that the doping of Fe atoms on CoSe enhanced the splitting and delocalization of metal-d orbitals close Fermi level, and modifies the distribution of Se-p orbitals close Fermi level, which improved the flexibility of electron donor-acceptor system and the hydrogen adsorption free energy change on metal-metal bridge sites in FeCoSe@NCNSs. Additionally, beneficial from the accepting of Fe-Se bridge site, the overpotential of OER which following intramolecular oxygen coupling mechanism is also decreased, thus accelerating the electrocatalytic performance. This work presents a novel strategy to regulate the activity and stability of transition metal selenides and facilitating the rational design of bifunctional electrocatalysts for overall water splitting applications.

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Driving the sodium-oxygen battery chemistry towards the efficient formation of discharge products: The importance of sodium superoxide quantification Marina Enterría, Marine Reynaud, Juan Ignacio Paredes, Lidia Medinilla, Reza Younesi, Nagore Ortiz-Vitoriano 2022, 68(5): 709-720.  DOI: 10.1016/j.jechem.2021.12.014 Abstract ( 2 )   PDF (5740KB) ( 4 )   Sodium-oxygen batteries (SOBs) have the potential to provide energy densities higher than the state-of-the-art Li-ion batteries. However, controlling the formation of sodium superoxide (NaO2) as the sole discharge product on the cathode side is crucial to achieve durable and efficient SOBs. In this work, the discharge efficiency of two graphene-based cathodes was evaluated and compared with that of a commercial gas diffusion layer. The discharge products formed at the surface of these cathodes in a glyme-based electrolyte were carefully studied using a range of characterization techniques. NaO2 was detected as the main discharge product regardless of the specific cathode material while small amounts of Na2O2⋅2H2O and carbonate-like side-products were detected by X-ray diffraction as well as by Raman and infrared spectroscopies. This work leverages the use of X-ray diffraction to determine the actual yield of NaO2 which is usually overlooked in this type of batteries. Thus, the proper quantification of the superoxide formed on the cathode surface is widely underestimated; even though is crucial for determining the efficiency of the battery while eliminating the parasitic chemistry in SOBs. Here, we develop an ex-situ analysis method to determine the amount of NaO2 generated upon discharge in SOBs by transmission X-ray diffraction and quantitative Rietveld analysis. This work unveils that the yield of NaO2 depends on the depth of discharge where high capacities lead to very low discharge efficiency, regardless of the used cathode. We anticipate that the methodology developed herein will provide a convenient diagnosis tool in future efforts to optimize the performance of the different cell components in SOBs.

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Noble-metal-based high-entropy-alloy nanoparticles for electrocatalysis Xianfeng Huang, Guangxing Yang, Shuang Li, Hongjuan Wang, Yonghai Cao, Feng Peng, HaoYu 2022, 68(5): 721-751.  DOI: 10.1016/j.jechem.2021.12.026 Abstract ( 25 )   PDF (18762KB) ( 23 )   Since the two seminal papers were published independently in 2004, high-entropy-alloys (HEAs) have been applied to structural and functional materials due to the enhanced mechanical properties, thermal stability, and electrical conductivity. In recent years, HEA nanoparticles (HEA-NPs) were paid much attention to in the field of catalysis for the promoted catalytic activity. Furthermore, the various ratios among the metal components and tunable bulk and surface structures enable HEAs have big room to enhance the catalytic performance. Especially, noble-metal-based HEAs displayed significantly improved performance in electrocatalysis, where the ‘core effects’ were employed to explain the superior catalytic activity. However, it is insufficient to understand the essential mechanism or further guide the design of electrocatalysts. Structure-property relationship should be disclosed for the catalysis on HEA-NPs to accelerate the process of seeking high effective and efficient electrocatalysts. Therefore, we summarized the recent advances of noble-metal-based HEA-NPs applied to electrocatalysis, such as hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, methanol oxidation reaction, ethanol oxidation reaction, formic acid oxidation reaction, hydrogen oxidation reaction, carbon dioxide reduction reaction and nitrogen reduction reaction. For each electrocatalytic reaction, the reaction mechanism and catalyst structure were presented, and then the structure-property relationship was elaborated. The review begins with the development, concept, four ‘core effect’ and synthesis methods of HEAs. Next, the electrocatalytic reactions on noble-metal-based HEA-NPs are summarized and discussed independently. Lastly, the main views and difficulties pertaining to structure-property relationship for HEAs are discussed.

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Fluorobenzene diluted low-density electrolyte for high-energy density and high-performance lithium-sulfur batteries Zhilong Han, Shuping Li, Mengjun Sun, Renjie He, Wei Zhong, Chuang Yu, Shijie Cheng, Jia Xie 2022, 68(5): 752-761.  DOI: 10.1016/j.jechem.2021.12.038 Abstract ( 5 )   PDF (12743KB) ( 3 )   The mass fraction of electrolytes is the crucial factor affecting the energy density of lithium-sulfur (Li-S) batteries. Due to the high porosity within the C/S cathode, high concentration of polysulfides, and side reaction in lithiun metal anode under lean electrolyte, it is extremely challenging to improve performance while reducing the electrolyte volume. Here, we report a novel electrolyte with relatively low density (1.16 g cm-3), low viscosity (1.84 mPa s), and high ionic conductivity, which significantly promotes energy density and cyclability of Li-S batteries under practical conditions. Moreover, such electrolyte enables a hybrid cathode electrolyte interphase (CEI) and solid electrolyte interface (SEI) layer with plentiful LiF, which leads to fast kinetics of ions transport and stable cyclability even under low temperatures. Compared to Li-S batteries in electrolyte employing 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) diluent, the ultra-thick cathode (20 mg cm-2) shows a high capacity of 9.48 mAh cm-2 and excellent capacity retention of 80.3% over 191 cycles at a low electrolyte-to-sulfur ratio (E/S = 2) and negative-to-positive capacity ratio (N/P = 2.5), realizing a 19.2% improvement in energy density in coin cells (from 370 to 441 Wh kg-1) and a high energy density up to 467 Wh kg-1 in pouch cells. This study not only provides guidance for the electrolyte design but also paves the way for the development of high performance Li-S batteries under practical conditions.

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The effect of NiO-Ni3N interfaces in in-situformed heterostructure ultrafine nanoparticles on enhanced polysulfide regulation in lithium-sulfur batteries Jun Pu, Zhenghua Wang, Pan Xue, Kaiping Zhu, Jiachen Li, Yagang Yao 2022, 68(5): 762-770.  DOI: 10.1016/j.jechem.2021.12.043 Abstract ( 6 )   PDF (13956KB) ( 1 )   Inhibiting the “shuttle effect” of soluble polysulfides and improving reaction kinetics are the key factors necessary for further exploration of high-performance Li-S batteries. Herein, an effective interface engineering strategy is reported, wherein nitriding of an Ni-based precursor is controlled to enhance Li-S cell regulation. The resulting in-situ formed NiO-Ni3N heterostructure interface not only has a stronger polysulfide adsorption effect than that of monomeric NiO or Ni3N but also has a faster Li ion diffusion ability than a simple physical mixture. More importantly, this approach couples the respective advantages of NiO and Ni3N to reduce polarization and facilitate electron transfer during polysulfide reactions and synergistically catalyze polysulfide conversion. In addition, ultrafine nanoparticles are thought to effectively improve the use of additive materials. In summary, Li-S batteries based on this NiO-Ni3N heterostructure have the features of long cycle stability, rapid charging-discharging, and good performance under high sulfur loading.

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CO2 hydrogenation to methanol promoted by Cu and metastable tetragonal CexZryOz interface Na Li, Weiwei Wang, Lixin Song, Hui Wang, Qiang Fu, Zhenping Qu 2022, 68(5): 771-779.  DOI: 10.1016/j.jechem.2021.12.053 Abstract ( 6 )   PDF (6939KB) ( 3 )   Designing effective catalyst to improve the activity of CO2 hydrogenation to methanol is a potential avenue to realize the utilization of CO2 resources. Herein we construct three kinds of Cu/CexZryOz (CCZ) catalysts with different crystal phases of CexZryOz solid solutions, which demonstrate distinct activity and methanol selectivity in the order of metastable tetragonal-CCZ (CCZ-t″, parts of oxygen in CexZryOz were replaced by tetragonal phase from cubic fluorite phase) > tetragonal-CCZ (CCZ-t) > cubic-CCZ (CCZ-c) for CO2 hydrogenation to methanol. Structural analysis reveals that oxygen vacancies, surface hydroxyls and unsaturated Cu species of CCZ all follow the same sequence as that of activity and methanol selectivity, indicating that the above features are beneficial to improve the catalytic reactionperformance. Temperature programmed experiments and mechanism studies show that the interface between Cu and tetragonal (t and t″) CexZryOz can promote CO2adsorption, and the adsorbed CO2 is more reactive and can generate active bidentate carbonate species, which can be hydrogenated to form active monodentate and bidentate formate species under CO2 and H2 atmosphere. These intermediates should be crucial to the formation of methanol product. CCZ-t″ has stronger H2activation ability than CCZ-t, which makes the former catalyst have more intermediates and higher methanol selectivity. In contrast, CO2 mainly adsorbs on cubic CexZryOz support of CCZ-c, but its H2 spillover ability is low, which hinders the reaction process. In addition, the strong adsorption of surface intermediates on CCZ-c is also not conducive to methanol formation. Results here demonstrate that constructing active Cu-support interfaces may be an important approach to design effective catalyst for CO2 hydrogenation.

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Controlled moderative sulfidation-fabricated hierarchical heterogeneous nickel sulfides-based electrocatalyst with tripartite Mo doping for efficient oxygen evolution Xing Yu, Qingyun Lv, Lulu She, Long Hou, Yves Fautrelle, Zhongming Ren, Guanghui Cao, Xionggang Lu, Xi Li 2022, 68(5): 780-788.  DOI: 10.1016/j.jechem.2021.12.010 Abstract ( 6 )   PDF (7357KB) ( 3 )   An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction (OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS2@Ni3S2/MoOx (NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm-2, small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec-1, which outperforms most reported sulfide catalysts and IrO2. The synergistic effects in the hierarchical heterostructures expose more active sites, adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.

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Chiral cation promoted interfacial charge extraction for efficient tin-based perovskite solar cells Weiyin Gao, He Dong, Nan Sun, Lingfeng Chao, Wei Hui, Qi Wei, Hai Li, Yingdong Xia, Xingyu Gao, Guichuan Xing, Zhongbin Wu, Lin Song, Peter Müller-Buschbaum, Chenxin Ran, Yonghua Chen 2022, 68(5): 789-796.  DOI: 10.1016/j.jechem.2021.09.019 Abstract ( 9 )   PDF (6310KB) ( 4 )   Pb-free Sn-based perovskite solar cells (PSCs) have recently made inspiring progress, and power conversion efficiency (PCE) of 14.8% has been achieved. However, due to the energy-level mismatch and poor interfacial contact between commonly used hole transport layer (i.e., poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS) and FASnI3 film, it is still challenging to effectively extract holes at the interface. Owing to the p-type nature of Sn-based perovskites, the efficient hole extraction is of particular significance to improve the PCE of their solar cells. In this work, for the first time, the role of chiral cations, α-methylbenzylamine (S-/R-/rac-MBA), in promoting hole transportation of FASnI3-based PSCs is demonstrated. The introduction of MBAs is found to form 2D/3D film with low-dimensional structures locating at PEDOT:PSS/FASnI3 interface, which facilitates the energy level alignment and efficient charge transfer at the interface. Importantly, chiral-induced spin selectivity (CISS) effect of R-MBA2SnI4 induced by chiral R-MBA cation is found to further assist the specific interfacial transport of accumulated holes. As a result, R-MBA-based PSCs achieve decent PCE of 10.73% with much suppressed hysteresis and enhanced device stability. This work opens up a new strategy to efficiently promote the interfacial extraction of accumulated charges in working PSCs.

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Harnessing chemical functions of ionic liquids for perovskite solar cells Fangfang Fan, Yalan Zhang, Mingwei Hao, Feifei Xin, Zhongmin Zhou, Yuanyuan Zhou 2022, 68(5): 797-810.  DOI: 10.1016/j.jechem.2021.11.038 Abstract ( 13 )   PDF (9226KB) ( 4 )   The remarkable ramping of record power conversion efficiencies in perovskite solar cells (PSCs) has stimulated the growth of this technology towards commercialization. However, there remain challenges and opportunities for further improving their efficiency and stability. Featuring the variety of functional group in the constituting ions, ionic liquids (ILs) exhibit versatile properties and functions that can be leveraged to the development of improved PSCs. Herein with a systematic review on the recent progress in the application of ILs to PSCs, we show that based on the different roles of ILs in the film and device settings, IL can facilitate the thin-film synthesis of perovskites, improve the properties of charge-transport layers, and ameliorate the interfacial energetics at device interfaces. In particular, the ILs-perovskite interactions of two different types (Lewis acid-base interaction and hydrogen bonding) are the essential chemistries underpinning observed efficiency and stability improvements in PSCs, which represent a vast research paradigm in the field of energy chemistry.

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Carbon monoxide production using a steel mill gas in a combined chemical looping process Varun Singh, Lukas C. Buelens, Hilde Poelman, Mark Saeys, Guy B. Marin, Vladimir V. Galvita 2022, 68(5): 811-825.  DOI: 10.1016/j.jechem.2021.12.042 Abstract ( 4 )   PDF (3303KB) ( 3 )   Up to 9% of the global CO2 emissions come from the iron and steel industry. Here, a combined chemical looping process to produce CO, a building block for the chemical industry, from the CO2-rich blast furnace gas of a steel mill is proposed. This cyclic process can make use of abundant Fe3O4 and CaO as solid oxygen and CO2 carriers at atmospheric pressure. A proof of concept was obtained in a laboratory-scale fixed bed reactor with synthetic blast furnace gas and Fe3O4/CaO = 0.6 kg/kg. CO production from the proposed process was investigated at both isothermal conditions (1023 K) and upon imposing a temperature program from 1023 to 1148 K. The experimental results were compared using performance indicators such as CO yield, CO space time yield, carbon recovery of the process, fuel utilisation, and solids’ utilisation. The temperature-programmed CO production resulted in a CO yield of 0.056 ± 0.002 mol per mol of synthetic blast furnace gas at an average CO space time yield of 7.6 mmol kgFe-1 s-1 over 10 cycles, carbon recovery of 48% ± 1%, fuel utilisation of 23% ± 2%, and an average calcium oxide and iron oxide utilisation of 22% ± 1% and 11% ± 1%. These experimental performance indicators for the temperature-programmed CO production were consistently better than those of the isothermal implementation mode by 20% to 35%. Over 10 consecutive process cycles, no significant losses in CO yield were observed in either implementation mode. Process simulation was carried out for 1 million metric tonnes per year of equivalent CO2 emissions from the blast furnace gas of a steel mill to analyse the exergy losses in both modes of operation. Comparison of the exergy efficiency of the temperature-programmed process to the isothermal process showed that the former is more efficient because of the higher CO concentration achievable, despite 20% higher exergy losses caused by heat transfer required to change temperature.

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A photo-assisted electrochemical-based demonstrator for green ammonia synthesis Xiaolu Liu, Zhurui Shen, Xinyue Peng, Lu Tian, Ran Hao, Lu Wang, Yangfan Xu, Yuping Liu, Christos T. Maravelias, Wei Li, Geoffrey A. Ozin 2022, 68(5): 826-834.  DOI: 10.1016/j.jechem.2021.12.021 Abstract ( 9 )   PDF (2587KB) ( 2 )   Bridging laboratory research and practical utilization is of crucial importance for the development of green ammonia synthetic technologies. A decentralized photo-assisted electrochemical-based demonstrator has been proposed for green ammonia synthesis from renewable electricity, air and water, where well-known defect-laden WO3 is used as the working electrode, and a commercially available PV panelsupplies renewable electricity. In this demonstrator, defect-laden WO3 exhibits the optimum electrochemical NH3 formation rate (4.51 × 10-12 mol s-1 cm-2) in 0.1 M K2SO4 in a photovoltaic electrochemical (PV-EC) system. A system-level energy and cost analysis was conducted to investigate its economic viability and a general evaluation tool for system performance and cost estimation was proposed. This advance enables the possibility of integrating the small-scale green ammonia demonstrator into a stand-alone farm system.