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2022, Vol. 72, No. 9　Online: 15 September 2022

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Dinitrogen fixation mediated by lanthanum hydride Hanxue Yan, Wenbo Gao, Jirong Cui, Weijin Zhang, Qijun Pei, Qianru Wang, Yeqin Guan, Sheng Feng, Han Wu, Hujun Cao, Jianping Guo, Ping Chen 2022, 72(9): 1-7.  DOI: 10.1016/j.jechem.2022.04.011 Abstract ( 32 )   PDF (3759KB) ( 12 )   Dinitrogen fixation is one of the key reactions in chemistry, which is closely associated with food, environment, and energy. It has been recently recognized that the hydride materials containing negatively charged hydrogen (H-) show promises for N2 fixation and hydrogenation to ammonia. Herein, we report that rare earth metal hydrides such as lanthanum hydride can also fix N2 either by heating to 200 C or ball milling under ambient N2 pressure and temperature. The N2 fixation by lanthanum hydride may proceed via an intermediate lanthanum hydride-nitride (La-H-N) structure to form the final lanthanum nitride product. The hydride ion functions as an electron donor, which provides electrons for N2 activation possibly mediated by the lanthanum atoms. It is observed that N-H bond is not formed during the N2 fixation process, which is distinctly different from the alkali or alkaline earth metal hydrides. The hydrolysis of La-H-N to ammonia is feasible using water as the hydrogen source. These results provide new insights into the nitrogen fixation by hydride materials and more efforts are needed for the development of rare earth metal-based catalysts and/or nitrogen carriers for ammonia synthesis processes.

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A positive correlation between local photocurrent and grain size in a perovskite solar cell Xiaoxia Zhao, Zhiyong Wang, Wenming Tian, Xianchang Yan, Yantao Shi, Yudi Wang, Zhonggao Sun, Shengye Jin 2022, 72(9): 8-13.  DOI: 10.1016/j.jechem.2022.04.033 Abstract ( 38 )   PDF (2162KB) ( 5 )   Developing an interplay between the local morphological character and its local photovoltaic (PV) parameters in a perovskite thin film is essential for guiding the construction of highly-efficient perovskite solar cells (PSCs). To achieve a higher PSC performance, great efforts have been devoted to the growth of larger perovskite grains; however, how the gain size can influence the PSC performance in a working device remains unclear. Herein, using laser-scanned confocal microscopy coupled with a photocurrent detection module, we realize local photocurrent, photoluminescence (PL) intensity and PL lifetime mappings directly in a working PSC. For perovskite grains of various sizes (from ∼500 nm to a few micrometers), their local photocurrent exhibit a statically positive correlation with the grain size, but anti-correlated with the grain’s local PL intensity. This result suggests that a larger perovskite grain likely has fewer defects and more importantly better interfacial contact with the charge collection layers and thus leads to higher charge collection efficiency, and the optimum grain size is found to be ≥2 μm. Our result provides important guidance to the growth and control of perovskite microstructures toward the further improvement of PSC performance.

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Rapid operando gas monitor for commercial lithium ion batteries: Gas evolution and relation with electrode materials Siqi Lyu, Na Li, Lei Sun, Shuqiang Jiao, Haosen Chen, Wei-Li Song 2022, 72(9): 14-25.  DOI: 10.1016/j.jechem.2022.04.010 Abstract ( 14 )   PDF (12486KB) ( 9 )   Internal gases caused by side reactions are crucial signals for evaluating health and safety states of Li-ion batteries (LIBs) while it is still a great challenge to timely realize accurate monitoring. To address the issues of implanting various gas sensors into commercial batteries, here a novel method is developed to fast operando monitoring gas evolution via equipping non-dispersive infrared multi-gases sensors into a sealed tank, where real commercial batteries with one open end could be settled for operating. The generated CO2 concentration is strongly linked with both voltage and temperature, while the concentrations of CH4 and C2H4 are solely dependent on temperature. As a typical trace gas, evolution behaviors of CO2 have been related to O2 generation from LiNi0.5Mn0.3Co0.2O2 positive electrode, implying stable CO2 release below a critical voltage of 4.5 V. By tracking CO2 concentration, an increased amount of Li2CO3 was monitored on the surface of graphite negative electrode during discharge process at different temperatures and cutoff voltages, which contributes to the component variation of solid electrolyte interfaces. Such operando techniques promise a platform for well understanding the interaction of side reactions linked with gas evolution between positive and negative electrodes in commercial LIBs.

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Etching-courtesy NH4+ pre-intercalation enables highly-efficient Li+ storage of MXenes via the renaissance of interlayer redox Junyan Li, Wei Zhang, Xin Ge, Ming Lu, Xiangxin Xue, Zizhun Wang, Nailin Yue, Junkai Zhang, Xingyou Lang, Qing Jiang, Weitao Zheng 2022, 72(9): 26-32.  DOI: 10.1016/j.jechem.2022.04.030 Abstract ( 9 )   PDF (7004KB) ( 2 )   Inspired by a well-known architecture notion that load-bearing walls enable maintaining a highly-stable multiple-floored building, superior advantages are afforded via fabricating the NH4+ ions pre-intercalated Mo2CTx MXene (Mo2CTx-N) in a mixed solution of NH4F and HCl via a simple one-step hydrothermal method. As a result of the synergistic effects of pillared structure, immobilizing -F groups and unlocking Mo-based redox, the Mo2CTx-N remarkably delivered a reversible capacity of 384.6 mAh g-1 at 200 mA g-1 after 100 cycles. Our work lays a foundation for fully packaging its optimal performance via carding and architecting the chemistry of the MXene layers and between them.

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Gas free oxidation of NaCN for presodiating and stabilizing the anodichost of sodium-ion capacitors Xuexue Pan, Agnieszka Chojnacka, François Béguin 2022, 72(9): 33-40.  DOI: 10.1016/j.jechem.2022.03.024 Abstract ( 15 )   PDF (3045KB) ( 12 )   Sodium-ion capacitors (NICs) trigger considerable attention due to their higher specific energy than elec-trical double-layer capacitors (EDLCs) at comparable specific power. However, the presodiation process of the anodic host is extremely crucial for the construction of high-performance NICs. Herein, a positive EDL electrode containing activated carbon (AC) mixed with sodium cyanide (NaCN) as a sacrificial material was electrochemically oxidized to presodiate a Sn4P3 anodic host buffered by hard carbon (HC). The oxi-dation of CN- occurred ca. 2.9 V vs. Na/Na+ and finished by a short region of linearly increasing potential with a total capacity close to the theoretical value of 547 mAh g-1. The operando electrochemical mass spectrometry (EMS) analysis of the atmosphere in the cell together with the internal pressure measure- ments realized during the galvanostatic oxidation of a YP80F-NaCN electrode demonstrate that the pro- cess occurs without any gas evolution. A precursor cell of an NIC was constructed in a pouch with YP80F- NaCN and HC/Sn4P3 electrodes. After the oxidative sodium transfer from NaCN to HC/Sn4P3, the realized YP80F//Nax(HC/Sn4P3) NIC demonstrated a discharge capacitance retention higher than 80% for 8900 cycles in the voltage range from 2.0 to 3.8 V. The infrared analysis of the anode obtained by the herein described transfer process detected polycyanogen, which stabilizes the electrode structure during cycling, and thereof is at the origin of the enhanced life span of the NIC.

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Revisiting the electrode manufacturing: A look into electrode rheology and active material microenvironment Yan He, Lei Jing, Yuan Ji, Zhiwei Zhu, Lanxiang Feng, Xuewei Fu, Yu Wang 2022, 72(9): 41-55.  DOI: 10.1016/j.jechem.2022.04.038 Abstract ( 26 )   PDF (14104KB) ( 9 )   The microstructures on electrode level are crucial for battery performance, but the ambiguous understand-ing of both electrode microstructures and their structuring process causes critical challenges in controlling and evaluating the electrode quality during fabrication. In this review, analogous to the cell microenviron-ment well-known in biology, we introduce the concept of ‘‘active material microenvironment” (ME@AM) that is built by the ion/electron transport structures surrounding the AMs, for better understanding the sig-nificance of the electrode microstructures. Further, the scientific significance of electrode processing for electrode quality control is highlighted by its strong links to the structuring and quality control of ME@AM. Meanwhile, the roles of electrode rheology in both electrode structuring and structural character-izations involved in the entire electrode manufacturing process (i.e., slurry preparation, coating/printing/extrusion, drying and calendering) are specifically detailed. The advantages of electrode rheology testing on in-situ characterizations of the electrode qualities/structures are emphasized. This review provides a glimpse of the electrode rheology engaged in electrode manufacturing process and new insights into the understanding and effective regulation of electrode microstructures for future high-performance batteries.

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Research progress of precise structural regulation of single atom catalyst for accelerating electrocatalytic oxygen reduction reaction Minmin Wang, Hui Zhang, Yunqi Liu, Yuan Pan 2022, 72(9): 56-72.  DOI: 10.1016/j.jechem.2022.05.007 Abstract ( 16 )   PDF (16920KB) ( 11 )   The development and utilization of renewable clean energy can effectively solve the two major problems of energy and environment. As an efficient power generation device that converts hydrogen energy into elec- tric energy, fuel cell has attracted more and more attention. For fuel cells, the oxygen reduction reaction (ORR) at the cathode is the core reaction, and the design and development of high-performance ORR cata- lysts remain quite challenging. Since the microenvironment of the active center of single atom catalysts (SACs) has an important influence on its catalytic performance, it has been a research focus to improve the ORR activity and stability of electrocatalysts by adjusting the structure of the active center through rea- sonable structural regulation methods. In this review, we reviewed the preparation and structure-activity relationship of SACs for ORR. Then, the structural precision regulation methods for improving the activity and stability of ORR electrocatalysts arediscussed. And the advanced in-situ characterization techniques for revealing the changes of active sites in the electrocatalytic ORR process are summarized. Finally, the chal-lenges and future design directions of SACs for ORR are discussed. This work will provide important refer-ence value for the design and synthesis of SACs with high activity and stability for ORR.

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One-dimensional perovskite-based Li-ion battery anodes with high capacity and cycling stability Hua Kong, Jiafeng Wu, Ying Han, Yu Zhang, Ning Zhou, Qi Chen, Wentao Sun, Huanping Zhou, Lian-Mao Peng 2022, 72(9): 73-80.  DOI: 10.1016/j.jechem.2022.04.021 Abstract ( 6 )   PDF (3786KB) ( 2 )   Perovskite, widely used in solar cells, has also been proven to be potential candidate for effective energy storage material. Recent progress indicates the promise of perovskite for battery applications, however, the specific capacity of the resulting lithium-ion batteries must be further increased. Here, by adjusting the dimensionality of perovskite, we fabricated high-performing one-dimensional hybrid perovskite C4H20N4PbBr6 based lithium-ion batteries, with the first specific capacity as high as 1632.8 mAh g-1 and a stable specific capacity of 598.0 mAh g-1 after 50 cycles under the condition of the constant current density of 150 mA g-1. The stable specific capacity is 2.36 times higher than that of the three-dimensional perovskite CH3NH3PbBr3 (253.2 mAh g-1), and 1.6 times higher than that of the commercialized graphite electrode (372 mAh g-1). The structure difference and the associated ion diffusivity are revealed to sub- stantially affect the specific capacity of the perovskite-based lithium-ion battery. Our study opens up new directions for the applications of hybrid perovskites in energy storage devices.

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Anode reaction mechanisms of Na|NaCl-CaCl2|Zn liquid metal battery Fang Zhang, Jingyun Jin, Junli Xu, Zhongning Shi 2022, 72(9): 81-87.  DOI: 10.1016/j.jechem.2022.04.035 Abstract ( 5 )   PDF (3762KB) ( 2 )   Na|NaCl-CaCl2|Zn liquid metal battery is regarded as a promising energy storage system for power grids. Despite intensive attempts to present a real mechanism of metal electrodes reaction, those for Na||Zn LMBs are not clear yet. Herein, the anode reactions for the multiple discharge potential plateaus were deduced by means of FactSage thermochemical software, which were subsequently validated by X-ray diffraction analysis and the modeling of phase transformation in the cooling process. A pre-treatment process was proposed for the analysis of anode product composition using the atomic absorption spec- trometry method, and the anode states at working temperature (560 °C) were obtained by the Na-Ca-Zn ternary phase for the first time. The results indicate the discharge of Na and Ca led to the formation of Ca-Zn intermetallic compounds, whilst the extraction of Ca in Ca-Zn intermetallic compounds was responsible for the multiple discharge plateaus. Moreover, it was found that the charging product was in electrochemical double liquid metal layers, which are composed of Na and Ca with dissolved Zn respectively.

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Urea electrooxidation-boosted hydrogen production on nitrogen-doped porous carbon nanorod-supported nickel phosphide nanoparticles Xiaoyu Zhang, Ge Ma, Lingling Shui, Guofu Zhou, Xin Wang 2022, 72(9): 88-96.  DOI: 10.1016/j.jechem.2022.04.045 Abstract ( 16 )   PDF (4404KB) ( 8 )   Urea electro-oxidation reaction (UEOR)-boosted water electrolysis can supplant the kinetics-restricted oxygen evolution reaction (OER) and provide an energy-saving method of hydrogen generation. However, low UEOR activity and the poisoning issue of the catalyst limit its practical application. Herein, a simple coordination reaction is used to synthesize the dimethylglyoxime-NiⅡ complex (DMG-NiⅡ), which efficiently serves as the initial precursor to synthesize nitrogen-doped carbon nanorod- supported nickel phosphide nanoparticle (Ni2P/N-Cnanorods) nanocomposites. The density functional the-ory calculations and electrochemical results reveal that nitrogen doping can weaken the adsorption of hydrogen and the generated CO2, resulting in an enhancement of hydrogen evolution reaction (HER) and UEOR activity. In addition, N-doping can also promote the generation of Ni3+, which can further pro-mote the UEOR and HER performance. Concretely, the overpotential for the HER on Ni2P/N-Cnanorods-2h nanocomposites is only 201 mV at 10 mA cm-2, and the onset potential of the UEOR on Ni2P/N- Cnanorods-2h nanocomposites is only 1.34 V. Additionally, the Ni2P/N-Cnanorods nanocomposites also show excellent long-term stability due to the introduction of nitrogen-doped carbon material. Consequently, the symmetric Ni2P/N-Cnanorods-2h||Ni2P/N-Cnanorods-2h urea electrolyzer requires 1.41 V of electrolysis voltage for urea electrolysis, which can be applied in energy-saving H2 production and environment purification.

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Tailoring carbon chains for repairing graphite from spent lithium-ion battery toward closed-circuit recycling Chenxing Yi, Peng Ge, Xiqing Wu, Wei Sun, Yue Yang 2022, 72(9): 97-107.  DOI: 10.1016/j.jechem.2022.05.002 Abstract ( 17 )   PDF (18522KB) ( 8 )   Graphite, as a strategic mineral resource, the recycling from spent lithium-ion batteries (LIBs) has attracted considerable attention for meeting considerable economic value. However, closed-circuit recy- cling still suffers from the lack of effective repair methods. Considering the existing defects, a series of C- chain length carbons have been successfully introduced to repair spent graphite. Obviously, with the evo- lution of carbon resources, the thickness and pores of the coating layer were tailored with the functional groups. Benefitting from the increased active sites and created fold structure, their coulombic efficiency is obviously restored from 14% to 86.89%, while the stable capacity is kept at approximately 384.9 mAh g-1 after 100 cycles. Moreover, their excellent rate properties are kept about approximately 200 mAh g-1 at 2 C, meeting the standard of commercial materials. Supported by the detailed kinetic behaviors, the enhanced rate is mainly dominated by pseudocapacitive behaviors, accompanied by deepening redox reactions. Meanwhile, the cost of the proposed approach for recycling spent graphite is 894.87 $ t-1, and the recycling profit for regenerating graphite is approximately 7000 $ t-1. Given this, this work is anticipated to shed light on the closed-circuit recycling of spent graphite and offer significant strategies to repair graphite.

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Ultra-fast phosphating synthesis of metastable crystalline phase-controllable ultra-small MPX/CNT (M = Pd, Pt, Ru) for polyalcohol electrooxidation Yan Zhang, Dan Zhang, Yingnan Qin, Juan Xiong, Jiao Liu, Wenhao Yu, Xilei Chen, Suping Li, Jianping Lai, Lei Wang 2022, 72(9): 108-115.  DOI: 10.1016/j.jechem.2022.05.001 Abstract ( 9 )   PDF (6323KB) ( 2 )   A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small (<5 nm) noble metal phosphides (MPX/CNT, M = Pd, Pt, Ru) which are successfully produced in just 75 s for the first time. The catalytic performance of the catalysts can be optimized by controlling the nanomaterials as the metastable crystalline phases. By altering the phosphorus source under the same conditions, the hexagonal structured Pd7P3 (NaH2PO2ÁH2O as P source) and monoclinic structured Pd6P (Na4P2O7 as P source) can be prepared successfully. Both of them exhibit excellent polyol oxidation performance in alkaline media. Monoclinic Pd6P/CNT and hexagonal Pd7P3/CNT have large ECSA which are confirmed as 82.1 m2 g-1 and 86.2 m2 g-1, respectively. Hexagonal Pd7P3/CNT has the highest mass activity of 6.14 A mgP-d1 (3.21 A mg-Pd1 for Pd6P/CNT) for GOR, which far exceeded Pt/C (2.81 A mg-Pt1). Meanwhile, the mass activity of monoclinic Pt5P2/CNT for EGOR achieved 12.4 A mgP-t1, which far exceeded Pt/C (6.8 A mgP-t1). The stability test proved that the activity decay of these catalysts was negligible after the 12-hour durability test. Meanwhile, they have excellent CO anti-poisoning abilities.

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Ordered mesoporous carbon spheres assisted Ru nanoclusters/RuO2 with redistribution of charge density for efficient CO2 methanation in a novel H2/CO2 fuel cell Yan Liu, Tao Zhang, Chao Deng, Shixiu Cao, Xin Dai, Shengwu Guo, Yuanzhen Chen, Qiang Tan, Haiyan Zhu, Sheng Zhang, Yongning Liu 2022, 72(9): 116-124.  DOI: 10.1016/j.jechem.2022.04.051 Abstract ( 10 )   PDF (8014KB) ( 3 )   Efficiently reducing carbon dioxide (CO2) into carbon chemicals and fuels is highly desirable due to the rapid growth of atmospheric CO2 concentration. In prior work, we described a unique H2/CO2 fuel cell dri- ven by low-valued waste heat, which not only converts CO2 to methane (CH4) but also outputs electrical energy, yet the CO2 reduction rate needs to be urgently improved. Here, a novel Ru-RuO2 catalyst with heterostructure was grafted on mesoporous carbon spheres by in situ partially reducing RuO2 into ultra-small Ru clusters (~1 nm), in which heteroatom-doped carbon spheres as a matrix with excellent con-ductivity and abundant pores can not only easily confine the formation of Ru nanocluster but also are beneficial to the exposed active sites of Ru complex and the mass transport. Compared to pure RuO2 nanoparticles supported on carbon spheres, our composite catalyst boosts the CO2 conversion rate by more than 5-fold, reaching a value of 382.7 lmol gcat.-1 h-1 at 170 ℃. Moreover, a decent output power den- sity of 2.92 W m-2 was obtained from this H2/CO2 fuel cell using Ru-RuO2 embedded carbon spheres as a cathode catalyst. The Ru-RuO2 heterostructure can modify the adsorption energy of CO2 and induce the redistribution of charge density, thus boosting CO2 reduction significantly. This work not only offers an efficient catalyst for this novel H2/CO2 fuel cell but also presents a facile method to prepare Ru nanoclusters.

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Regulating local charges of atomically dispersed Moδ+ sites by nitrogen coordination on cobalt nanosheets to trigger water dissociation for boosted hydrogen evolution in alkaline media Maoqi Cao, Kang Liu, Yao Song, Chao Ma, Yiyang Lin, Huangjingwei Li, Kejun Chen, Junwei Fu, Hongmei Li, Jun Luo, Yida Zhang, Xusheng Zheng, Junhua Hu, Min Liu 2022, 72(9): 125-132.  DOI: 10.1016/j.jechem.2022.04.046 Abstract ( 7 )   PDF (7695KB) ( 2 )   Now, Pt-based materials are still the best catalysts for hydrogen evolution reaction (HER). Nevertheless, the scarcity of Pt makes it impossible for the large-scale applications in industry. Although cobalt is taken as an excellent HER catalyst due to its suitable H* binding, its alkali HER catalytic property need to be improved because of the sluggish water dissociation kinetics. In this work, nitrogen with small atomic radius and metallophilicity is employed to adjust local charges of atomically dispersed Moδ+ sites on Co nanosheets to trigger water dissociation. Theoretical calculations suggest that the energy barrier of water dissociation can be effectively reduced by introducing nitrogen coordinated Moδ+ sites. To realize this speculation, atomically dispersed Moδ+ sites with nitrogen coordination of Mo(N)/Co were prepared via reconstruction of CoMoO4. High angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption spectroscopy (XAS) demonstrate the coordination of N atoms with atomically dispersed Mo atoms, leading to the local charges of atomically dispersed Moδ+ sites in Mo(N)/ Co. The measurement from ambient pressure X-ray photoelectron spectroscopy (AP-XPS) reveals that the Moδ+ sites promote the adsorption and activation of water molecule. Therefore, the Mo(N)/Co exhibits an excellent activity, which need only an overpotential of 39 mV to reach the current density of 10 mA cm-2. The proposed strategy provides an advance pathway to design and boost alkaline HER activity at the atomic-level.

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Understanding the phenomenon of capacity increasing along cycles: In the case of an ultralong-life and high-rate SnSe-Mo-C anode for lithium storage Xin Wu, Xingyu Xiong, Bin Yuan, Jun Liu, Renzong Hu 2022, 72(9): 133-142.  DOI: 10.1016/j.jechem.2022.05.003 Abstract ( 8 )   PDF (10797KB) ( 3 )   A good cycling stability is a prerequisite for the application of metal-based materials in lithium-ion bat- teries (LIBs). However, an abnormal increase in capacity is often observed, which has rarely been focused on in many studies. In our SnSe-Mo-C composite anode, a high reversible capacity of 737.4 mAh g-1 remained after 5000 cycles at 5 A g-1 between 0.01 and 3.0 V versus Li/Li+. However, a continuous capac-ity increase occurred in the initial cycles, with 1086.9 mAh g-1 after 1000 cycles and 1216.9 mAh g-1 after 1500 cycles, respectively. Further studies revealed that the electrolyte decomposed at high poten- tials (2.5-3.0 V) and provided additional capacities. The cut-off voltage and electrolyte filling were con- trolled, which eliminated the impact of electrolyte decomposition, prevented rapid capacity decay, and provided a stable cycling performance for SnSe-Mo-C anodes in LIBs. This work shows that the composite anode is promising for lithium storage and the findings provide new insights into understanding and con- trolling the phenomenon of capacity increase with cycling in metal-based anode materials.

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Stable and dendrite-free Zn anode with artificial desolvation interface layer toward high-performance Zn-ion capacitor Zhe Gong, Kai Jiang, Pengfei Wang, Xunliang Liu, Dashuai Wang, Ke Ye, Kai Zhu, Jun Yan, Guiling Wang, Dianxue Cao 2022, 72(9): 143-148.  DOI: 10.1016/j.jechem.2022.05.017 Abstract ( 8 )   PDF (5395KB) ( 2 )   Aqueous Zn-based energy storage devices possess tremendous advantages, such as low cost, high safety, and competitive energy density, due to employing a Zn metal anode and aqueous electrolyte. However, the cycling stability and rate ability of a Zn anode are hindered by Zn dendrite growth and sluggish ion transfer in the electrode/electrolyte interface. Herein, the interfacial properties of Zn anodes are improved through the introduction of a silver (Ag) protective layer, which facilitates uniform Zn deposi-tion and regulates Zn ion transport. As a result, Ag-coated Zn anodes display stable cycling performance (600 h at 1 mA cm-2) and low overpotential (150 mV at 50 mA cm-2 after 2000 cycles). The Ag layer in situ electrochemically converts into an AgZn3 layer and promotes Zn ion desolvation and three-dimensional diffusion processes. Moreover, a Zn-ion capacitor assembled with an Ag-coated Zn anode and active carbon cathode shows a capable cycling lifespan and rate performance. This study provides a feasible strategy for constructing a stabilized and dendrite-free Zn anode for the development of high-performance Zn-based energy storage devices.

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Powder metallurgical 3D nickel current collectors with plasma-induced Ni3N nanocoatings enabling long-life and dendrite-free lithium metal anode Piao Qing, Zhibin Wu, Yuejiao Chen, Fengcheng Tang, Hao Yang, Libao Chen 2022, 72(9): 149-157.  DOI: 10.1016/j.jechem.2022.05.020 Abstract ( 12 )   PDF (10653KB) ( 2 )   Building three-dimensional (3D) current collectors is a promising strategy to surmount the bottlenecks of lithium metal anodes (LMAs), but the regulation methodology of a 3D current collector has seldom been considered comprehensively concerning both skeleton architectures and surface coatings. Herein, a robust porous 3D nickel skeleton (NS) with lithiophilic Ni3N nanocoatings (Ni3N@NS) is synthesized via an integrative route of powder metallurgy/plasma-enhanced nitridation technics. The facile powder metallurgical method facilitates the adjustment of NS architectures toward sufficient electrolyte adsorp-tion and even current density distribution, while the followed plasma-enhanced chemical vapor deposi-tion (PECVD) method can induce compact Ni3N nanocoatings on NS, which reduces the Li nucleation overpotential, accelerates the Li-ion transfer, and facilitates a highly reversible oriented texture of Li deposition morphology owing to the dense and homogenous deposition of Li into the pores. The opti- mized Ni3N@NS current collector shows a high averaged Coulombic efficiency (CE) of 98.8% over 350 cycles, a prolonged lifespan of 1000 h (at 2 mA cm-2) in symmetrical cells, together with the significant performance in full cells. The ingenious methodology reported in this work can also be broadly applicable for the controllable production of other 3D skeletons with nitride nanocoatings for various applications.

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Thermal safety of dendritic lithium against non-aqueous electrolyte in pouch-type lithium metal batteries Feng-Ni Jiang, Shi-Jie Yang, Xin-Bing Cheng, Peng Shi, Jun-Fan Ding, Xiang Chen, Hong Yuan, Lei Liu, Jia-Qi Huang, Qiang Zhang 2022, 72(9): 158-165.  DOI: 10.1016/j.jechem.2022.05.005 Abstract ( 36 )   PDF (5137KB) ( 19 )   A quantitative relationship between safety issues and dendritic lithium (Li) has been rarely investigated yet. Herein the thermal stability of Li deposits with distinct surface area against non-aqueous electrolyte in pouch-type Li metal batteries is probed. The thermal runaway temperatures of Li metal batteries obtained by accelerating rate calorimeter are reduced from 211 °C for Li foil to 111 °C for cycled Li. The initial exothermic temperature is reduced from 194 °C for routine Li foil to 142 °C for 49.5 m2 g-1 dendrite. Li with different specific surface areas can regulate the reaction routes during the temperature range from 50 to 300 °C. The mass percent of Li foil and highly dendritic Li reacting with ethylene car- bonate is higher than that of moderately dendritic Li. This contribution can strengthen the understanding of the thermal runaway mechanism and shed fresh light on the rational design of safe Li metal batteries.

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Lithium film with abundant stepped structures: A promising route for homogeneous Li ion deposition to conquer lithium dendrite issue and its action mechanism Yong Zhang, Shu-Qin Song, Yong Gao, Tian-Fu Liu, Hong Zhao 2022, 72(9): 166-175.  DOI: 10.1016/j.jechem.2022.04.036 Abstract ( 6 )   PDF (9937KB) ( 9 )   Lithium is considered to be the "holy grail" for the application of energy storage due to its highest the- oretical capacity and lowest anode potential. However, one of the grand difficulties in the development of lithium-based batteries is the lithium dendrite growth that leads to capacity fading and electrode degradation over long-term cycling. Compared with conventional electrolyte modifications, artificial solid electrolyte interfaces (SEI) synthesis and framework designing approaches, tuning surface morphol- ogy of lithium anode is the direct route to induce homogeneous Li ion deposition. Due to the high chem- ical activity of lithium metal, however, controllable growth of lithium micro/nanostructures by traditionally chemical approaches is still a big challenge. Herein, we have developed a facile compression route to fabricate lithium anode with abundant stepped lithium structures. The electrochemical results demonstrate that the dendritic growth issue is effectively suppressed by orderly arranged stepped lithium structures. After 90 cycles, a high discharge capacity of 954 mAh g-1 is achieved, which is 2.7 times that of the uncompressed lithium anode (342 mAh g-1). First-principles calculations reveal that the orderly arranged stepped lithium structures are lithiophilic active sites to adsorb Li ion, which con- tributes to homogeneous deposition of Li ion on lithium anode, eventually solving the lithium dendrite issue. This work paves a new road to suppress dendritic growth, which will provide some new ideas to design long recycling sodium, potassium and zinc, and other metal anode batteries.

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Scalable synthesis of hcp ruthenium-molybdenum nanoalloy as a robust bifunctional electrocatalyst for hydrogen evolution/oxidation Zhen Zhang, Haijun Liu, Liwen Ni, Zhi-Liang Zhao, Hui Li 2022, 72(9): 176-185.  DOI: 10.1016/j.jechem.2022.04.043 Abstract ( 8 )   PDF (8679KB) ( 4 )   The hydrogen evolution reaction (HER) is the cathodic process of water splitting, and its reverse, the hydrogen oxidation reaction (HOR), is the anodic process of an H2-O2 fuel cell; both play important roles in the development of hydrogen energy. The rational design and scalable fabrication of low-cost and effi-cient bifunctional catalysts for the HER/HOR are highly desirable. Herein, ultrasmall Mo-Ru nanoalloy (Mo0.5Ru3 and MoRu3) particles uniformly distributed on mesoporous carbon (MPC) were successfully synthesized by a simple method that is easy to scale up for mass production. After the incorporation of Mo atoms, the as-prepared Mo0.5Ru3 and MoRu3 nanoalloys maintain a hexagonal-close-packed crystal structure. In acidic media, Mo0.5Ru3 exhibits excellent Pt-like HER and HOR activity, as well as good sta-bility. Density functional theory (DFT) calculations reveal that the H adsorption free energy (DGH*) on the Mo0.5Ru3 (0 0 1) surface (-0.09 eV) is much closer to zero than that of metallic Ru (-0.22 eV), which con-tributes to the enhanced catalytic activity. In alkaline media, Mo0.5Ru3 also presents outstanding HER and HOR activity, even significantly outperforming Pt/C. The DFT results confirm that optimal binding ener-gies with H* and OH* intermediate species, and low energy barriers in the water dissociation and forma- tion steps, efficiently accelerate the alkaline HER/HOR kinetics of Mo0.5Ru3. This study provides a new avenue for the scalable fabrication of high-efficiency bifunctional electrocatalysts for the HER and HOR in both acidic and alkaline media.

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A robust interphase via in-situ pre-reconfiguring lithium anode surface for long-term lithium-oxygen batteries Pan Xu, Xiaodong Lin, Zongqiang Sun, Kaixuan Li, Wenjie Dou, Qing Hou, Zhiyou Zhou, Jiawei Yan, Mingsen Zheng, Ruming Yuan, Quanfeng Dong 2022, 72(9): 186-194.  DOI: 10.1016/j.jechem.2022.04.025 Abstract ( 7 )   PDF (8000KB) ( 3 )   Lithium-oxygen (Li-O2) battery is considered as one of the most promising alternatives because of its ultrahigh theoretical energy density. However, their cycling stability is severely restricted by the uncon- trollable dendrite growth and serious oxygen corrosion issue on Li surface. Herein, a sulfur-modified Li surface can be successfully constructed via chemical reaction of guanylthiourea (GTU) molecule on Li, which can induce the selectively fast decomposition of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to form a smooth and stable inorganics-rich solid-electrolyte interphase (IR-SEI) during the sub- sequent electrochemical process. Such an IR-SEI cannot only offer a highly reversible and stable Li plat- ing/stripping chemistry with dendrite-free property (10 mA cm-2-10 mAh cm-2, > 0.5 years; 3 mA cm-2-3 mAh cm-2, > 1 year) but also endows the Li metal an anti-oxygen corrosion function, thereby signifi- cantly improving the cycling stability of Li-O2 batteries. This work provides a new idea for constructing functional solid-electrolyte interphase (SEI) to achieve highly stable Li metal anode.

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Low-temperature and high-voltage planar micro-supercapacitors based on anti-freezing hybrid gel electrolyte Manning Chen, Xiaoyu Shi, Xiaolei Wang, Hanqing Liu, Sen Wang, Caixia Meng, Yu Liu, Liangzhu Zhang, Yuanyuan Zhu, Zhong-Shuai Wu 2022, 72(9): 195-202.  DOI: 10.1016/j.jechem.2022.04.029 Abstract ( 7 )   PDF (6376KB) ( 5 )   Micro-supercapacitors (MSCs) are considered as highly competitive power sources for miniaturized elec-tronics. However, narrow voltage window and poor anti-freezing properties of MSCs in conventional aqueous electrolytes lead to low energy density and limited environmental adaption. Herein, we report the construction of low-temperature and high-energy-density MSCs based on anti-freezing hybrid gelelectrolytes (HGE) through introducing ethylene glycol (EG) additives into aqueous LiCl electrolyte. Since EG partially destroys hydrogen bond network among water molecules, the HGE exhibits maximum electrochemical stability window of 2.7 V and superior anti-freezing features with a glass transition tem- perature of -62.8 °C. Further, the optimized MSCs using activated carbon microelectrodes possess impressive volumetric capacitance of 28.9 F cm-3 and energy density of 10.3 mWh cm-3 in the voltage of 1.6 V, 2.6 times higher than MSCs tested in 1.2 V. Importantly, the MSCs display 68.3% capacitance retention even at -30 °C compared to the value at 25 °C, and ultra-long cyclability with 85.7% of initial capacitance after 15,000 times, indicating extraordinary low-temperature performance. Besides, our devices offer favorable flexibility and modular integration. Therefore, this work provides a general strat-egy of realizing flexible, safe and anti-freezing microscale power sources, holding great potential towards subzero-temperature microelectronic applications.

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D-band frontier: A new hydrogen evolution reaction activity descriptor of Pt single-atom catalysts Guangming Zhan, Yancai Yao, Fengjiao Quan, Huayu Gu, Xiao Liu, Lizhi Zhang 2022, 72(9): 203-209.  DOI: 10.1016/j.jechem.2022.05.012 Abstract ( 7 )   PDF (7812KB) ( 3 )   Hydrogen evolution reaction (HER) is crucial for achieving sustainable development and carbon neutrality, and thus demands efficient catalysts, which necessitates fundamental theory to relieve trial-and-error experiment. To fast screen HER candidates, most studies focus on d-band center (ed) associated with the Gibbs energy of H* adsorption (DGH*). Unfortunately, ed rule is not applicable to Pt single atoms on transition metal disulfides (Pt1/TMDs) because of the additional contributions from p states of S atom. Here, we propose a new HER descriptor — d-band frontier (df) by defining the weight of d-band in the energy range of [-1.0 eV, 1.0 eV] of Pt single atoms. This df is exactly correlated with the DGH* of Pt1/TMDs, and thus perfectly describes the structure-activity relationship, as validated by systematical experimental evidences. Moreover, this df descriptor can be extended to Pt single atoms anchored on other supports (e.g., C3N4, C, MoO3, and CoO), indicating its promising generality.

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Disclosing the active integration structure and robustness of a pseudo-tri-component electrocatalyst toward alkaline hydrogen evolution Hong-Hong Zou, Wan-Qing Li, Cong-Hu Song, Li-Ming Cao, Xue-Feng Zhang, Xuan-Yi Zhu, Zi-Yi Du, Jia Zhang, Sheng-Liang Zhong, Chun-Ting He 2022, 72(9): 210-216.  DOI: 10.1016/j.jechem.2022.03.038 Abstract ( 3 )   PDF (6498KB) ( 2 )   Designing multicomponent integration catalysts (MICs) has been a promising strategy for improving electrocatalytic hydrogen evolution reaction (HER) due to the highly active interfaces as well as electronic synergy. Nevertheless, many fundamental questions such as their actual active species and the influence on long-term stability remain to be answered. Herein, we present the structural evolution from a pseudo-tri-component electrocatalyst of nitrogen-doped carbon supported nickel/vanadium nitride/vanadium oxide (Ni-VN-V2O3/NC) nanorods to the heterostructural nickel/vanadium nitride (Ni-VN/NC) nanosheets during chemical or electrochemical processes. The self-reconstructed Ni-VN/NC exhibits a robust stability under alkaline conditions, while maintaining initial efficient HER activity with a low overpotential of 76 mV at the current density of 10 mA cm-2. Theoretical calculations and quasi-in-situ spectroscopic technology unveil the redistribution of electrons on the synergistic active interface, which synchronously optimizes the affinities for hydrogen, hydroxide, and water molecules, thereby remarkably accelerating the HER kinetics by reducing the barrier of Volmer step.

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Catalyst activation: Surface doping effects of group VI transition metal dichalcogenides towards hydrogen evolution reaction in acidic media Bibi Ruqia, Mrinal Kanti Kabiraz, Jong Wook Hong, Sang-Il Choi 2022, 72(9): 217-240.  DOI: 10.1016/j.jechem.2022.04.023 Abstract ( 12 )   PDF (31723KB) ( 9 )   Two-dimensional (2D) transition metal dichalcogenides (TMDs) have emerged as promising alterna-tives to the platinum-based catalysts for hydrogen evolution reaction (HER). The edge site of these 2D materials exhibits HER-active properties, whereas the large-area basal plane is inactive. Therefore, recent studies and methodologies have been investigated to improve the performance of TMD-based materials by activating inactive sites through elemental doping strategies. In this review, we focus on the metal and non-metal dopant effects on group VI TMDs such as MoS2, MoSe2, WS2, and WSe2 for promoting HER performances in acidic electrolytes. A general introduction to the HER is initially provided to explain the parameters in accessing the catalytic performance of doped- TMDs. Then, synthetic methods for doped-TMDs and their HER performances are introduced in order to understand the effect of various dopants including metallic and non-metallic elements. Finally, the current challenges and future opportunities are summarized to provide insights into developing highly active and stable doped-TMD materials and valuable guidelines for engineering TMD-based nanocatalysts for practical water splitting technologies.

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Explosion behavior investigation and safety assessment of large-format lithium-ion pouch cells Tongxin Shan, Zhenpo Wang, Xiaoqing Zhu, Hsin Wang, Yangjie Zhou, Yituo Wang, Jinghan Zhang, Zhiwei Sun 2022, 72(9): 241-257.  DOI: 10.1016/j.jechem.2022.04.018 Abstract ( 7 )   PDF (13305KB) ( 2 )   Large-format lithium-ion (Li-ion) batteries with high energy density for electric vehicles are prone to thermal runaway (or even explosion) under abusive conditions. In this study, overcharge induced explo- sion behaviors of large-format Li-ion pouch cells with Li[Ni0.8Co0.1Mn0.1]O2 cathode at different current rates (C-rates) (0.5C, 1C, 2C) were investigated. The explosion characteristics of the cells were elucidated by discussing the evolution of the cell voltage, the surface temperature and the shock wave pressure. Generally, the whole overcharge process could be divided into four stages according to the evolution of several key parameters and the overcharge behaviors; the overcharge C-rate has a great influence on cells’ thermal behaviors. The experimental results showed that the thermal runaway process of Li-ion cells caused by overcharging consisted of two kinds of explosions, physical explosion and chemical explosion. The existence of observable negative pressure zone in the pressure curves indicated that the Li-ion cells are not a self-supplying oxygen system during the explosion. Further, the explosion dynamics parameters were matched. An explosion TNT-equivalent conversion strategy that depended on the pres-sure of the shock wave was utilized to evaluate the released energy and its hazards. In addition, with respect to the overcharge of Li-ion pouch cells, a safety assessment method and a safety management method were proposed based on the explosion behaviors. From the perspective of battery safety, this study is of great significance for the safety design of Li-ion cells and can provide guidance for engineers to optimize the safety function of battery packs.

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Dynamic chemical processes on ZnO surfaces tuned by physisorption under ambient conditions Yunjian Ling, Jie Luo, Yihua Ran, Yunjun Cao, Wugen Huang, Jun Cai, Zhi Liu, Wei-Xue Li, Fan Yang, Xinhe Bao 2022, 72(9): 258-264.  DOI: 10.1016/j.jechem.2022.03.009 Abstract ( 12 )   PDF (3435KB) ( 9 )   The catalytic properties of non-reducible metal oxides have intrigued continuous interest in the past dec-ades. Often time, catalytic studies of bulk non-reducible oxides focused on their high-temperature appli-cations owing to their weak interaction with small molecules. Hereby, combining ambient-pressure scanning tunneling microscopy (AP-STM), AP X-ray photoelectron spectroscopy (AP-XPS) and density functional theory (DFT) calculations, we studied the activation of CO and CO2 on ZnO, a typical non-reducible oxide and major catalytic material in the conversion of C1 molecules. By visualizing the chem-ical processes on ZnO surfaces at the atomic scale under AP conditions, we showed that new adsorbate structures induced by the enhanced physisorption and the concerted interaction of physisorbed mole-cules could facilitate the activation of CO and CO2 on ZnO. The reactivity of ZnO towards CO could be observed under AP conditions, where an ordered (2 - 1)-CO structure was observed on ZnOð1010Þ. Meanwhile, chemisorption of CO2 on ZnOð1010Þ under AP conditions was also enhanced by physisorbed CO2, which minimizes the repulsion between surface dipoles and causes a (3 - 1)-CO2 structure. Our study has brought molecular insight into the fundamental chemistry and catalytic properties of ZnO sur-faces under realistic reaction conditions.

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New insight on correlation between the electrochemical stability and the thermal stability of high nickel cathode materials Lifan Wang, Rui Wang, Cong Zhong, Liangtao Lu, Danya Gong, Qinling Shi, Yujie Fan, Xindong Wang, Chun Zhan, Guicheng Liu 2022, 72(9): 265-275.  DOI: 10.1016/j.jechem.2022.04.006 Abstract ( 10 )   PDF (10002KB) ( 1 )   Cycle stability and thermal safety are critical to the commercialization of nickel-rich layered materials, yet whether there is a potential correlation between these two factors is still controversial. Herein, the relationship between the cycle stability and thermal stability of nickel-rich cathode materials have been systematically studied through five different calcination temperatures of Li[Ni0.83Co0.12Mn0.05]O2 (NCM83) cathode materials. The research results confirm that the cycle stability and thermal safety of nickel-rich cathode materials do not necessarily show a positive correlation. Actually, with the calcina-tion temperature elevated, the thermal stability of the NCM83 is enhanced, while the cycle stability is degraded. This opposite correlation is not commonly reported in previous literatures. In this work, sys-tematical characterizations demonstrate that under the experimental conditions, the capacity retention of NCM83 is mainly determined by the Li/Ni cation disorder and H2-H3 irreversible phase transition, which is optimal at lower calcination temperature. Meanwhile, the thermal stability is mainly impacted by thermal expansion characteristics and interfacial stability of cathode material, and it is dramatically improved by the mechanical strength of the secondary particles reinforced at high calcinated tempera-ture. This study provides some new insights on understanding and designing of the high-energy cathode materials with long cycle-life and superior safety.

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P-functionalized carbon nanotubes promote highly stable electrocatalysts based on Fe-phthalocyanines for oxygen reduction: Experimental and computational studies Beatriz Martínez-Sánchez, Diego Cazorla-Amorós, Emilia Morallón 2022, 72(9): 276-290.  DOI: 10.1016/j.jechem.2022.05.024 Abstract ( 13 )   PDF (10760KB) ( 4 )   Iron(II) phthalocyanines (FePc) supported on functionalized nanostructured carbon materials have been studied as electrocatalysts for the oxygen reduction reaction (ORR) in an alkaline medium. Herein, two types of carbon nanotubes (CNTs) have been explored as support, Single-Walled Carbon Nanotubes and Herringbone Carbon Nanotubes (SWCNTs and hCNTs, respectively), both electrochemically modified with ortho- aminophenylphosphonic acid (2APPA), which provides phosphate axial coordinating ligands for the immobilization of FePc molecules. All the catalysts were prepared via a facile incipient wetness impregnation method. Comprehensive experimental analysis together with density functional theory (DFT) calculations has demonstrated both the importance of the five-coordinated Fe macrocycles that favor the interaction between the FePc and the carbon support, as well as the effect of the CNT structure in the ORR. FePc axial coordination provides a better dispersion, leading to higher stability and a favor-able electron redistribution that also tunes the ORR performance by lowering the stability of the reaction intermediates. Interestingly, such improvement occurs with a very low content of metal (~1 wt% Fe), which is especially remarkable when hCNT support is employed. This work provides a novel strategy for the development of Fe-containing complexes as precious metal-free catalysts towards the ORR.

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Correlation between self-discharge behavior and heteroatoms over doped carbon sheets for enhanced pseudocapacitance Kunlun Liu, Chang Yu, Yuanyang Xie, Wei Guo, Jinhe Yu, Lin Ni, Zhao Wang, Rong Fu, Jieshan Qiu 2022, 72(9): 291-298.  DOI: 10.1016/j.jechem.2022.05.004 Abstract ( 7 )   PDF (2634KB) ( 7 )   For electric double layer supercapacitors, carbon materials originating from the purely physical energy- storage mechanism limit the improvement in the capabilities of charge storage. To solve this problem, doping heteroatoms into carbon skeleton is a promising & charming strategy for enhancing electrochem- ical performance by providing the extra pseudocapacitance. However, the self-discharge behavior of such heteroatom-doped supercapacitors has been a challenging issue for a long time. Here, the porous carbon nanosheets with a tunable total content of heteroatoms are chosen as a demo to systemically decouple the correlation between the total content of heteroatoms and the specific capacitance as well as the self-discharge behavior. The capacitance changes in a range of 164-331 F g-1 @1 A g-1 with the increased total contents of doped heteroatom, strongly dependent on and sensitive to the total content of heteroa-toms. The voltage retention rate and capacitance retention rate for the porous carbon nanosheets with a tunable total content of heteroatoms completely present a quick decline tendency as the increase in the content of heteroatoms, changing from 58% to 34% and 74% to 39%, respectively, indicative of a linear neg-ative relationship. More importantly, the self-discharge mechanisms are elaborately explored and follow the combination of activation- and diffusion-controlled Faradic reactions. This work illustrates the diverse impacts of the doped heteroatoms on the electrochemical performance of supercapacitors, cov-ering specific capacitance and self-discharge behavior, and highlights the importance of balancing the contents of doped heteroatoms in energy storage fields.

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Cascade adsorptive separation of light hydrocarbons by commercial zeolites Shanshan Liu, Yinlin Chen, Bin Yue, Yuanxin Nie, Yuchao Chai, Guangjun Wu, Jiangnan Li, Xue Han, Sarah J. Day, Stephen P. Thompson, Naijia Guan, Sihai Yang, Landong Li 2022, 72(9): 299-305.  DOI: 10.1016/j.jechem.2022.05.023 Abstract ( 6 )   PDF (4846KB) ( 3 )   Adsorptive separation of light hydrocarbons by porous solids provides an energy-efficient alternative to state-of-the-art cryogenic distillation. However, an optimal balance between the cost, performance and stability of the sorbent material is yet to be achieved for industrial applications. Here, we report the efficient separation of C2 and C3 hydrocarbons by a faujasite zeolite (Na-X, Si/Al = 1.23). A tandem configuration of two fixed-beds packed with Na-X affords complete dynamic separation of the ternary mixture of C2H2/C2H4/C2H6 (1/49.5/49.5; v/v/v) under ambient conditions. Pressure-swing desorption on the latter fixed-bed gives ethylene (>99.50%, 1.80 mmol g-1) and ethane (>99.99%, 1.41 mmol g-1). In situ synchrotron X-ray powder diffraction revealed the binding sites for C2H2 and C2H4 in Na-X. This study highlights the potential application of commercial zeolites for challenging industrial separations.

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Active and stable Cu doped NiMgAlO catalysts for upgrading ethanol to n-butanol Zhinuo Wang, Ming Yin, Jifeng Pang, Xianquan Li, Yanan Xing, Yang Su, Shimin Liu, Xiaoyan Liu, Pengfei Wu, Mingyuan Zheng, Tao Zhang 2022, 72(9): 306-317.  DOI: 10.1016/j.jechem.2022.04.049 Abstract ( 12 )   PDF (9134KB) ( 4 )   Upgrading ethanol to n-butanol is an attractive way for renewable n-butanol production. Herein, Cu was selected to modify NiMgAlO catalysts for improving ethanol conversion and n-butanol selectivity. Over the optimized 2%Cu-NiMgAlO catalyst, ethanol conversion and n-butanol selectivity were enhanced to 30.0% and 64.2%, respectively, in 200 h time on stream at 523 K. According to physicochemical character- izations and theoretical calculations, the key role of multiple active sites in this reaction was extensively investigated. The plate-like structure of hydrotalcite was maintained over 2% Cu-NiMgAlO catalysts, with an average Ni particle size of ca. 5.4 nm. The presence of Cu species created CuNi alloy sites and Lewis acid-base pairs, and increased hydrogen transfer and condensation reactions, resulting in elevated etha- nol conversion and n-butanol selectivity. Additionally, CuNi alloy had a strong interaction with CuNiMgAl oxides, forming homogeneous boundary due to their close ionic radius and lattice matching, and afforded the long time stability in the ethanol to n-butanol reaction.

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Analysis of 3.4 Ah lithium-sulfur pouch cells by electrochemical impedance spectroscopy Dominika Capkova, Vaclav Knap, Andrea Strakova Fedorkova, Daniel-Ioan Stroe 2022, 72(9): 318-325.  DOI: 10.1016/j.jechem.2022.05.026 Abstract ( 13 )   PDF (2947KB) ( 3 )   Despite great progress in lithium-sulfur (Li-S) batteries, the electrochemical reactions in the cell are not yet fully understood. Electrode processes, complex interfaces and internal resistance may be character-ized by electrochemical impedance spectroscopy (EIS). EIS is a non-destructive technique and easy to apply, though there are challenges in ensuring the reproducibility of measurements and the interpreta-tion of impedance data. Here, we present the impedance behavior of a 3.4 Ah Li-S pouch cell character-ized by EIS. The impedance changes were analyzed over the entire depth-of-discharge, depth-of-charge, and at various temperatures. Based on the formation of intermediates during (dis)charging, the changes of resistances are observed. Overall, the increase in temperature causes a decrease in electrolyte viscosity, lowering the surface energy which can improve the penetration of the electrolyte into the electrode pores. Moreover, the effect of superimposed AC current during EIS measurement was analyzed, and the results show the dependence of the charge transfer resistance on superimposed AC current which was lower compared to steady-state conditions and consents with theory.

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Tip-induced directional charge separation on one-dimensional BiVO4 nanocones for asymmetric light absorption Nengcong Yang, Ruotian Chen, Chenwei Ni, Dongfeng Li, Qi Sun, Lifang Liu, Yu Qi, Shengye Jin, Xiuli Wang,fengtao Fan, Can Li, Fuxiang Zhang 2022, 72(9): 326-332.  DOI: 10.1016/j.jechem.2022.04.015 Abstract ( 9 )   PDF (6049KB) ( 5 )   One dimensional (1D) semiconductor is a class of extensively attractive materials for many emerging solar energy conversion technologies. However, it is still of shortage to assess the impact of 1D structural symmetry on spatial charge separation and understand its underlying mechanism. Here we take controllably-synthesized 1D BiVO4 nanocones and nanorods as prototypes to study the influence of 1D symmetry on charge separation. It is found that the asymmetric BiVO4 nanocones enable more effective charge separation compared with the symmetric nanorods. The unexpected spatial charge separation on the nanocones is mainly ascribed to uneven light absorption induced diffusion-controllable charge sep-aration due to symmetry breaking of 1D nanostructure, as evidenced by spatial and temporal resolved spectroscopy. Moreover, the promotion effect of charge separation on the nanocones was quantitatively evaluated to be over 20 times higher than that in BiVO4 nanorods. This work gives the first demonstration of the influence of 1D structural symmetry on the charge separation behavior, providing new insights to design and fabricate semiconductor materials for efficient solar energy conversion.

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Nonlinear health evaluation for lithium-ion battery within full-lifespan Heze You, Jiangong Zhu, Xueyuan Wang, Bo Jiang, Hao Sun, Xinhua Liu, Xuezhe Wei, Guangshuai Han, Shicong Ding, Hanqing Yu, Weihan Li, Dirk Uwe Sauer, Haifeng Dai 2022, 72(9): 333-341.  DOI: 10.1016/j.jechem.2022.04.013 Abstract ( 22 )   PDF (8203KB) ( 7 )   Lithium-ion batteries (LIBs), as the first choice for green batteries, have been widely used in energy stor-age, electric vehicles, 3C devices, and other related fields, and will have greater application prospects in the future. However, one of the obstacles hindering the future development of battery technology is how to accurately evaluate and monitor battery health, which affects the entire lifespan of battery use. It is not enough to assess battery health comprehensively through the state of health (SoH) alone, especially when nonlinear aging occurs in onboard applications. Here, for the first time, we propose a brand-new health evaluation indicator—state of nonlinear aging (SoNA) to explain the nonlinear aging phenomenon that occurs during the battery use, and also design a knee-point identification method and two SoNA quanti- tative methods. We apply our health evaluation indicator to build a complete LIB full-lifespan grading evaluation system and a ground-to-cloud service framework, which integrates multi-scenario data col- lection, multi-dimensional data-based grading evaluation, and cloud management functions. Our works fill the gap in the LIBs’ health evaluation of nonlinear aging, which is of great significance for the health and safety evaluation of LIBs in the field of echelon utilization such as vehicles and energy storage. In addition, this comprehensive evaluation system and service framework are expected to be extended to other battery material systems other than LIBs, yet guiding the design of new energy ecosystem.

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High entropy fluorides as conversion cathodes with tailorable electrochemical performance Yanyan Cui, Parvathy Anitha Sukkurji, Kai Wang, Raheleh Azmi, Alexandra M. Nunn, Horst Hahn, Ben Breitung, Yin-Ying Ting, Piotr M. Kowalski, Payam Kaghazchi, Qingsong Wang, Simon Schweidler, Miriam Botros 2022, 72(9): 342-351.  DOI: 10.1016/j.jechem.2022.05.032 Abstract ( 18 )   PDF (6536KB) ( 13 )   With the recent development of high entropy materials, an alternative approach to develop advanced functional materials with distinctive properties that show improved values compared to conventional materials has been provided. The high entropy concept was later successfully transferred to metal fluo-rides and high entropy fluorides (HEFs) were successfully synthesized. Owing to their high theoretical specific capacities in energy storage applications, HEFs were utilized as cathode materials for lithium-ion batteries (LIBs) and their underlying storage mechanisms were investigated. Instead of a step-by-step reduction of each individual metal cation, the HEFs seem to exhibit a single-step reduction process, indicating a solid solution compound instead of merely a mixture of different metal fluorides. It was also observed that the electrochemical behavior of the HEFs depends on each individual incorporated ele-ment. Therefore, by altering the elemental composition, new materials that exhibit improved electro-chemical properties can be designed. Remarkably, HEFs with seven incorporated metal elements exhibited a better cycling stability as well as a lower hysteresis compared to binary metal fluorides. These findings offer new guidelines for material design and tailoring towards high performance LIBs.

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High-performance magnesium ion asymmetric Ppy@FeOOH//Mn3O4 micro-supercapacitor Xueliang Lv, Yaxiong Zhang, Xijuan Li, Zhiye Fan, Guo Liu, Wenjian Zhang, Jinyuan Zhou, Erqing Xie, Zhenxing Zhang 2022, 72(9): 352-360.  DOI: 10.1016/j.jechem.2022.03.014 Abstract ( 5 )   PDF (9654KB) ( 1 )   Micro-supercapacitors (MSCs) are attractive electrochemical energy storage devices owing to their high power density and extended cycling stability. However, relatively low areal energy density still hinders their practical applications. Here, an asymmetric Mg ion MSC with promising high energy density is fab-ricated. Firstly, indium tin oxide (ITO) NWs were synthesized by chemical vapor deposition as the excel- lent current collector. Subsequently, nanostructured Mn3O4 and Ppy@FeOOH were deposited on the laser-engraved interdigital structure ITO NWs electrodes as the positive and negative electrodes, respec- tively. Beneficial from the hierarchical micro-nano structures of active materials, high conductive elec- tron transport pathways, and charge-balanced asymmetric electrodes, the obtained MSC possesses a high potential window of 2.2 V and a high areal capacitance of 107.3 mF cm-2 at 0.2 mA cm-2. The in-situ XRD, VSM, and ex-situ XPS results reveal that the primary energy storage mechanism of Mg ions in negative FeOOH electrode is Mg ions de-/intercalation and phase transition reaction of FeOOH. Furthermore, the MSC exhibits a high specific energy density of 71.18 lWh cm-2 at a power density of 0.22 mWh cm-2 and capacitance retention of 85% after 5000 cycles with unvaried Coulombic efficiency. These results suggest promising applications of our MSC in miniaturized energy storage devices.

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Anionic formulation of electrolyte additive towards stable electrocatalytic oxygen evolution in seawater splitting Meng Yu, Jinhan Li, Fangming Liu, Jiuding Liu, Wence Xu, Honglu Hu, Xijie Chen, Weichao Wang, Fangyi Cheng 2022, 72(9): 361-369.  DOI: 10.1016/j.jechem.2022.04.004 Abstract ( 15 )   PDF (9144KB) ( 24 )   Hydrogen generation through seawater electrolysis provides a promising, attractive pathway towards the utilization of sustainable energy. However, the catalytic activity and stability of oxygen evolution anode are severely limited by the chloride-induced corrosion and competitive oxidation reactions. In this work, we demonstrate an anion-assisted performance improvement strategy by quick and universal screening of electrolyte additive via correlating Cl- repellency with the anionic properties. Particularly, the addition of phosphate ions is found to enable highly stable alkaline seawater splitting at industry-level current density (0.5 A cm-2) over 500 h using transition metal hydroxides as anodic electrocatalysts. In situ experiments and theoretical simulations further reveal that the dynamic anti-corrosion behaviors of surface-adsorbed phosphate ions are attributed to three factors including repelling Cl- ions without sig-nificantly blocking OH- diffusion, preventing transition metal dissolution and acting as a local pH buffer to compensate the fast OH- consumption under high current electrolysis.

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High area-capacity Mg batteries enabled by sulfur/copper integrated cathode design Zhenfang Zhou, Aobing Du, Weijie Kong, Zhuang Chen, Zhonghua Zhang, Bingbing Chen, Yitao He, Shanmu Dong, Zhenjiang Li, Guicun Li, Guanglei Cui 2022, 72(9): 370-378.  DOI: 10.1016/j.jechem.2022.05.046 Abstract ( 7 )   PDF (9259KB) ( 6 )   Rechargeable Mg batteries potentially display lower cost and competitive energy density compared with their Li-ion counterparts. However, the practical implementation of high area-capacity cathodes still remains a formidably challenging task. This work presents the sulfur/copper integrated cathodes fabri- cated by the conventional blade-coating process and slurry-dipping method. The sulfur/copper foil inte- grated cathodes deliver a high area-capacity of 2.6 mAh cm-2 after 40 cycles, while the sulfur/copper-foam integrated cathode exhibits an ultrahigh area-capacity of 35.4 mAh cm-2, corresponding to 743.1 Wh L-1 at the electrode level (1.5 times higher than the LiCoO2-graphite system). The in-situ formed cop- per sulfide intermediates with sufficient cation defects can act as functional intermediates to regulate the sulfur electrochemistry during the first discharge process. The subsequent cycles are operated by the reversible displacement reaction between Mg-ions and copper sulfide active substances. In particular, the copper ions prefer to extrude along the [001] direction in copper sulfides lattice and simultaneously the rock-salt MgS crystals are generated. Besides, the nonuniform surface topography of the cycled Mg-metal anode, caused by the spatial inhomogeneity in current distribution, is demonstrated to lead to the battery performance degradation for high area-capacity Mg batteries.

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Mitigating the Jahn-Teller distortion driven by the spin-orbit coupling of lithium manganate cathode Shu Zhang, Hongyi Chen, Jun Chen, Shouyi Yin, Yu Mei, Lianshan Ni, Andi Di, Wentao Deng, Guoqiang Zou, Hongshuai Hou, Xiaobo Ji 2022, 72(9): 379-387.  DOI: 10.1016/j.jechem.2022.05.027 Abstract ( 12 )   PDF (6148KB) ( 21 )   Spinel LiMn2O4 is recognized as one of the most competitive cathode candidates for lithium-ion batteries ascribed to environmentally benign and rich sources. However, the wholesale application of LiMn2O4 is predominately plagued by its severe capacity degradation, mainly associated with the innate Jahn-Teller effect. Herein, single-crystalline LiMn2O4 with Eu3+ doping is rationally designed to mitigate the detri- mental Jahn-Teller distortion by tuning the chemical environment of MnO6 octahedra and accommodat-ing localized electron, based on the unique aspheric flexible 4f electron orbit of rare-earth metal ions. Notably, the stretching of MnO6 octahedron stemmed from the Jahn-Teller effect in Eu-doped LiMn2O4 is effectively suppressed, confirmed by theoretical calculation. Meanwhile, the structural stability of the material has been significantly enhanced due to the robust Mn-O band coherency and weakened phase transition, proved by synchrotron radiation absorption spectrum and operando X-ray diffraction. The corresponding active cathode manifests superior long-cycle stability after 300 loops at 2C and dis- plays only a 0.011% capacity drop per cycle even at 5C. Given this, this modification tactic sheds new light on achieving superior long-cycle performances by suppressing distortion in various cathode materials.

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Design of ultranarrow-bandgap acceptors for efficient organic photovoltaic cells and highly sensitive organic photodetectors Ye Xu, Tao Zhang, Huifeng Yao, Jingwen Wang, Pengqing Bi, Jianhui Hou 2022, 72(9): 388-394.  DOI: 10.1016/j.jechem.2022.05.038 Abstract ( 9 )   PDF (4339KB) ( 4 )   The fabrication of multifunctional electronic devices based on the intriguing natures of organic semicon-ductors is crucial for organic electronics. Ultranarrow-bandgap materials are in urgent demand for fab-ricating high-performance organic photovoltaic (OPV) cells and highly sensitive near-infrared organic photodetectors (OPDs). By combining alkoxy modification and an asymmetric strategy, three narrow-bandgap electronic acceptors (BTP-4F, DO-4F, and QO-4F) were synthesized with finely tuned molecular electrostatic potential (ESP) distributions. Through the careful modulation of electronic configurations, the optical absorption onsets of DO-4F and QO-4F exceeded 1 lm. The experimental and theoretical results suggest that the small ESP of QO-4F is beneficial for achieving a low nonradiative voltage loss, while the large ESP of BTP-4F can help obtain high exciton dissociation efficiency. By contrast, the asym-metric acceptor DO-4F with a moderate ESP possesses balanced voltage loss and exciton dissociation, yielding the best power conversion efficiency of 13.6% in the OPV cells. OPDs were also fabricated based on the combination of PBDB-T:DO-4F, and the as-fabricated device outputs a high shot-noise-limited specific detectivity of 3.05 - 1013 Jones at 850 nm, which is a very good result for near-infrared OPDs. This work is anticipated to provide a rational way of designing high-performance ultranarrow-bandgap organic semiconductors by modulating the molecular ESP.

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Delicate surface vacancies engineering of Ru doped MOF-derived Ni-NiO@C hollow microsphere superstructure to achieve outstanding hydrogen oxidation performance Yuting Yang, Yi Huang, Shuqing Zhou, Yi Liu, Luyan Shi, Tayirjan Taylor Isimjan, Xiulin Yang 2022, 72(9): 395-404.  DOI: 10.1016/j.jechem.2022.06.011 Abstract ( 8 )   PDF (6075KB) ( 3 )   Surface vacancy defects, as the bridge between theoretical structural study and the design of heteroge-nous catalysts, have captured much attention. This work develops a metal-organic framework-engaged replacement-pyrolysis approach to obtain highly dispersed Ru nanoparticles immobilized on the vacancy-rich Ni-NiO@C hollow microsphere (Ru/Ni-NiO@C). Fine annealing at 400 °C introduces nickel and oxygen vacancies on Ru/Ni-NiO@C surface, resulting in an improved electrical conductivity and rapid mass-charge transfer efficiency. Ru/Ni-NiO@C with a hollow micro/nanostructure and interconnected meso-porosity favors the maximal exposure of abundant active sites and elevation of hydrogen oxidation reaction (HOR) activity. Experimental results and density functional theory (DFT) calculations reveal that an electronic effect between Ru and Ni-NiO@C, in conjunction with nickel/oxygen vacancies in the NiO species could synergistically optimize hydrogen binding energy (HBE) and hydroxide binding energy (OHBE). The HBE and OHBE optimizations thus created confer Ru/Ni-NiO@C with a mass activity over 7.75 times higher than commercial Pt/C. Our work may provide a constructive route to make a break-through in elevating the hydrogen electrocatalytic performance.

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Design and performance improvement of SiNPs@graphene@C composite with a popcorn structure Hong Dong, Feifei Zong, Jie Wang, Hao Ding, Peng Wang, Ru Song, Ningshuang Zhang, Xuchun Cui, Shiyou Li 2022, 72(9): 405-415.  DOI: 10.1016/j.jechem.2022.05.031 Abstract ( 8 )   PDF (12586KB) ( 2 )   Silicon anodes are considered to be the most promising alternatives owing to their theoretical specific capacity, which is almost 10 times higher than that of graphite anodes. However, huge volume changes during charging and discharging affect their interface stability, which strongly limits their application in commercial batteries. Herein, a popcorn-structured silicon-carbon composite (SiNPs@graphene@C), com- posed of silicon nanoparticles (SiNPs), graphene spheres and pitch-based carbon, is prepared by spray- drying followed by a wet process. The resulting SiNPs@graphene@C composite has good flexibility and elastic-strain capacity due to the graphene substrate, and it possesses macrostructural integrity and mechanical stability during cycling due to the rigid carbon-carbon chemical bonds. As a result, it shows a discharge-specific capacity of 481.3 mAh g-1 and a capacity retention of 82.9% after 500 cycles at 1 A g-1. Besides, the initial coulomb efficiency is increased from 65.7% to 86.5% by pre-lithiation, which improves the feasibility of commercialising the SiNPs@graphene@C composite.

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3D hierarchical oxygen-deficient AlCoNi-(oxy)hydroxides/N-doped carbon hybrids enable efficient battery-type asymmetric supercapacitor Renjie Zhang, Wei Zhang, Qun Yang, Jidong Dong, Lina Ma, Zaixing Jiang, Yudong Huang 2022, 72(9): 416-423.  DOI: 10.1016/j.jechem.2022.04.050 Abstract ( 7 )   PDF (10088KB) ( 1 )   Polynary transition-metal layered hydroxides are promising energy materials owing to their unique architecture, impressive theoretical capacities, and adjustable compositions. Regulating the dimensional morphology and active sites/redox states are the keys to electrochemical performance enhancement. Distinguish from the reported mono-metal or binary-metal configurations, a new ternary-metal AlCoNi-LTH is coanchored onto a highly graphitized porous N-doped carbon matrix to develop superior 3D hierarchical microporous functional energy hybrids AlCoNi-LTHs/NAC. The constructed hybrids pos- sess superior structural durability, good electrical conductivity, and rich active sites due to the strong interfacial conjunction and favorable synergistic effect between the doped porous carbon and AlCoNi nanosheets. Consequently, the AlCoNi-LTHs/NAC hybrids demonstrate high conductivity, reasonable specific surface area, and superior specific capacitance, and the assembled hybrid battery-type superca- pacitor reveals an ideal energy density of 72.6 Wh kg-1 at a power density of 625 W kg-1, which is supe-rior to the reported devices. This strategy opens a platform to rationally design polynary transition-metal layered hydroxides and their hybrids for efficient supercapacitors.

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Bifunctional Mn-doped CoSe2 nanonetworks electrode for hybrid alkali/acid electrolytic H2 generation and glycerol upgrading Linfeng Fan, Yaxin Ji, Genxiang Wang, Zhifang Zhang, Luocai Yi, Kai Chen, Xi Liu, Zhenhai Wen 2022, 72(9): 424-431.  DOI: 10.1016/j.jechem.2022.04.027 Abstract ( 11 )   PDF (5081KB) ( 3 )   Electrolytic water splitting, as a promising route to hydrogen (H2) production, is still confronted with the sluggish anodic oxygen evolution reaction (OER) and its less value-added O2 production. Herein, we report a bifunctional electrode fabricated by in situ growth of Mn-doped CoSe2 nanonetworks on carbon fiber cloth (Mn-CoSe2/CFC), which shows attractive electrocatalytic properties toward glycerol oxidation reaction (GOR) in alkali and hydrogen evolution reaction (HER) in acid. A flow alkali/acid hybrid elec- trolytic cell (fA/A-hEC) was then developed by coupling anodic GOR with cathodic HER with the Mn-CoSe2/CFC bifunctional electrode. Such fA/A-hEC enables a rather low voltage of 0.54 V to achieve 10 mA cm-2, and maintain long-term electrolysis stability over 300-h operation at 100 mA cm-2 with Faraday efficiencies of over 99% for H2 and 90% for formate production. The designed bifunctional elec- trode in such innovative fA/A-hEC device provides insightful guidance for coupling energy-efficient hydrogen production with biomass upgradation.

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Paired formate and H2 productions via efficient bifunctional Ni-Mo nitride nanowire electrocatalysts Xuan Liu, Zhongying Fang, Xue Teng, Yanli Niu, Shuaiqi Gong, Wei Chen, Thomas J. Meyer, Zuofeng Chen 2022, 72(9): 432-441.  DOI: 10.1016/j.jechem.2022.04.040 Abstract ( 13 )   PDF (11146KB) ( 1 )   Electrocatalytic water splitting provides a potentially sustainable approach for hydrogen production, but is typically restrained by kinetically slow anodic oxygen evolution reaction (OER) which is of lesser value. Here, free-standing, hetero-structured Ni3N-Ni0.2Mo0.8N nanowire arrays are prepared on carbon cloth (CC) electrodes for hydrogen evolution reaction (HER) and glycerol oxidation reaction (GOR) to formate with a remarkably high Faradaic efficiency of 96%. A two-electrode electrolyzer for GOR-assisted hydro- gen production operates with a current density of 10 mA cm-2 at an applied cell voltage of 1.40 V, 220 mV lower than for alkaline water splitting. In-situ Raman measurements identify Ni (III) as the active form of the catalyst for GOR rather than Ni (IV) and in-situ Fourier transform infrared (FTIR) spectroscopy mea-surements reveal pathways for GOR to formate. From density functional theory (DFT) calculations, the Ni3N-Ni0.2Mo0.8N heterostructure is beneficial for optimizing adsorption energies of reagents and inter- mediates and for promoting HER and GOR activities by charge redistribution across the heterointerface. The same electrode also catalyzes conversion of ethylene glycol from polyethylene terephthalate (PET) plastic hydrolysate into formate. The combined results show that electrolytic H2 and formate production from alkaline glycerol and ethylene glycol solutions provide a promising strategy as a cost-effective energy supply.

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An ultra-fast charging strategy for lithium-ion battery at low temperature without lithium plating Yudi Qin, Pengyu Zuo, Xiaoru Chen, Wenjing Yuan, Rong Huang, Xiaokan Yang, Jiuyu Du, Languang Lu, Xuebing Han, Minggao Ouyang 2022, 72(9): 442-452.  DOI: 10.1016/j.jechem.2022.05.010 Abstract ( 26 )   PDF (8674KB) ( 18 )   Conventional charging methods for lithium-ion battery (LIB) are challenged with vital problems at low temperatures: risk of lithium (Li) plating and low charging speed. This study proposes a fast-charging strategy without Li plating to achieve high-rate charging at low temperatures with bidirectional chargers. The strategy combines the pulsed-heating method and the optimal charging method via precise control of the battery states. A thermo-electric coupled model is developed based on the pseudo-two-dimensional (P2D) electrochemical model to derive charging performances. Two current maps of pulsed heating and charging are generated to realize real-time control. Therefore, our proposed strategy achieves a 3 C equivalent rate at 0 °C and 1.5 C at -10 °C without Li plating, which is 10-30 times faster than the traditional methods. The entropy method is employed to balance the charging speed and the energy effi-ciency, and the charging performance is further enhanced. For practical application, the power limitation of the charger is considered, and a 2.4 C equivalent rate is achieved at 0 °C with a 250 kW maximum power output. This novel strategy significantly expands LIB usage boundary, and increases charging speed and battery safety.

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Selenium vacancy-rich and heteroatom-doped CoSe/Mo2CTx MXene prepared using ionic liquid dopants for pH-universal hydrogen evolution and flexible supercapacitors Mingjie Yi, Shunyou Hu, Na Li, Hao Wang, Jiaheng Zhang 2022, 72(9): 453-464.  DOI: 10.1016/j.jechem.2022.05.040 Abstract ( 14 )   PDF (8766KB) ( 2 )   Vacancy engineering is a useful methodology in the development of catalysts and electrode materials. Herein, we report the introduction of Se-vacancy pairs in heteroatom-doped (N, B, and F) CoSe/Mo2CTx MXene (NBF-CoSe/Mo2CTx) to enhance the hydrogen evolution reaction (HER) and supercapacitor activ-ities via an ionic liquid-mediated method. Se vacancy pairs and heteroatom doping enable the realloca-tion of local electron states and add active sites, improving the electrochemical activity of NBF-CoSe/ Mo2CTx with high HER activities over a broad range of pH. At a current density of 10 mA cm-2, over-voltages of 70 and 81 mV are respectively produced in 0.5 M H2SO4 and 1 M KOH. The optimal structure also exhibits outstanding electrochemical performance in an asymmetric supercapacitor with an energy density of 34.2 Wh kg-1 at a power density of 15989.6 W kg-1. This study opens new avenues for the introduction of Se vacancies and heteroatom doping to improve the application performance.

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Suppressing byproduct formation for high selective CO2 reduction over optimized Ni/TiO2 based catalysts Danyang Li, Ruidong Xu, Roong Jien Wong, Xing Zhu, Dong Tian, Lei Jiang, Qingjie Guo, Hongcun Bai, Linan Huang, Wen Liu, Hua Wang, Kongzhai Li 2022, 72(9): 465-478.  DOI: 10.1016/j.jechem.2022.04.024 Abstract ( 13 )   PDF (4249KB) ( 2 )   One of the challenges for catalytic CO2 reduction is to control product selectivity, and new findings that can modify selectivity would be transformative. Herein, two kinds of TiO2 (homemade and commercial) with the same crystal phase but different surface properties are chosen as supports to prepare Ni-based catalysts for CO2 reduction, which show distinctly different product selectivity for CO2 reduction to CH4 or CO, as well as the CO2 conversion. The catalysts based on the homemade TiO2 support are highly selec-tive for CH4 formation, while the latter ones are about 100% selective for CO formation under the same reaction conditions. In addition, the former ones are much active (more than 3 times) than the latter ones. We found that the collaborative contribution of Ti3+ and Ni2+ species and the electronic metal-support interactions effect maybe the main driving force behind for determining the product selectivity. Methane is almost exclusively produced over the catalysts with abundant Ti3+ and Ni2+ species and greater electronic metal-support interaction, otherwise, it will give priority to CO generation. The addi-tion of CeO2 can reduce the Ni particle size and improve the dispersion of Ni nanoparticles, as well as cre- ate more Ti3+ species, contributing to the enhancement of CO2 conversion, but shows a negligible effect on product selectivity. Furthermore, the in situ DRIFT experiments and kinetic experiments indicate that the CO route is probably involved in the CO2 reduction process over the homemade Ni-CeO2/TiO2-CO cat-alyst with abundant Ti3+ and Ni2+ species and a strong electronic transform effect.

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Pumpkin-like MoP-MoS2@Aspergillus niger spore-derived N-doped carbon heterostructure for enhanced potassium storage Daoguang Sun, Cheng Tang, Hui Cheng, Weilan Xu, Aijun Du, Haijiao Zhang 2022, 72(9): 479-486.  DOI: 10.1016/j.jechem.2022.05.043 Abstract ( 9 )   PDF (6384KB) ( 4 )   Biomass-derived carbon materials are widely applied in the energy storage and conversion fields due to their rich sources, low price and environmental friendliness. Herein, a unique pumpkin-like MoP- MoS2@Aspergillus niger spore-derived N-doped carbon (SNC) composite has been prepared via a simple hydrothermal and subsequent phosphorization process. Interestingly, the resulting MoP-MoS2@SNC well inherits the pristine morphology of spore carbon, similar to the natural pumpkin, with hollow interiors and uneven protrusions on the surface. The special structure allows it to have sufficient space to fully contact the electrolyte and greatly reduces the ion transport distance. The theory calculations further demonstrate that the formed MoP-MoS2 heterostructure can enhance the adsorption of K ions and elec- tronic couplings. With these unique advantages, the MoP-MoS2@SNC anode for potassium storage shows a high reversible capability of 286.2 mAh g-1 at 100 mA g-1 after 100 cycles and superior rate perfor- mance. The enhanced electrochemical performance is mainly related to the unique pumpkin-like mor-phology of SNC and the construction of MoP-MoS2 heterostructure, as well as their perfect coupling. This study provides a feasible design idea for developing green, low-cost, and high-performance electrode materials for next-generation energy storage.

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Antioxidative solution processing yields exceptional Sn(II) stability for sub-1.4 eV bandgap inorganic perovskite solar cells Mingyu Hu, Gaopeng Wang, Qinghong Zhang, Jue Gong, Zhou Xing, Jinqiang Gao, Jian Wang, Peng Zeng, Shizhao Zheng, Mingzhen Liu, Yuanyuan Zhou, Shihe Yang 2022, 72(9): 487-494.  DOI: 10.1016/j.jechem.2022.05.030 Abstract ( 23 )   PDF (5305KB) ( 9 )   Owing to the combined features of sub-1.4 eV bandgap and all-inorganic composition, cesium tin-lead (Sn-Pb) triiodide perovskite is promising for approaching the Shockley-Queisser limit of solar cells while avoiding the use of volatile organic cations. But the low Sn(II) stability in this perovskite remains a hurdle for delivering its theoretically attainable device performance. Herein we present a synthesis method of this perovskite based on an acetylhydrazine-incorporated antioxidative solution system. Mechanistic investigation shows that acetylhydrazine effectively reduces the oxidation of solution-phase Sn(II) and meanwhile creates an electron-rich, protective nano-environment for solid-state Sn(II) ions. These lead to high oxidation resistance of the final film as well as effective defect inhibition. The resultant solar cells demonstrate power conversion efficiencies up to 15.04%, the highest reported so far for inorganic per- ovskite devices with sub-1.4 eV bandgaps. Furthermore, the T90 lifetime of these devices can exceed 1000 hours upon light soaking in a nitrogen atmosphere, demonstrating the potential advantage when lower-bandgap perovskite solar cells go all-inorganic.

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Modulation effects of Cu modification and ligands (oxalate and borohydride) functionalization on Pt d-band center, upper d-band edge, and alloyed PtCe support acidity on semihydrogenation of acetylene Olumide Bolarinwa Ayodele 2022, 72(9): 495-508.  DOI: 10.1016/j.jechem.2022.05.035 Abstract ( 9 )   PDF (6115KB) ( 2 )   The modulating effects of Cu modification and oxalate or borohydride ligands functionalization on the structure, catalyst d-band center (ed), upper d-band edge (eu), and acetylene partial hydrogenation of expediently synthesized Ce alloyed Pt supported catalysts were investigated. Firstly, a 5 wt% Pt alloyed Ce was synthesized via flame spray pyrolysis. The PtCe sample was further supported on zeolite Y, ZY, (PtCe/ZY) and copper modified ZY (PtCe/Cu-ZY). Furthermore, the PtCe was supported on two other oxa-late and borohydride ligands functionalized copper modified ZY (PtCe/CuX-ZY and PtCe/CuB-ZY, respec-tively). The high-angle annular darkfield scanning transmission electron microscopy (HAADF/STEM) data showed a reduction in the PtO average particle size from 2.65 nm in PtCeO2 to average 1.73, 0.64, and 0.30 nm in PtCe/Cu-ZY, PtCe/CuX-ZY, and PtCe/CuB-ZY, which was corroborated by the electron energy-loss spectroscopy (EELS) results wherein nonhomogeneous mixing of elements was seen with segregated Pt clusters in the non-functionalized samples. Conversely, both PtCe/CuX-ZY and PtCe/CuB-ZY samples showed near-perfect homogeneity with no distinct Pt signals. The measured eu values for PtCe, PtCe/Cu-ZY, PtCe/CuX-ZY, and PtCe/CuB-ZY are +1.85, +0.40, -0.15, and -0.19 eV, respectively. The positive values indicated strong metal-adsorbate bonding typical of large Pt sizes while the negative values indicated weak metal-adsorbate bonding due to highly downsized Pt sizes. The ethylene yield (YC2H4) over the PtCe sample showed depletion as the reaction temperature increased, while it reflected maxima at 120 °C with 55.3% YC2H4 over PtCe/ZY. The maxima shifted to 180 °C with enhanced YC2H4 of 71.4% in PtCe/Cu-ZY. On the contrary, both PtCe/CuX-ZY and PtCe/CuB-ZY exhibited a monotonous increase in YC2H4 up to the maximum C2H2 conversion with YC2H4 of 81.9% and 92.1% at 180 and 160 °C, respectively. These results showed that both the Cu modification and ligands functionalization were highly invaluable to enhance the properties and activities of the semihydrogenation of acetylene (SHA) catalysts.

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The surface of metal boride tinted by oxygen evolution reaction for enhanced water electrolysis Xu Zou, Wei Zhang, Xinyan Zhou, Kexin Song, Xin Ge, Weitao Zheng 2022, 72(9): 509-515.  DOI: 10.1016/j.jechem.2022.05.039 Abstract ( 8 )   PDF (4168KB) ( 4 )   Oxygen evolution reaction (OER) is a bottleneck half-reaction in many important energy conversion pro-cesses (e.g., water splitting), and one of the key issues lies to develop high-efficiency, cost-effective OER electrocatalysts. Rather than those popular extrinsic modulations of any catalysts with gradually degraded performance, we aim at the utilization of the intermediates offered from the undergoing OER as long-standing electrocatalysts. Herein, by inverted design, we extracted the bimetallic borides (FeCoB2)-derived intermediates metal borates in the OER, unlocking their potential as a self- functionalized highly active catalytic phase in-situ formed on the metal boride surface for continuing OER operation. Mechanistically, the surface metal atoms are oxidized to oxyhydroxides, and the surface metalloids (B) are further transformed to the corresponding oxoanions to form metal borates. Such OER self-produced electrocatalyst exhibits a small overpotential of 295 mV at 10 mA/cm2 and its high cat-alytic activity lasts even after 200 h. Compared with FeCoB2, the catalytic activity of this electrochemi-cally activated FeCoB2 is -7 times higher. The in-situ formed metal borate is dominatingly responsible for the obtained high catalytic activity. Such unique OER-produced self-functionalization surfaces of metal borates afford to greatly reduce the energy barrier of the continuing OER, thereby accelerating the reaction process.

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Construction of monodispersed single-crystalline hierarchical ZSM-5 nanosheets via anisotropic etching Tianli Zhou, Dazhi Zhang, Yi Liu, Yanwei Sun, Taotao Ji, Shengjun Huang, Yi Liu 2022, 72(9): 516-521.  DOI: 10.1016/j.jechem.2022.06.008 Abstract ( 14 )   PDF (4304KB) ( 6 )   Hierarchical zeolites and single-crystalline zeolite nanosheets (NSs) have been recognized as two sepa-rate types of targeting porous materials to overcome the diffusion limitations of traditional bulk zeolites. The synthesis of uniform single-crystalline hierarchical zeolite NSs featured with NS morphology and interconnected mesoporosity, remains rarely reported. In this work, we prepared ZSM-5 zeolites with the above microstructural features via simple alkaline etching. Moreover, both their microstructure and acid strength could be accurately tuned with this approach, resulting in not only higher conversion rate and BTX selectivity but also superior anti-coking performance in the subsequent methanol aromati-zation reaction.

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A self-healing liquid metal anode for lithium-ion batteries Yaqin Qi, Chao Shen, Qian Hou, Zengying Ren, Ting Jin, Keyu Xie 2022, 72(9): 522-531.  DOI: 10.1016/j.jechem.2022.05.018 Abstract ( 18 )   PDF (5876KB) ( 10 )   The gallium-based liquid metal as one of the self-healing materials has gained wide attention, especially in the energy storage system. However, volume expansion with the ‘‘liquid-solid-liquid” transformation process still leads to un-controlled electrode failure, which stimulates the irreversibility of liquid metal and hinders their self-healing effect as the anode for lithium-ion batteries. Herein, the polypyrrole (PPy) with highly conductive and adhesive features is first introduced to fasten the liquid metal nanopar- ticles (gallium-tin alloy, EGaSn) in the integrated electrode and applied as the anode for lithium-ion bat- teries. A tightly PPy wrapped EGaSn nanoparticles structure is formed during the in-situ polymerization synthesis process, which effectively avoids the detachment of solid alloyed products. Based on the fea- tures of PPy, polyacrylic acid is added to facilitate strengthening the integrity of the electrode by con- structing the hydrogen bond. The ‘‘dual-insurance” design endows the EGaSn to exhibit superior electrochemical kinetics and an astonishing self-healing effect. As a result, the customized anode displays superior cycling stability (499.8 mAh g-1 after 500 cycles at 1.0 A g-1) and rate capability (350 mAh g-1 at 2.0 A g-1). This work enriches the electrode engineering technology of liquid metal nanoparticles and opens up a new way to customize the self-healing anode for lithium-ion batteries.

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Closed-loop cobalt recycling from spent lithium-ion batteries based on a deep eutectic solvent (DES) with easy solvent recovery Taibai Li, Yige Xiong, Xiaohui Yan, Tao Hu, Siqi Jing, Zhongjie Wang, Xiang Ge 2022, 72(9): 532-538.  DOI: 10.1016/j.jechem.2022.05.008 Abstract ( 25 )   PDF (4388KB) ( 8 )   Efficient recycling technology for the rapid growth of spent lithium-ion batteries (LIBs) is essential to tackle the resources and environmental crisis. Hydrometallurgical approach has attracted extensive research due to its potential to reduce the consumption of energy and threat to the environment. However, the simultaneous realization of green, efficient and closed-loop recycling is still challenging. Herein, we report a closed-loop and highly efficient approach to recycle lithium cobalt oxide from spent LIBs based on a choline chloride:oxalic acid (ChCl:OA) type deep eutectic solvent (DES). An ultrafast leaching process is observed at 180 °C for 10 s with no observable residues. The energy barrier during leaching is calculated to be 113.9 kJ/mol. Noteworthy, the solubility of cobalt ions can be reversibly tuned by simply adding/evaporating deionized water, thus avoiding the addition of precipitant and enabling the easy recovery of the leaching solvent for realizing a closed-loop recycling process. The simultaneous real-ization of high efficiency, green and closed-loop process is expected to push the DES into practical appli-cation for recycling the electrodes of LIBs.

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Cs-content-dependent organic cation exchange in FA1-xCsxPbI3 perovskite Meng Ren, Jielin Shi, Yuetian Chen, Yanfeng Miao*, Yixin Zhao 2022, 72(9): 539-544.  DOI: 10.1016/j.jechem.2022.05.042 Abstract ( 21 )   PDF (4192KB) ( 6 )   FA-Cs mixed-cation perovskite has been reported as a promising candidate for obtaining highly efficient and stable photovoltaic devices. Phenylethylamine iodide (PEAI) post-treatment is a widely used and effective method for surface passivation of FA-Cs perovskite layer in devices. However, it is still contro- versial whether the PEAI post-treatment would form two-dimensional (2D) perovskite PEA2PbI4 capping layer or just result in PEA+ terminated surface. Here in this work, the function of PEAI post-treatment on FA-Cs mixed-cation perovskite FA1-xCsxPbI3 (x = 0.1-0.9) with varied Cs contents is elucidated. With increased Cs content, the FA-Cs perovskite shows higher resistance to the cation exchange between FA+ and PEA+. This Cs-content-dependent cation exchange results in the different PEAI reaction prefer-ences with FA-Cs mixed-cation perovskites. Furthermore, higher Cs content with stronger resistance to cation exchange reaction leads to a wider processing window for post-treatment and defect passivation, which is beneficial for the fabrication of large-scale photovoltaic devices.

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ZIF-derived holey electrode with enhanced mass transfer and N-rich catalytic sites for high-power and long-life vanadium flow batteries Yongbin Liu, Lihong Yu, Xin Liu, Le Liu, Jingyu Xi 2022, 72(9): 545-553.  DOI: 10.1016/j.jechem.2022.06.004 Abstract ( 17 )   PDF (7047KB) ( 7 )   Electrode materials with good redox kinetics, excellent mass transfer characteristics and ultra-high sta- bility play a crucial role in reducing the life-cycle cost and prolonging the maintenance-free time of the vanadium flow batteries (VFB). Herein, a nitrogen-doped porous graphite felt electrode (N-PGF) is pro- posed by growing ZIF-67 nanoparticles on carbon fibers and then calcinating and acid etching. The multi-scale structure of "carbon fiber gap (electrolyte flow), micro/nano pore (active species diffusion) and Nitrogen active center (reaction site)" in N-PGF electrode effectively increases the catalytic sites and promotes mass transfer characteristics. Reasonable electrode design makes the battery show excel- lent rate performance and ultra-high cycling stability. The peak power density of the battery reaches 1006 mW cm-2. During 1000 cycles at 150 mA cm-2, the average discharge capacity and average dis- charge energy of N-PGF increase substantially by 11.6% and 23.4% compared with the benchmark thermal activated graphite felt, respectively. More excitingly, after ultra-long term (5000 cycles) operation at an ultra-high current density (300 mA cm-2), N-PGF exhibits an unprecedented energy efficiency retention (99.79%) and electrochemical performance stability.

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Molecular-scale controllable conversion of biopolymers into hard carbons towards lithium and sodium ion batteries: A review Li-Jing Xie, Cheng Tang, Ming-Xin Song, Xiao-Qian Guo, Xiao-Ming Li, Jing-Xue Li, Chong Yan, Qing-Qiang Kong, Guo-Hua Sun, Qiang Zhang, Fang-Yuan Su, Cheng-Meng Chen 2022, 72(9): 554-569.  DOI: 10.1016/j.jechem.2022.05.006 Abstract ( 93 )   PDF (14178KB) ( 71 )   Hard carbons are widely investigated as potential anodes for lithium and sodium ion batteries owing to their internally well-tailored textures (closed pores and defects) and large microcrystalline interlayer spacing. The renewable biomass is a green and economically attractive carbon source to produce hard carbons. However, the chemical and structural complexity of biomass has plagued the understanding of evolution mechanism from organic precursors to hard carbons and the structure-property relationship. This makes it difficult to finely tune the microstructure of biomass-derived hard carbons, thus greatly restricting their high-performance applications. Most recently, the optimal utilization and controllable conversion of biomass-derived biopolymers (such as starch, cellulose and lignin) at the molecular level have become a burgeoning area of research to develop hard carbons for advanced batteries. Considering the principal source of carbonaceous materials is from biomass pyrolysis, we firstly overview the chemical structures and pyrolysis behaviors of three main biopolymers. Then, the controllable prepa-ration of hard carbons using various physicochemical properties of biopolymers at the molecular level is systematically discussed. Furthermore, we highlight present challenges and further opportunities in this field. The Review will guide future research works on the design of sustainable hard carbons and the opti-mization of battery performance.

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A novelty strategy induced pinning effect and defect structure in Ni-rich layered cathodes towards boosting its electrochemical performance Zhouliang Tan, Yunjiao Li, Xiaoming Xi, Shijie Jiang, Xiaohui Li, Xingjie Shen, Panpan Zhang, Zhenjiang He, Junchao Zheng 2022, 72(9): 570-580.  DOI: 10.1016/j.jechem.2022.05.037 Abstract ( 24 )   PDF (19342KB) ( 22 )   Layered Ni-rich transition metal oxide is treated as the most promising alternative cathode due to their high-capacity and flexible composition. However, the severe lattice strain and slow Li-ion migration kinet-ics severely restrict their practical application. Herein, a novelty strategy induced pinning effect and defect structure in layered Ni-rich transition metal oxide cathodes is proposed via a facile cation(iron ion)/anion (polyanion) co-doping method. Subsequently, the effects of pinning effect and defect structure on element valence state, crystal structure, morphology, lattice strain, and electrochemical performance during lithi-ation/delithiation are systematically explored. The detailed characterizations (soft X-ray absorption spec-troscopy (sXAS), in-situ X-ray diffraction (XRD), etc.) and density functional theory (DFT) calculation demonstrate that the pinning effects built-in LiNi0.9Co0.05Mn0.05O2 materials by the dual-site occupation of iron ions on lithium and transition metal sites effectively alleviate the abrupt lattice strain caused by an unfavorable phase transition and the subsequent induction of defect structures in the Li layer can greatly reduce the lithium-ion diffusion barrier. Therefore, the modified LiNi0.9Co0.05Mn0.05O2 exhibits a high-capacity of 206.5 mAh g-1 and remarkably enhanced capacity retention of 93.9% after 100 cycles, far superior to -14.1% of the pristine cathodes. Besides, an excellent discharge capacity of 180.1 mAh g-1 at 10 C rate is maintained, illustrating its remarkable rate capability. This work reports a pinning effect and defect engineering method to suppress the lattice strain and alleviate lithium-ion kinetic barriers in the Ni-rich layered cathodes, providing a roadmap for understanding the fundamental mechanism of an intrinsic activity modulation and structural design of layered cathode materials.