Journal of Energy Chemistry

Global instability index as a crystallographic stability descriptor of halide and chalcogenide perovskites Author links open overlay panel

Weiqiang Feng, Ruoting Zhao, Xiaoyu Wang, Bangyu Xing, Yilin Zhang, Xin He, Lijun Zhang

2022, 70(7): 1-8. DOI: 10.1016/j.jechem.2022.02.018

Abstract ( 25 )

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Crystallographic stability is an important factor that affects the stability of perovskites. The stability dictates the commercial applications of lead-based organometal halide perovskites. The tolerance factor (t) and octahedral factor (μ) form the state-of-the-art criteria used to evaluate the perovskite crystallographic stability. We studied the crystallographic stabilities of halide and chalcogenide perovskites by exploring an effective alternative descriptor, the global instability index (GII) that was used as an indicator of the stability of perovskite oxides. We particularly focused on determining crystallographic reliability by calculating GII. We analyzed the bond valence models of the 243 halide and chalcogenide perovskites that occupied the lowest-energy cubic-phase structures determined by conducting the first-principles-based total energy minimization calculations. The decomposition energy () reflects the thermodynamic stability of the system and is considered as the benchmark that helps assess the effectiveness of GII in evaluating the crystallographic stability of the systems under study. The results indicated that the accuracy of predicting thermodynamic stability was significantly higher when GII (73.6%) was analyzed compared to the cases when t (55%) and μ (39.1%) were analyzed to determine the stability. The results obtained from the machine learning-based data mining method further indicate that GII is an important descriptor of the stability of the perovskite family.

Gadolinium-incorporated CsPbI₂Br for boosting efficiency and long-term stability of all-inorganic perovskite solar cells Author links open overlay panel

Xingyu Pu, Jiabao Yang, Tong Wang, Shuaici Cheng, Qi Cao, Junsong Zhao, Hui Chen, Yixin Zhang, Tingting Xu, Ilhom Tojiboyev, Hadi Salari, Xuanhua Li

2022, 70(7): 9-17. DOI: 10.1016/j.jechem.2022.02.004

Abstract ( 17 )

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All-inorganic CsPbI₂Br perovskite solar cells (PSCs) have received extensive research interests recently. Nevertheless, their low efficiency and poor long-term stability are still obstacles for further commercial application. Herein, we demonstrate that high efficiency and exceptional long-term stability are realized by incorporating gadolinium(III) chloride (GdCl₃) into the CsPbI₂Br perovskite film. The incorporation of GdCl₃ enhances the Goldschmidt tolerance factor of CsPbI₂Br perovskite, yielding a dense perovskite film with small grains, thus the α-phase CsPbI₂Br is remarkably stabilized. Additionally, it is found that the GdCl₃-incorporated perovskite film achieves suppressed charge recombination and appropriate energy level alignment compared with the pristine CsPbI₂Br film. The noticeable increment in efficiency from 14.01% (control PSC) to 16.24% is achieved for GdCl₃-incorporated PSC. Moreover, the nonencapsulated GdCl₃-incorporated PSC exhibits excellent environmental and thermal stability, remaining over 91% or 90% of the original efficiency after 1200 h aging at 40% relative humidity or 480 h heating at 85 °C in nitrogen glove box respectively. The encapsulated GdCl₃-incorporated PSC presents an improved operational stability with over 88% of initial efficiency under maximum power point (MPP) tracking at 45 °C for 1000 h. This work presents an effective ion-incorporation approach for boosting efficiency and long-term stability of all-inorganic PSCs.

Conﬁned synthesis of MoS₂with rich co-doped edges for enhanced hydrogen evolution performance

Zongge Li, Chenlei Li, Jianwen Chen, Xu Xing, Yaqun Wang, Ying Zhang, Miaosen Yang, Guoxin Zhang

2022, 70(7): 18-26. DOI: 10.1016/j.jechem.2022.01.001

Abstract ( 19 )

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Activating MoS2 with atomic metal doping is promising to harvest desirable Pt-matched hydrogen evo-lution reaction (HER) catalytic performance. Herein, we developed an efﬁcient method to access edge- rich lattice-distorted MoS2 for highly efﬁcient HER via in-situ sulphuration of atomic Co/Mo species that were well-dispersed in a formamide-derived N-doped carbonaceous (f-NC) substrate. Apart from others, pre-embedding Co/Mo species in f-NC controls the release of metal sources upon annealing in S vapor, grafting the as-made MoS2 with merits of short-range crystallinity, distorted lattices, rich defects, and more edges exposed. The content of atomic Co species embedded in MoS2 reaches up to 2.85 at.%, and its atomic dispersion has been systematically conﬁrmed by using XRD, HRTEM, XPS, and XAS character-izations. The Co-doped MoS2 sample exhibits excellent HER activity, achieving overpotentials of 67 and 155 mV at j = 10 mA cm^-2 in 1.0 M KOH and 0.5 M H2SO4, respectively. Density functional theory sim- ulations suggest that, compared with free-doping MoS2, the edged Co doping is responsible for the sig- niﬁcantly improved HER activity. Our method, in addition to providing reliable Pt-matched HER catalysts, may also inspire the general synthesis of edge-rich metal-doped metal chalcogenide for a wide range of energy conversion applications.

In-situ doping-induced lattice strain of NiCoP/S nanocrystals for robust wide pH hydrogen evolution electrocatalysis and supercapacitor

Yan Lin, Xiaomeng Chen, Yongxiao Tuo, Yuan Pan, Jun Zhang

2022, 70(7): 27-35. DOI: 10.1016/j.jechem.2022.02.024

Abstract ( 17 )

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Developing high-efﬁciency multifunctional nanomaterials is promising for wide pH hydrogen evolution reaction (HER) and energy storage but still challenging. Herein, a novel in-situ doping-induced lattice strain strategy of NiCoP/S nanocrystals (NCs) was proposed through using seed crystal conversion approach with NiCo2S4 spinel as precursor. The small amount of S atoms in NiCoP/S NCs perturbed the local electronic structure, leading to the atomic position shift of the nearest neighbor in the protocell and the nanoscale lattice strain, which optimized the H* adsorption free energy and activated H2O mole-cules, resulting the dramatically elevated HER performance within a wide pH range. Especially, the NiCoP/S NCs displayed better HER electrocatalytic activity than comical 20% Pt/C at high current density in 1 M KOH and natural seawater: it only needed 266 mV vs. reversible hydrogen electrode (RHE) and 660 mV vs. RHE to arrive the current density of 350 mA cmÀ2 in 1 M KOH and natural seawater, indicating the application prospect for industrial high current. Besides, NiCoP/S NCs also displayed excellent super- capacitor performance: it showed high speciﬁc capacity of 2229.9 F gÀ1 at 1 A gÀ1 and energy density of 87.49 Wh kgÀ1, when assembled into an all-solid-state ﬂexible device, exceeding performance of most transition metal phosphides. This work provides new insights into the regulation in electronic structure and lattice strain for electrocatalytic and energy storage applications.

Elucidation of the sodiation/desodiation mechanism in Ca_0.5Ti₂(PO₄)₃/C as promising electrode for sodium batteries: New insights into the phase transitions

Abdelhaq Nassiri, Noha Sabi, Angelina Sarapulova, Yingjin Wei, Bouchaib Manoun, Sylvio Indris, Alexandr Missyul, Helmut Ehrenberg, Ismael Saadoune

2022, 70(7): 36-44. DOI: 10.1016/j.jechem.2022.01.036

Abstract ( 10 )

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The structure evolution and electrochemical performance of NaSICON-type Ca0.5Ti2(PO4)3 for sodium bat-teries are presented. This phosphate was synthesized by a solid-state method, and the obtained particles were coated with carbon using sucrose. This compound crystallizes in the rhombohedral system with space group R-3. The presence of carbon in the Ca0.5Ti2(PO4)3/C composite was conﬁrmed by Raman and Thermogravimetric analysis. The electrochemical performance of Ca0.5Ti2(PO4)3/C was investigated in the potential window 1.5-3.0 V vs. sodium metal at different scan rates. The compound is able to ini- tially intercalate/deintercalate 1.6/1.15 Na per formula unit, respectively. In operando synchrotron diffraction was done in the potential window 0.02-3.0 V vs. Na|Na+ and revealed the occurrence of sev- eral reaction regions upon ﬁrst discharge. Up to 4 Na+ ion per formula unit can be inserted during the ﬁrst discharge. An intensive reﬁnement of the synchrotron X-ray diffraction (SXRD) patterns of discharged NaxCa0.5Ti2(PO4)3 evidenced the existence of ﬁve regions depending on the sodium content while the crystal structures of new phases were elucidated for the ﬁrst time where sodium insertion occurs in the unusual M3 and M’ 3 sites of the NaSICON structure.

New insights for the catalytic oxidation of cyclohexane to K-A oil

Alessandro Vomeri, Marta Stucchi, Alberto Villa, Claudio Evangelisti, Andrea Beck, Laura Prati

2022, 70(7): 45-51. DOI: 10.1016/j.jechem.2022.02.008

Abstract ( 27 )

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Au-based catalysts have been reported to be active in the cyclohexane oxidation to K-A oil, but they showed some limitiations in terms of productivity, selectivity and required reaction conditions. The pos- sibility to overcome some of these limits has been explored coupling Au with Cu, which can be suitable for undergoing the electron-switch in the initial step of the cyclohexane oxidation. Hence, a bimetallic 2 wt% AuCu/Al2O3 catalyst was tested in the oxidation of cyclohexane, working at mild conditions of 120 °C and 4 bar of O2. The combination of the catalyst with a very small amount of benzaldehyde used as cheaper and non-toxic radical initiator allowed to obtain a very high productivity of cyclohexanol and cyclohexanone (45 mmol*mL/mgmet*h) with a selectivity of 94%. Moreover, comparing the catalyzed reaction with the non-catalysed one, the role of the catalyst has been disclosed.

Quench-tailored Al-doped V₂O₅nanomaterials for efﬁcient aqueous zinc-ion batteries

Hanmei Jiang, Wenbin Gong, Yifu Zhang, Xin Liu, Moaz Waqar, Jingjing Sun, Yanyan Liu, Xueying Dong, Changgong Meng, Zhenghui Pan, John Wang

2022, 70(7): 52-58. DOI: 10.1016/j.jechem.2022.02.030

Abstract ( 19 )

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Rechargeable aqueous zinc-ion batteries (ZIBs) are regarded as a promising competition to lithium-ion batteries as energy storage devices, owing to their high safety and low cost. However, the development of high-performance ZIBs is largely hindered by the shortage of ideal cathode materials with high-rate capability and long-cycle stability. Herein, we address this bottleneck issue by the quenching-tailored surface chemistry of V2O5 cathode nanomaterial. By rapid quenching from high temperatures, Al ions are doped into V2O5 lattice (Al-V2O5) and abundant oxygen vacancies are formed on the surface/near-surface, which facilitate the desired rapid electron transfers. Our density functional theory (DFT) simula- tions elucidate that the doping of Al ions into V2O5 remarkably reduces the Zn2+-diffusion barriers and improves the electrical conductivity of V2O5. As a proof-of-concept application, the thus-optimized Al- V2O5 cathode delivers a superior speciﬁc capacity of 532 mAh g^-11 at 0.1 A g^-1 and a long-cycling life with 76% capacity retention after 5000 cycles, as well as a good rate performance. This work provides not only a novel strategy for tuning the surface chemistry of V2O5 to boost the Zn2+ storage but also a general path- way of modifying metal oxides with improved electrochemical performance.

The chemical origin of temperature-dependent lithium-ion concerted diffusion in sulﬁde solid electrolyte Li₁₀GeP₂S₁₂

Zhong-Heng Fu, Xiang Chen, Nan Yao, Xin Shen, Xia-Xia Ma, Shuai Feng, Shuhao Wang, Rui Zhang, Linfeng Zhang, Qiang Zhang

2022, 70(7): 59-66. DOI: 10.1016/j.jechem.2022.01.018

Abstract ( 24 )

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Solid-state batteries have received increasing attention in scientiﬁc and industrial communities, which beneﬁts from the intrinsically safe solid electrolytes (SEs). Although much effort has been devoted to designing SEs with high ionic conductivities, it is extremely difﬁcult to fully understand the ionic diffu-sion mechanisms in SEs through conventional experimental and theoretical methods. Herein, the temperature-dependent concerted diffusion mechanism of ions in SEs is explored through machine- learning molecular dynamics, taking Li10GeP2S12 as a prototype. Weaker diffusion anisotropy, more dis- ordered Li distributions, and shorter residence time are observed at a higher temperature. Arrhenius-type temperature dependence is maintained within a wide temperature range, which is attributed to the lin-ear temperature dependence of jump frequencies of various concerted diffusion modes. These results provide a theoretical framework to understand the ionic diffusion mechanisms in SEs and deepen the understanding of the chemical origin of temperature-dependent concerted diffusions in SEs.

Ternary strategy: An analogue as third component reduces the energy loss and improves the efﬁciency of polymer solar cells

Longzhu Liu, Hanjian Lai, Feng He

2022, 70(7): 67-73. DOI: 10.1016/j.jechem.2022.02.025

Abstract ( 6 )

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Ternary strategy is a convenient and effective method to boost the performance of polymer solar cells (PSCs). Utilizing a ternary strategy to trade-off between the energy loss and the efﬁciency of devices how- ever requires further exploration. Here, through the hydroxyl (-OH) and acetoxy (-OCOMe) substitution at b-position of the IC terminal group, we developed two new synthetic acceptors, BTIC-OH-b and BTIC- OCOMe-b, which were designed to conﬁne the morphology aggregation. Introduction of an analogue as the third component provides a simple but efﬁcient way to further balance the short current density (Jsc) and open-circuit voltage (Voc), leading to a champion efﬁciency based on PBDB-T:PBDB-TF:BTIC-OCOMe- b, effectively as high as 12.45%. The results were examined mainly in terms of the morphology character- ization, electroluminescence external quantum efﬁciency (EQEEL), steady-state photoluminescence (PL) and transient technology. It suggested ﬁne-tuning of the morphology by ratio modulation, reduction of the energy loss, construction of a promising pathway for charge transfer in the ternary system and enhancing the carrier extraction. In this way, a ternary strategy with an analogue donor could provide more routes to higher-quality solar cells.

Organophosphine ligand derived sandwich-structural electrocatalyst for xygen evolution reaction

Zejun Sun, Wenjuan Xu, Liutao Guo, Qiang Han, Jianyi Gao, Jiaping Wang, Yanru Feng, Chengrui Li, Qionglin Liang, Hong-bin Sun, Yang Yang

2022, 70(7): 74-83. DOI: 10.1016/j.jechem.2022.02.005

Abstract ( 7 )

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The synchronous construction of metal phosphate and phosphorus-doped carbon structures is of great signiﬁcance to innovate the design, synthesis, and application of catalysts, as these phosphorus-containing composite materials have shown a remarkable contribution to electrocatalysts. However,their preparation procedure generally involves using large amounts of excess phosphorus sources for phosphorization, which inevitably release poisonous PH3 or dangerous phosphorus vapor. Here, a strat- egy for in-situ formation of FePO4 embedded in P-doped carbon 2D nano ﬁlm (FePO4/PdC) is developed using a highly integrated precursor, which is a small molecular organophosphine ligand, 1,10bis (diphenylphosphine) ferrocene (DPPF). The multi-source precursor DPPF that contains Fe, P, and C is molecular-vapor-deposited on the nickel foam (NF) supported ZIF-67 nanosheets to obtain the composite catalyst, namely DPPF-500/ZIF-67/NF. FePO4/PdC encapsulated the ZIF-67 derived Co/N-doped carbon matrix (CoNC) to form a sandwich structure FePO4/PdC@CoNC. The constructed catalyst shows good per- formance for OER, requiring an overpotential of only 297 mV to deliver 600 mA/cm2 with a Tafel slope of 42.7 mV dec^-1. DFT calculations demonstrate that the synergistic effects between the metal active center and P-doped carbon ﬁlm reduce the energy barriers and improve electron transport. This method of con- structing P-containing catalysts overcomes the demand for additional P sources to realize eco-friendly fabrication and yields a unique structure with good catalytic activity.

Implementation of a choline bis(triﬂuoromethylsulfonyl)imide aqueous electrolyte for low temperature EDLCs enabled by a cosolvent

Zhuanpei Wang, François Béguin

2022, 70(7): 84-94. DOI: 10.1016/j.jechem.2022.01.022

Abstract ( 9 )

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We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(triﬂuoromethylsulfonyl)imide (ChTFSI) electrolyte with a cosolvent enabling low-temperature operation down to -30 °C. For this purpose, a MgO-templated hierarchical carbon (MP98B) with an average mesopore diameter of 3.5 nm was prepared by pyrolysis of magnesium citrate hydrate at 900 °C. To reach lower temperatures, the melting point and viscosity of the aqueous electrolyte were reduced by mixing water (W) with an organic solvent (methanol, M, or isopropanol, I) of high dielectric constant and low viscosity. 5 mol kg^-1(5 m) ChTFSI in an optimized volume fraction of cosolvent, M_0.75W_0.25,and I_0.75W_0.25, showed the highest conductivity; the higher conductivity in M_0.75W_0.25(22.8 and 3.1 mS cm^-1at 20 and -30 °C, respectively) than in I_0.75W_0.25(8.5 and 0.5 mS cm^-1at 20 and -30 °C, respectively) is attributed to the lower viscosity of the M_0.75W_0.25solution. The electrochemical stability window (ESW) of 5 m ChTFSI in M_0.75W_0.25and I_0.75W_0.25(1.6 V) on an MP98B electrode was determined by applying the S-method. Meanwhile, by adjusting the mass ratio of the two electrodes, a MP98B/MP98B capacitor using the 5 m electrolyte in M_0.75W_0.25could operate with a good life span up to 1.6 V while exhibiting a better charge propagation, greater speciﬁc capaci- tance, and higher speciﬁc energy than in I_0.75W_0.25.

Transition metal carbonate anodes for Li-ion battery: fundamentals,synthesis and modiﬁcation

Rui Zhang, Qingfeng Fu, Peng Gao, Wang Zhou, Hui Liu, Chaohe Xu, Jian-Fang Wu, Chuanjun Tu, Jilei Liu

2022, 70(7): 95-120. DOI: 10.1016/j.jechem.2022.01.048

Abstract ( 12 )

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Even though transition metal carbonates (TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capac-ities, rich reserves and environmental friendliness as anodes for lithium-ion batteries (LIBs), they suffer from sluggish electronic/ionic conductivities and huge volume variation, which severely deteriorate the rate capacities and cycling performances. Understanding the intrinsic reaction mechanism and further developing ideal TMC-based anode with high speciﬁc capacity, excellent rate capabilities, and long-term cycling stability are critical for the practical application of TMCs. In this review, we ﬁrstly focus on the fundamental electrochemical energy-storage mechanisms of TMCs, in terms of conversion- reaction process, pseudocapacitance-type charge storage, valence change for charge storage and catalytic conversion mechanisms. Based on the reaction mechanisms, various modiﬁcation strategies to improve the electrochemical performance of TMCs are summarized, covering: (i) micro-nano structural engineer- ing, in which the inﬂuence factors on the morphology are discussed, and multiple architectures are listed; (ii) elemental doping, in which the intrinsic mechanisms of metal/nonmetal elements doping on the elec- trochemical performance are deeply explored; (iii) multifunctional compositing strategies, in which the speciﬁc affections on structure, electronic conductivity and chemo-mechanical stability are summarized. Finally, the key challenges and opportunities to develop high-performance TMCs are discussed and some solutions are also proposed. This timely review sheds light on the path towards achieving cost-effective and safe LIBs with high energy density and long cycling life using TMCs-based anode materials.

Unveiling anomalous lattice shrinkage induced by Pi-backbonding in Prussian blue analogues

Ju-Hyeon Lee, Jin-Gyu Bae, Hyeon Jeong Lee, Ji Hoon Lee

2022, 70(7): 121-128. DOI: 10.1016/j.jechem.2022.02.032

Abstract ( 6 )

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Transition-metal (TM)-based Prussian blue and its analogues (TM-PBAs) have attracted considerable attention as cathode materials owing to their versatile ion storage capability with tunable working volt- ages. TM-PBAs with different crystal structures, morphologies, and TM combinations can exhibit excel- lent electrochemical properties because of their unique and robust host frameworks with well-deﬁned < 100> ionic diffusion channels. Nonetheless, there is still a lack of understanding regarding the perfor- mance dependence of TM-PBAs on structural changes during charging/discharging processes. In this study, in situ X-ray diffraction and X-ray absorption ﬁne structure analyses elucidate the TM- dependent structural changes in a series of TM-PBAs during the charging and discharging processes. During the discharging process, the lattice volume of Fe-PBA increased while those of Ni- and Cu-PBAs decreased. This discrepancy is attributed to the extent of size reduction of the cyanometallate complex ([Fe(CN)6]) via pi-backbonding from Fe to C due to redox ﬂips of the low-spin Fe3+/2+ ion. This study pre- sents a comprehensive understanding of how TM selection affects capacity acquisition and phase transi- tion in TM-PBAs, a promising class of cathode materials.

Structural design for electrocatalytic water splitting to realize industrial-scale deployment: Strategies, advances, and perspectives

Xianwei Fu, Ruijuan Shi, Shilong Jiao, Mengmeng Li, Qiuye Li

2022, 70(7): 129-153. DOI: 10.1016/j.jechem.2022.02.010

Abstract ( 38 )

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The green hydrogen generation powered by renewable electricity promises the potential decarbonization of the hard-to-abate sector and is essential for the fulﬁllment of the Paris Agreement that attempts to limit the global average temperature rise in the range of 1.5-2.0 °C above the pre-industrial level by the end of this century. Tremendous efforts have been devoted to the optimization of the electrocatalytic performance of the catalysts under industrial-relevant current densities via rational structure design, which induces a preferential electron distribution that favors the adsorption/desorption behavior of the key intermediates, thus accelerating the reaction kinetics. In this review, a brief introduction of the current energy status will be ﬁrst presented to necessitate the importance of green hydrogen. Followed by the basic concepts and fundamental understanding of the reaction mechanisms, we present efﬁcient strategies for the enhancement of the electrocatalytic performance of the catalysts to meet the rigorous requirement under industrial conditions and the in-depth understanding behind the reinforce- ment will be brieﬂy discussed next. Then the recent advances regarding the rational design of electrocat- alysts operating at an industrial scale will be summarized. Finally, the challenges and perspectives in this thriving ﬁeld will be proposed from our point of view.

A feasible and effective solution-processed PCBM electron extraction layer enabling the high V_OCand efﬁcient Cu₂ZnSn(S, Se)₄devices

Licheng Lou, Yuancai Gong, Jiazheng Zhou, Jinlin Wang, Xiao Xu, Kang Yin, Biwen Duan, Huijue Wu, Jiangjian Shi, Yanhong Luo, Dongmei Li, Hao Xin, Qingbo Meng

2022, 70(7): 154-161. DOI: 10.1016/j.jechem.2022.02.009

Abstract ( 7 )

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Photo-generated carrier recombination loss at the CZTSSe/CdS front interface is a key issue to the open-circuit voltage (VOC) deﬁcit of Cu2ZnSnSxSe4-x(CZTSSe) solar cells. Here, by the aid of an easy-handling spin-coating method, a thin PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) layer as an electron extraction layer has been introduced on the top of CdS buffer layer to modify CZTSSe/CdS/ZnO-ITO (In2O3:Sn) interfacial properties. Based on Sn4+/DMSO (dimethyl sulfoxide) solution system, a total- area efﬁciency of 12.87% with a VOC of 529 mV has been achieved. A comprehensive investigation on the inﬂuence of PCBM layer on carrier extraction, transportation and recombination processes has been carried out. It is found that the PCBM layer can smooth over the CdS ﬁlm roughness, thus beneﬁcial for a dense and ﬂat window layer. Furthermore, this CZTSSe/CdS/PCBM heterostructure can accelerate carrier separation and extraction and block holes from the front interface as well, which is mainly ascribed to the downward band bending of the absorber and a widened space charge region. Our work provides a feasi- ble way to improve the front interfacial property and the cell performance of CZTSSe solar cells by the aid of organic interfacial materials.

Sputtering FeCu nanoalloys as active sites for alkane formation in CO₂hydrogenation

Zhiyan Si, Cederick Cyril Amoo, Yu Han, Jian Wei, Jiafeng Yu, Qingjie Ge, Jian Sun

2022, 70(7): 162-173. DOI: 10.1016/j.jechem.2022.02.039

Abstract ( 12 )

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Catalytic conversion of CO2 to high-value products is a crucial method to achieve targets of carbon diox-ide emissions peak and carbon neutralization. However, realizing a controllable product distribution in a single CO2 hydrogenation process is of great challenge. Herein, we prepared the CuFe nanoalloy catalyst that directly transforms CO2 to alkanes using physical sputtering method in mild condition. The charac- teristic results show that the proximity between Cu and Fe is the crucial factor to tunable products among the different catalysts. The formation of unique coordination of FeCu4 nanoalloys from high-energy sput- tering process provides close interaction between Cu and Fe, which is favorable to formation of low car- bon parafﬁn, however, a distant proximity and weak interaction will increase the selectivity of oleﬁns and alcohols. This work provides a general strategy for tuning target chemicals and enriches the viewpoints in CO2 hydrogenation.

Revealing the solid electrolyte interface on calcium metal anodes

Yumeng Zhao, Aoxuan Wang, Libin Ren, Xingjiang Liu, Jiayan Luo

2022, 70(7): 174-190. DOI: 10.1016/j.jechem.2022.02.022

Abstract ( 11 )

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Owing to its low potential, crustal abundances and environmental friendliness, calcium metal anode (CMA) is emerging as a powerful contender in post-lithium era. However, the passivation of CMA fatally hinders its development. Recently, several feasible electrolytes have been developed. Nevertheless, as a pivotal part, the solid electrolyte interface (SEI) formed on CMA has not been paid enough attention to. In this review, based on the passivation mechanism of CMA, the favorable composition of SEI is emphasized with the corresponding electrolytes. It is considered that boron-containing and organic- inorganic hybrid SEI might be preferred. By comparing electrolytes and SEI on CMA with lithium and magnesium metal anodes, the root causes of CMA passivation are further elaborated, enlightening rational design rules of suitable SEI. Furthermore, some noteworthy details when assembling secondary calcium metal batteries (CMBs) are put forward. It is expected that deeper understanding of SEI on CMA will promote the development of CMBs.

Double interface modiﬁcation promotes efﬁcient Sb₂Se₃solar cell by tailoring band alignment and light harvest

Weihuang Wang, Zixiu Cao, Xu Zuo, Li Wu, Jingshan Luo, Yi Zhang

2022, 70(7): 191-200. DOI: 10.1016/j.jechem.2022.02.013

Abstract ( 9 )

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The band alignment at the front interfaces is crucial for the performance of Sb2Se3 solar cell with super-strate conﬁguration. Herein, a SnO2/TiO2 thin ﬁlm, demonstrated beneﬁcial for carrier transport in Sb2Se3 device by the ﬁrst-principle calculation and experiment, is proposed to reduce the parasitic absorption caused by CdS and optimize the band alignment of Sb2Se3 solar cell. Thanks to the desirable transmit- tance of SnO2/TiO2 layer, the Sb2Se3 solar cell with SnO2/TiO2/(CdS-38 nm) electron transport layer per- formances better than (CdS-70 nm)/Sb2Se3 solar cell. The optimized band alignment, the reduced interface defects and the decreased current leakage of Sb2Se3 solar cell enable the short-circuit current density, ﬁll factor, open-circuit voltage and efﬁciency of the Sb2Se3 solar cell increase by 26.7%, 112%, 33.1% and 250% respectively when comparing with TiO2/Sb2Se3 solar cell without modiﬁcation. Finally, an easily prepared SnO2/TiO2/CdS ETL is successfully applied on Sb2Se3 solar cell by the ﬁrst time and con- tributes to the best efﬁciency of 7.0% in this work, which is remarkable for Sb2Se3 solar cells free of hole transporting materials and toxic CdCl2 treatment. This work is expected to provide a valuable reference for future ETL design and band alignment for Sb2Se3 solar cell and other optoelectronic devices.

A dynamic inﬁltration technique to synthesize nanolayered cathodes for high performance and robust solid oxide fuel cells

Saeed Ur Rehman, Ho-Seon Song, Hye-Sung Kim, Muhammad Haseeb Hassan, Dong-Woo Joh, Rak-Hyun Song, Tak-Hyoung Lim, Jong-Eun Hong, Seok-Joo Park, Seung-Bok Lee

2022, 70(7): 201-210. DOI: 10.1016/j.jechem.2022.02.052

Abstract ( 14 )

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Solution inﬁltration is a popular technique for the surface modiﬁcation of solid oxide fuel cell (SOFC) cathodes. However, the synthesis of nanostructured SOFC cathodes by inﬁltration is a tedious process that often requires several inﬁltration and high temperature (≥ 500 °C) calcination cycles. Moreover, fab- ricating large-area nanostructured cathodes via inﬁltration still requires serious attention. Here, we pro- pose a facile and scalable urea assisted ultrasonic spray inﬁltration technique for nanofabrication of SOFC cathodes. It is demonstrated that by using urea as a precipitating agent, the calcination after each inﬁl- tration cycle can be omitted and the next inﬁltration can be performed just after a drying step (≤ 100 °C). Finally, the precipitates can be converted into a desired catalyst phase in single calcination thus, a nanos- tructured cathode can be fabricated in a much faster manner. It is also shown that the low calcination temperature of the cathode (≤ 900 °C) can produce highly durable SOFC performance even without employing a Ce0.9Gd0.1O2 (GDC) diffusion barrier layer which provides the ease of SOFC fabrication. While coupling with an ultrasonic spray technique, the urea assisted inﬁltration can be scaled up for any desired cathode area. La0.6Sr0.4Co0.2Fe0.8O3 nanolayered cathode was fabricated and it was character- ized by scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron micro- scopy (TEM) techniques. SEM showed the formation of a nanolayer cathode just after 5 cycles of the urea assisted inﬁltration while the XRD and TEM conﬁrmed the phase and stoichiometric uniformity of the ~100 nm cathode nanolayer. The effectiveness of the newly developed technique was further veriﬁed by the stable operation of a GDC buffer layer free SOFC having an active cathode area of 25 cm2 during a 1200 h durability test. The research outcomes propose urea assisted ultrasonic spray inﬁltration as a facile, scalable, and commercially viable method for the fabrication of durable nanostructured SOFC cathodes.

Co nanoparticles wrapped with graphitic layers via optimizing electron ransfer

Yu Feng, Kexin Song, Wei Zhang, Xinyan Zhou, Seung Jo Yoo, Jin-Gyu Kim, Sifan Qiao, Yugang Qi, Xu Zou, Zhongjun Chen, Tingting Qin, Nailin Yue, Zizhun Wang, Dabing Li, Weitao Zheng

2022, 70(7): 211-218. DOI: 10.1016/j.jechem.2022.01.047

Abstract ( 7 )

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The poor stability of non-noble metal catalysts in oxygen reduction reaction (ORR) is a main bottleneck that limits their big-scale application in metal-air batteries. Herein, we construct a chainmail catalyst (Co-NC-AD) with outstanding stability, via the competitive complexation and post absorption strategy, consisting of highly graphitic layers wrapped uniform-size Co nanoparticles (Co-NPs). Experiments com- bined with density functional theory (DFT) calculations jointly conﬁrmed that the electron transfer occurred from the inner Co-NPs to the external graphitic layers. It facilitated the adsorption process of oxygen molecules and the hybridization of the O-2p and C-1p orbitals, which accelerated the ORR reac- tion kinetics. Consequently, our prepared Co-NC-AD shows excellent ORR activity, offered with a more positive initial potential (Eonset = 0.95 V) and half-wave potential (E1/2 = 0.86 V). The remarkable stability and resistance of methanol poisoning are merited from the protection effect of stable graphitic layers. In addition, the high electrochemical performance of Co-NC-AD-based zinc-air battery demonstrates their potential for practical applications. Therefore, our work provides new ideas for the design of nano- conﬁned catalysts with high stability and activity.

Tandem catalysis on adjacent active motifs of copper grain boundary for efﬁcient CO₂electroreduction toward C₂products

Tao Luo, Kang Liu, Junwei Fu, Shanyong Chen, Hongmei Li, Junhua Hu, Min Liu

2022, 70(7): 219-223. DOI: 10.1016/j.jechem.2022.02.050

Abstract ( 8 )

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Copper (Cu) is a special electrocatalyst for CO2 reduction reaction (CO2RR) to multi-carbon products. Experimentally introducing grain boundaries (GBs) into Cu-based catalysts is an efﬁcient strategy to improve the selectivity of C2+ products. However, it is still elusive for the C2+ product generation on Cu GBs due to the complex active sites. In this work, we found that the tandem catalysis pathway on adja- cent active motifs of Cu GB is responsible for the enhanced activity for C2+ production by ﬁrst principles calculations. By electronic structure analysis shows, the d-band center of GB site is close to the Fermi level than Cu(100) facet, the Cu atomic sites at grain boundary have shorter bond length and stronger bonding with *CO, which can enhance the adsorption of *CO at GB sites. Moreover, CO2 protonation is more favorable on the region III motif (0.84 eV) than at Cu(100) site (1.35 eV). Meanwhile, the region II motif also facilitate the C-C coupling (0.72 eV) compared to the Cu(100) motif (1.09 eV). Therefore, the region III and II motifs form a tandem catalysis pathway, which promotes the C2+ selectivity on Cu GBs. This work provides new insights into CO2RR process.

Ni nanoparticles conﬁned by yolk-shell structure of CNT-mesoporous carbon for electrocatalytic conversion of CO₂: Switching CO to formate

Juan Du, Aibing Chen

2022, 70(7): 224-229. DOI: 10.1016/j.jechem.2022.02.020

Abstract ( 9 )

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Electrochemical reduction of CO₂(CO₂ER) to formate has been a promising route to produce value-added chemicals. Developing low-cost and efﬁcient electrocatalysts with high product selectivity is still a grand challenge. Herein, a novel Ni nanoparticles-anchored CNT coated by mesoporous carbon with yolk-shell structure (CNT/Ni@mC) catalysis was designed for CO₂ER. Ni nanoparticles were conﬁned in the cavity between CNT and mesoporous carbon shell and the conﬁned space can be controlled by tuning the amount of silica precursor. The mesoporous carbon shell and conﬁned space are beneﬁcial to charge transmission during CO₂ER. In contrast to previous studies, the CNT/Ni@mC catalyst presents selectivity toward formate rather than CO. Electrochemical in situ attenuated total reﬂection Fourier transform infrared spectroscopy measurements indicate the presence of a COO* intermediate that converts to for- mate under CO₂ER conditions. The well-deﬁned structural feature of the conﬁned space of the Ni-based catalyst for selective CO₂ER to formate may facilitate in-depth mechanistic understandings on structural factors that affect CO₂ER performance.

Rational design ternary platinum based electrocatalysts for effective methanol oxidation reaction

Hao Tian, Daoxiong Wu, Jing Li ⇑, Junming Luo, Chunman Jia, Zhongxin Liu, Wei Huang, Qi Chen, Chong Michael Shim, Peilin Deng, Yijun Shen, Xinlong Tian

2022, 70(7): 230-235. DOI: 10.1016/j.jechem.2022.02.021

Abstract ( 9 )

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Exploring effective, durable, and affordable electrocatalysts of methanol oxidation reaction (MOR) is of vital signiﬁcance for the industrial application of direct methanol fuel cells. Herein, an efﬁcient, general, and expandable method is developed to synthesis two-dimensional (2D) ternary PtBiM nanoplates (NPLs), in which various M (Co, Ni, Cu, Zn, Sn) is severed as the third component to the binary PtBi sys- tem. The MOR performance of PtBiM NPLs is entirely investigated, demonstrating that both the MOR activity and durability is enhanced with the introduction of the additional composition. Pt₃Bi₃Zn NPLs shows much higher MOR activity and stability than that of the PtBi counterparts, not to mention the cur- rent advanced PtRu/C and Pt/C catalysts. The prominent performances are attributed to the modulated electronic structure of the surface Pt in PtBi NPLs by the addition of Zn, resulting in a weakened afﬁnation between Pt and the adsorbed poisoning species (mainly CO) compared with PtBi NPLs, veriﬁed by density functional theory (DFT) calculations. In addition, the absorbed OH can be generated on the surface of Zn atom due to its favorable water activation properties, thus the CO removal on the adjacent Pt atoms is accelerated, further leading to a high activity and anti-poisoning performance of the resulting Pt₃Bi₃Zn catalyst. This work provides new insights and robust strategy for highly efﬁcient MOR electrocatalyst with extraordinary anti-poisoning performance and stability.

Hydrophilic bi-functional B-doped g-C₃N₄hierarchical architecture for excellent photocatalytic H₂O₂production and photoelectrochemical water splitting

Yang Ding, Soumyajit Maitra, Chunhua Wang, Runtian Zheng, Meiyu Zhang, Tarek Barakat, Subhasis Roy, Jing Liu, Yu Li, Tawﬁque Hasan, Bao-Lian Su

2022, 70(7): 236-247. DOI: 10.1016/j.jechem.2022.02.031

Abstract ( 8 )

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Graphitic carbon nitride (g-C3N4) has attracted great interest in photocatalysis and photoelectrocatalysis. However, their poor hydrophilicity poses a great challenge for their applications in aqueous environment. Here, we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C3N4 nanoplatelets. Such hierarchical B-doped g-C3N4 material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium, leading to an excellent photocatalytic H2O2 production rate of 4240.3 μM g-1 h-1, 2.84, 2.64 and 2.13 times higher than that of the bulk g-C3N4, g-C3N4 nanoplatelets and bulk B doped g-C3N4, respectively. Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 mA cm-2 at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting. This work makes a fundamental improvement towards large-scale exploitation of highly active, hydrophilic and stable metal-free g-C3N4 photocatalysts for various practical applications.

Surface-roughened current collectors for anode-free all-solid-state batteries

Donghee Gu, Hyoungchul Kim, Jong-Ho Lee, Sangbaek Park

2022, 70(7): 248-257. DOI: 10.1016/j.jechem.2022.02.034

Abstract ( 13 )

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Anode-free all-solid-state batteries (AFASSBs), composed of a fully lithiated cathode and a bare current collector (CC) that eliminates excess lithium, can maximize the energy density (because of a compact cell configuration) and improve the safety of solid-state systems. Although significant progress has been made by modifying CCs in liquid-based anode-free batteries, the role of CCs and the mechanism of Li formation on CCs in AFASSBs are still unexplored. Here, we systematically investigate the effect of the surface roughness of the CCs on the Li plating/stripping behavior in AFASSBs. The results show that the moderately roughened CC substantially improves the Coulombic efficiency and cycle stability of AFASSBs owing to the increased contact points between the solid electrolyte and the roughened CC. In contrast, the excessively roughened CC deteriorates the performance owing to the contact loss. Moreover, an ex situ interface analysis reveals that the roughened surface of the CC could suppress the interfacial degradation during the Li ion extraction from a sulfide solid electrolyte to a CC. This provides an indication to the origin that hinders the electrochemical performance of AFASSBs. These findings show the potential for the application of surface-engineered CCs in AFASSBs and provide guidelines for designing advanced CCs.

Electron modulation of cobalt carbonate hydroxide by Mo doping for urea-assisted hydrogen production

Siyu Zheng, Hongye Qin, Xuejie Cao, Tongzhou Wang, Wenbo Lu, Lifang Jiao

2022, 70(7): 258-265. DOI: 10.1016/j.jechem.2022.02.023

Abstract ( 17 )

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Combining urea oxidation reaction (UOR) with hydrogen evolution reaction (HER) is an effective method for energy saving and highly efficient electrocatalytic hydrogen production. Herein, molybdenum-incorporated cobalt carbonate hydroxide nanoarrays (CoxMoyCH) are designed and synthesized as a bifunctional catalyst towards UOR and HER. Benefiting from the Mo doping, the dispersed nanoarray structure and redistributed electron density, the CoxMoyCH catalyst display outstanding catalytic performance and durability for both HER and UOR, affording the overpotential of 82 mV for HER and delivering a low potential of the 1.33 V for UOR (vs. reversible hydrogen electrode, RHE) to attain a current density of 10 mA cm-2, respectively. Remarkably, when CoxMoyCH was applied as bifunctional catalyst in a two-electrode electrolyzer, a working voltage of 1.40 V is needed in urea-assisted water electrolysis at 10 mA cm-2 and without apparent decline for 40 h, outperforming the working voltage of 1.51 V in conventional water electrolysis.

Investigation on process mechanism of a novel energy-saving synthesis for high performance Li₄Ti₅O₁₂anode material

Guochuan Wang, Hongmei Wang, Guangqiang Ma, Xinhe Du, Liyu Du, Peng Jing, Yanqing Wang, Kaipeng Wu, Hao Wu, Qian Wang, Yun Zhang

2022, 70(7): 266-275. DOI: 10.1016/j.jechem.2022.02.056

Abstract ( 9 )

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Li₄Ti₅O₁₂ (LTO) anode material demonstrates superior cycling performance due to its stable spinel structure and high lithiation/de-lithiation potential. Herein, a novel energy-saving solid-phase synthesis route for LTO has been successfully designed, employing the cheap industrial intermediate product of metatitanic acid (HTO) as titanium source. Through the in-situ Fourier transform infrared spectroscopy (FTIR) and ex-situ X-ray diffraction (XRD), it is revealed for the first time that the amorphous crystal structure of HTO is more conducive for the Li⁺ insertion, making it possible to prepare LTO at a relatively lower sintering temperature. Utilizing the dehydration carbonization reaction between glucose and sulfuric acid, an ingenious strategy of glucose pre-coating is adopted to avoid the generation of Li₂SO₄ impurity caused by the residual sulfuric acid on the surface of HTO, which meanwhile enhances the conductivity and inhibits the particle growth of LTO. The obtained ALTO@C anode material consequently exhibits excellent electrochemical performance that 132.0 mAh g^-1 is remained even at 20 C, and ultra low decay rate of 0.015% per cycle is achieved during 1000 cycles at 2 C. Remarkably, LiCoO₂//ALTO@C full cell delivers conspicuous low-temperature property (130.7 mAh g^-1 at 0.5 C and almost no attenuation after 300 cycles under -20 °C).

A one-for-all strategy of polyimide coating layer for resolving the comprehensive issues of phosphorus anode

Muyao Han, Shaojie Zhang, Yu Cao, Chengyu Han, Xu Li, Yiming Zhang, Zhanxu Yang, Jie Sun

2022, 70(7): 276-282. DOI: 10.1016/j.jechem.2022.02.035

Abstract ( 10 )

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Phosphorus is a promising anode with high capacity (2596 mAh g^-1 and 6075 ∼ 6924 mAh cm^-3), low lithium-ion diffusion barrier (0.08 eV), and appropriate lithiation potential (∼0.7 V vs Li⁺/Li). However, it faces the problems of huge volume expansion (∼300%), low electronic conductivity (10^-14 ∼ 10² S cm^-1), soluble intermediates (lithium polyphosphides, Li_xPs), degradation in air, and low thermal stability. In this work, phosphorus/carbon nanotube composites were coated with a polyimide layer, which plays the roles of a buffer layer to relieve the volume expansion of phosphorus, an obstruct layer to confine Li_xPs, an inert layer to prevent the degradation of phosphorus in air, a heat resistant layer to improve the thermal stability of the anode. The resulting composites (P/CNT@PI) display high capacity retention of 798.1 mAh g^-1 after 150 cycles at 1 A g^-1, achieving 17 times as much as the control sample (P/CNT).

High rate and ultralong life ﬂexible all-solid-state zinc ion battery based on electron density modulated NiCo₂O₄nanosheets

Wenda Qiu, Yunlei Tian, Zhenchao Lin, Shuting Lin, Zhangqi Geng, Kaitao Huang, Aihua Lei, Fuchun Huang, Huajie Feng, Fengze Ding, Yu Li, Xihong Lu

2022, 70(7): 283-291. DOI: 10.1016/j.jechem.2022.02.012

Abstract ( 20 )

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The development of zinc ion batteries (ZIBs) with large capacity, high rate, and durable cathode material is a crucial and urgent task. NiCo₂O₄ (NCO) has received ever-growing interest as a potential cathode material for ZIBs, owing to the high theoretical capacity, rich source, cost-effective, and versatile redox nature. However, due to the slow dynamics of the NCO electrodes, its practical application in high-performance systems is severely limited. Herein, we report an electron density modulated NCO nanosheets (N-NCO NSs) with high-kinetics Zn²⁺-storage capability as an additive-free cathode for flexible all-solid-state (ASS) ZIBs. By virtue of the enhanced electronic conductivity, improved reaction kinetics, and increased active sites, the optimized N-NCO NSs electrode delivers a high capacity of 357.7 mAh g^-1 at 1.0 A g^-1 and a superior rate capacity of 201.4 mAh g^-1 at 20 A g^-1. More importantly, a flexible ASS ZIBs device is manufactured using a solid polymer electrolyte of a poly (vinylidene fluoride hexafluoropropylene) (PVDF-HFP) film. The flexible ASS ZIBs device shows superb durability with 80.2% capacity retention after 20,000 cycles and works well in the range of -20-70 °C. Furthermore, the flexible ASS ZIBs achieves an impressive energy density as high as 578.1 W h kg^-1 with a peak power density of 33.6 kW kg^-1, substantially outperforming those latest ZIBs. This work could provide valuable insights for constructing high-kinetics and high-capability cathodes with long-term stability for flexible ASS ZIBs.

Progress of fundamental mechanism of formic acid decomposition and electrooxidation

Xin Liu, Timo Jacob, Wang Gao

2022, 70(7): 292-309. DOI: 10.1016/j.jechem.2022.02.017

Abstract ( 21 )

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Formic acid (HCOOH) is considered as a promising viable fuel-cell ingredient for low temperature proton-exchange membrane fuel cells as a consequence of their high safety and energy density. As one prototype reaction, the study of HCOOH decomposition and electrooxidation is also helpful to understand the reaction mechanism of other small molecular organics. Herein, we present a comprehensive overview of HCOOH decomposition and electrooxidation in different environment conditions and analyze the reaction mechanism from both experimental and theoretical point of view. Furthermore, we discuss the known strategies for improving the performance of HCOOH decomposition and electrooxidation catalysts. Finally, this review presents a prospect for the future study of HCOOH decomposition and electrooxidation.

Rational catalyst design and interface engineering for electrochemical CO₂reduction to high-valued alcohols

Lingxi Zhou, Ruitao Lv

2022, 70(7): 310-331. DOI: 10.1016/j.jechem.2022.02.033

Abstract ( 24 )

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Electrochemical CO₂ reduction (eCO₂RR) is an emerging strategy to address the global carbon balance issues and fulfill the carbon-neutral goal through converting CO₂ to value-added chemicals/fuels driven by renewable energy sources. The production of highly reduced carbon compounds beyond CO and formate, especially oxygenate alcohol products with high energy densities and large global market capacities, is particularly desirable for practical applications. However, the building of alcohol-selective eCO₂RR electrocatalysis systems to overcome the high overpotential and poor durability remains a big challenge. Recently, diverse strategies have been developed for rational catalyst design towards alcohol productions from eCO₂RR on the basis of the corresponding reaction mechanisms. In this review article, we firstly highlight recent advances in fundamental understanding of mechanisms in three electrochemical CO₂-alcohol reaction pathways. Then, the design strategies focused on catalyst and interface design are summarized for building alcohol-selective eCO₂RR electrocatalysis systems. The advanced characterization techniques are also discussed to provide more insights into eCO₂RR-to-alcohols processes. Finally, the remaining challenges and perspectives for promoting eCO₂RR to alcohols are proposed.

Promotion effect of sulfur impurity in alumina support on propane dehydrogenation

Xin-Qian Gao, Wen-Cui Li, Bin Qiu, Jian Sheng, Fan Wu, An-Hui Lu

2022, 70(7): 332-339. DOI: 10.1016/j.jechem.2022.02.048

Abstract ( 14 )

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：Alumina materials are widely applied either as a catalyst or support in various industrial catalytic processes. Impurities in alumina that are unfriendly to catalytic performance are inevitably present during the production processes. Facing this problem, we here report that the use of sulfur-containing alumina as the support can generate active alumina-supported platinum catalyst, which exhibits superior propylene selectivity and anti-coking ability during propane dehydrogenation. It demonstrated that the sulfur impurity in alumina is not entirely detrimental. During the reduction process, the formation of gas-phase sulfur species increased the electrons and poisoned unsaturated sites of platinum particles. The sulfur impurity in alumina can be removed through a hydrogen reduction process, and the degree of desulfurization is correlated with the operating temperature. This study demonstrated that the rational use of impurity will contribute to the design of a catalyst with high reactivity for potential applications.

Understanding ﬂuorine-free electrolytes via small-angle X-ray scattering

Kun Qian, Zhou Yu, Yuzi Liu, David J. Gosztola, Randall E. Winans, Lei Cheng, Tao Li

2022, 70(7): 340-346. DOI: 10.1016/j.jechem.2022.02.043

Abstract ( 11 )

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Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. Here, we compare the solvation phenomenon of sodium tetraphenylborate (NaBPh₄) salt dissolved in organic solvents of propylene carbonate (PC), 1,2-dimethoxyethane (DME), acetonitrile (ACN) and tetrahydrofuran (THF). Small-angle X-ray scattering (SAXS) reveals a unique two-peak structural feature in this salt-concentrated PC electrolyte, while solutions using other solvents only have one scattering peak. Molecular dynamics (MD) simulations further reveal that there are anion-based clusters in addition to the short-range charge ordering in the concentrated NaBPh₄/PC electrolyte. Raman spectroscopy confirms the existence of considerable contact ion pairs (CIPs). This work emphasizes the importance of global and local structural analysis, which will provide valuable clues for understanding the structure-performance relationship of electrolytes.

A durable Ni/La-Y catalyst for efficient hydrogenation of γ-valerolactone into pentanoic biofuels

Jiang He, Lu Lin, Meng Liu, Caixia Miao, Zhijie Wu, Rui Chen, Shaohua Chen, Tiehong Chen, Yang Su, Tao Zhang, Wenhao Luo

2022, 70(7): 347-355. DOI: 10.1016/j.jechem.2022.02.011

Abstract ( 25 )

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Zeolite-supported metal catalysts containing hydrogenation centers and acid sites are promising in the chemoselective hydrogenation of biomass platform molecules into value-added chemicals and fuels. The primary challenge of employing such bifunctional catalysts for biomass conversion lies in catalyst stability in the liquid phase under harsh conditions. Herein, we have prepared a Ni/La-Y nanocatalyst via an improved wet impregnation method. Compared with Ni nanoparticles on H-Y, La addition shows a significantly enhanced stability and performance in the continuous liquid-phase hydrogenation of γ-valerolactone (GVL) into ethyl pentanoate (EP) at 200 °C for 1000 h. Complementary characterization studies reveal that La addition in the metal/zeolite catalyst not only efficiently modulates the acid property of the zeolite to alleviate coke formation, but also suppresses zeolite dealumination and metal agglomeration and leaching upon catalysis over a 1000 h period. These findings provide an efficient approach for improving the stability of zeolite-supported bifunctional catalysts, leading to potential application in hydrogen-assisted biomass valorization under the liquid-phase conditions.

Fabricating a PVDF skin for PEO-based SPE to stabilize the interface both at cathode and anode for Li-ion batteries

Qi Ye, Haoyue Liang, Shuhao Wang, Can Cui, Cheng Zeng, Tianyou Zhai, Huiqiao Li

2022, 70(7): 356-362. DOI: 10.1016/j.jechem.2022.02.037

Abstract ( 13 )

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Poly (ethylene oxide) (PEO)-based solid polymer electrolyte is always the most promising candidate for preparing thinner, lighter and safer lithium-ion batteries. However, the lithium dendrites growth of lithium anode and the high-voltage oxidation of cathode are easy to cause the PEO-based battery failure. The way to deal with the different challenges on both sides of the anode and cathode is pursued all the time. In this study, we reported a new strategy to construct the PVDF/PEO/PVDF three-layer structure for solid polymer electrolyte (marked as PVDF@PEO) using PVDF as the functional “skin”. The PVDF@PEO electrolyte can effectively prevent from the lithium dendrites, and shows a stable cycling life over 1000 h in the Li/PVDF@PEO/Li cell. In addition, the PVDF@PEO electrolyte exhibits higher oxidation resistance and can be matched with high-voltage LiCoO₂ cathode. The Li/PVDF@PEO/ LiCoO₂ cell delivered a specific capacity of about 150 mAh g^-1 over 150 cycles and maintained good cycling stability. Our research provides insights that the polymer electrolytes constructed with PVDF functional “skin” can simultaneously meet the challenges of both anode and cathode in solid-state lithium-ion batteries (SSLIBs).

Deep eutectic solvent-based polymer electrolyte for solid-state lithium metal batteries

Panpan Dong, Xiahui Zhang, Kee Sung Han, Younghwan Cha, Min-Kyu Song

2022, 70(7): 363-372. DOI: 10.1016/j.jechem.2022.02.026

Abstract ( 31 )

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Poly(ethylene) oxide (PEO)-based electrolytes have been widely studied for solid-state lithium batteries while their ionic conductivity and lithium-ion transference number still need to be further improved. Herein, using the combined experimental and theoretical approach, we demonstrate a novel, solid-state PEO-deep eutectic solvent (DES) electrolyte for the first time. We found that the in situ formation of DES can reduce the crystallinity of PEO matrix and more Li⁺ ions can move freely owing to the weakened coordination between ether oxygens and Li-ions. Besides, we show that more Li⁺ ions can be dissociated from Li salts in PEO-DES electrolyte using the molecular dynamics simulations. Such liquid-free PEO-DES electrolytes showed good ionic conductivity (2.1 × 10^-4 S cm^-1) which is 160% higher than that of conventional PEO-LiTFSI (8.1 × 10^-5 S cm^-1) electrolyte at 60 °C. Additionally, the PEO-DES electrolyte showed 136% increase of Li-ion transference number (0.33) compared with ionic liquid-doped PEO-LiTFSI (0.14) at 60 °C. Moreover, the PEO-DES exhibited good compatibility with Li metal and stable Li plating/stripping behavior with little morphology change of Li metal. This research also provides new insights into the enhancement mechanisms of novel polymer electrolytes, improving our fundamental understanding of critical challenges that have impeded the adoption of solid-state lithium metal batteries.

In situ revealing the reconstruction behavior of monolayer rocksalt CoO nanosheet as water oxidation catalyst

Weiqi Guo, Haolin Luo, Dongxu Fang, Zhi Jiang, Jiasheng Chi, Wenfeng Shangguan

2022, 70(7): 373-381. DOI: 10.1016/j.jechem.2022.02.049

Abstract ( 9 )

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The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst. Compared with well-investigated cobalt-based materials, the reconstruction of rocksalt CoO with purely Co²⁺ in octahedral (Oh) coordination has not been revealed in detail. Herein, monolayer CoO supported on reduced graphene oxide (rGO) was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere. The structure evolution of two-dimension (2D) CoO/rGO during OER was revealed by in situ X-ray absorption spectroscopy (XAS). The transition from CoO toward Co₃O₄ already occurred at open circuit potential, further enhanced at 1.23 V (vs. RHE). The CoO_x(OH)_y was determined as the active phase at 1.53 V, displaying a tetrahedral Co coordination defective spinel Co₃O₄ with the Co-O shell that featured the (oxy)hydroxide, not the standard CoOOH. After OER, the irreversible transition from CoO to Co₃O₄ was observed. In contrast, in situ Raman spectra revealed a reversible amorphization process on Co₃O₄/rGO under operation conditions. Furthermore, this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.

Enhanced electrochemical CO₂-to-C₂₊conversion from synergistic interaction between terrace and step sites on monocrystalline high-index Cu facets

Chenyuan Zhu, Zhibin Zhang, Lixiang Zhong, Siwen Zhao, Guoshuai Shi, Bowen Wu, Huoliang Gu, Jing Wu, Xinyang Gao, Kaihui Liu, Liming Zhang

2022, 70(7): 382-387. DOI: 10.1016/j.jechem.2022.02.027

Abstract ( 8 )

PDF (1866KB) ( 11 )

EPR study of charge separation associated states and reversibility of surface bound superoxide radicals in SrTiO₃photocatalyst

Xianwen Zhang, Zheng Li, Bin Zeng, Can Li, Hongxian Han

2022, 70(7): 388-393. DOI: 10.1016/j.jechem.2022.02.038

Abstract ( 9 )

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Understanding the processes of charge generation, transfer and capture is important for the design and synthesis of efficient photocatalysts. In this work, light-induced charge separation and effect of O₂ on electron transfer processes in SrTiO₃ were investigated by electron paramagnetic resonance (EPR). It was found that photoinduced electron transfer from O^2- to Ti⁴⁺ produced Ti³⁺ and O^- redox radical pairs under vacuum condition. Under oxygen atmosphere, however, surface bound superoxide radicals O₂^- were formed by electron reduction of adsorbed oxygen at initial photoirradiation stage, and quenched by the reverse electron transfer to Ti⁴⁺ upon further photoirradiation. Formation of long-lived charge separation associated [Ti³⁺---O^-] species and the reversibility of surface bound superoxide radicals mediating the processes of photogenerated electrons may be accountable for the high activity of SrTiO₃ in photocatalytic water splitting reaction.

Boosting hydrogen and chemicals production through ethanol electro-reforming on Pt-transition metal anodes

Alberto Rodríguez-Gómez, Fernando Dorado, Paula Sánchez, Ana Raquel de la Osa

2022, 70(7): 394-406. DOI: 10.1016/j.jechem.2022.02.028

Abstract ( 8 )

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：The aim of this work is to boost the combined hydrogen and added-values compounds generation (acetaldehyde, acetic acid and ethyl acetate) through ethanol electrochemical reforming using bimetallic anodes. In particular, the influence of the secondary metal on the electrochemical performance as well as on the product distribution was studied. For that purpose, PtX/C electrocatalysts (where X corresponds to Cu, Co, Ni and Ru) were synthesized by the modified polyol method and tested in both half-cell and proton exchange membrane (PEM) cell configurations. Characterization results showed that incorporation of Ni and Co into the Pt matrix enhances the morphological properties of the material, providing smaller crystallite sizes, higher active surface areas and hence, better dispersion when comparing to Ru and Cu-based electrocatalysts. Ethanol oxidation reaction (EOR) was evaluated by cyclic, linear voltammetry and chronopotentiometry assays. PtCo/C and PtNi/C exhibited the highest electrocatalytic activity at high polarization levels, which translate into an improvement of more than 30% (up to 1050 mA cm^-2) in the hydrogen production and chemical yields. On the other hand, PtRu/C results more advantageous for a lower potential interval (<0.85 V) promoting the acetic acid production despite sacrificing ethanol conversion. PtCu/C presented the lowest results in both electrochemical performance and product distribution. Such differences in the electrochemical performance can be rationalized in terms of the synergistic effect between both metals (particle size distribution, grade of dispersion and hydrophilic behavior), which demonstrate that the incorporation of a different secondary metal plays an essential role in the EOR development.

Heterostructured Pd/PdO nanowires for selective and efﬁcient CO₂electroreduction to CO

Tian-Jiao Wang, Wen-Sheng Fang, Yi-Ming Liu, Fu-Min Li, Pei Chen, Yu Chen

2022, 70(7): 407-413. DOI: 10.1016/j.jechem.2022.03.001

Abstract ( 8 )

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Palladium (Pd) nanostructures are highly promising electrocatalysts for the carbon dioxide electrochemical reduction (CO₂ER). At present, it is still challenge for the synthesis of Pd nanostructures with high activity, selectivity and stability. In this work, a facile Pd^II-complex pyrolysis method is applied to synthesize the high-quality one-dimensional heterostructured Pd/PdO nanowires (Pd/PdO H-NWs). The as-prepared Pd/PdO H-NWs have a large electrochemically active surface area, abundant defects and Pd/PdO heterostructure. Electrochemical measurement results reveal that Pd/PdO H-NWs exhibit up to 94% CO Faraday efficiency with a current density of 11.6 mA cm^-2 at an applied potential of -0.8 V. Meanwhile, Pd/PdO H-NWs can achieve a stable catalytic process of 12 h for CO₂ER. Such outstanding CO₂ER performance of Pd/PdO H-NWs has also been verified in the flow cell test. The density functional theory calculations indicate that Pd/PdO heterostructure can significantly weaken the CO adsorption on Pd sites, which improves the CO tolerance and consequently enhances the catalytic performance of Pd/PdO H-NWs for CO₂ER. This work highlights a facile complex pyrolysis strategy for the synthesis of Pd-based CO₂ER catalysts and provides a new application instance of metal/metal oxide heterostructure in electrocatalysis.

In-situ reconstruction of catalysts in cathodic electrocatalysis: New insights into active-site structures and working mechanisms

Wenbiao Zhang, Yang Yang, Yi Tang, Qingsheng Gao

2022, 70(7): 414-436. DOI: 10.1016/j.jechem.2022.02.036

Abstract ( 15 )

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： Cathodic electrocatalytic reactions, such as hydrogen evolution and CO₂/N₂ reduction, are the key processes that store intermittent electricity into stable chemical energy. Although a great progress has been made to boost activity and selectivity via elaborative catalyst design, the structure-property relationships have not been sufficiently understood in the context of surface reconfiguration under working conditions. Recent efforts devoted to tracking dynamic evolution of electrocatalysts using in-situ and/or operando techniques gave new insights into the real structure and working mechanism of active sites, and provided principles to design better catalysts. The achievement of cathodic electrocatalysts in this subject is herein summarized, focusing on the correlations between reconstructed surface and electrocatalytic performance. Briefly, the thermodynamics of reconstruction at cathodes is discussed at first, and then the representative progresses in H₂ evolution and CO₂/N₂ reduction are introduced in sequence to acquire insights into electrochemical processes on in-situ reconfigured surfaces or interfaces. Finally, a perspective is offered to guide future investigations. This review is anticipated to shed some new light on in-depth understanding cathodic electrocatalysis and exploiting prominent electrocatalysts.

Characterization and manipulation of the photosystem II-semiconductor interfacial molecular interactions in solar-to-chemical energy conversion

Min He, Wangyin Wang, Zheyi Liu, Wenxiang Zhang, Jinan Li, Wenming Tian, Ye Zhou, Yan Jin, Fangjun Wang, Can Li

2022, 70(7): 437-443. DOI: 10.1016/j.jechem.2022.03.002

Abstract ( 9 )

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Semi-artiﬁcial photosynthesis interfacing catalytic protein machinery with synthetic photocatalysts exhi-bits great potential in solar-to-chemical energy conversion. However, characterizing and manipulating the molecular integration structure at the biotic-abiotic interface remain a challenging task. Herein, the biointerface molecular integration details of photosystem II (PSII)-semiconductor hybrids, including the PSII orientation, interfacial microdomains, and overall structure modulation, are systematically inter- rogated by lysine reactivity proﬁling mass spectrometry. We demonstrate the semiconductor surface bio- compatibility is essential to the PSII self-assembly with uniform orientation and electroactive structure. Highly directional localization of PSII onto more hydrophilic Ru/SrTiO3:Rh surface exhibits less distur- bance on PSII structure and electron transfer chain, beneﬁcial to the high water splitting activity. Further, rational modiﬁcation of hydrophobic Ru2S3/CdS surface with biocompatible protamine can improve the hybrid O2-evolving activity 83.3%. Our results provide the mechanistic understanding to the structure-activity relationship of PSII-semiconductor hybrids and contribute to their rational design in the future.

Transition metal-based single-atom catalysts (TM-SACs); rising materials for electrochemical CO₂reduction

Bishnupad Mohanty, Suddhasatwa Basu, Bikash Kumar Jena

2022, 70(7): 444-471. DOI: 10.1016/j.jechem.2022.02.045

Abstract ( 9 )

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The continuous increase of global atmospheric CO₂ concentrations brutally damages our environment. A series of methods have been developed to convert CO₂ to valuable fuels and value-added chemicals to maintain the equilibrium of carbon cycles. The electrochemical CO₂ reduction reaction (CO₂RR) is one of the promising methods to produce fuels and chemicals, and it could offer sustainable paths to decrease carbon intensity and support renewable energy. Thus, significant research efforts and highly efficient catalysts are essential for converting CO₂ into other valuable chemicals and fuels. Transition metal-based single atoms catalysts (TM-SACs) have recently received much attention and offer outstanding electrochemical applications with high activity and selectivity opportunities. By taking advantage of both heterogeneous and homogeneous catalysts, TM-SACs are the new rising star for electrochemical conversion of CO₂ to the value-added product with high selectivity. In recent years, enormous research effort has been made to synthesize different TM-SACs with different M-N_x sites and study the electrochemical conversion of CO₂ to CO. This review has discussed the development and characterization of different TM-SACs with various catalytic sites, fundamental understanding of the electrochemical process in CO₂RR, intrinsic catalytic activity, and molecular strategics of SACs responsible for CO₂RR. Furthermore, we extensively review previous studies on 1st-row transition metals TM-SACs (Ni, Co, Fe, Cu, Zn, Sn) and dual-atom catalysts (DACs) utilized for electrochemical CO₂ conversions and highlight the opportunities and challenges.

La-doped NiFe-LDH coupled with hierarchical vertically aligned MXene frameworks for efﬁcient overall water splitting

Mengzhou Yu, Jiqi Zheng, Ming Guo

2022, 70(7): 472-479. DOI: 10.1016/j.jechem.2022.02.044

Abstract ( 30 )

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The development of stable electrocatalysts with high hydrogen and oxygen evolution reactions (HER and OER) activity in alkaline electrolytes is critical to renewable energy conversion technologies, such as electrochemical water splitting. In this work, a novel strategy for engineering water splitting electrocatalysts in alkaline electrolyte was developed by synergistically coupling La-doped NiFe-layered double hydroxides (NiFe-LDH) nanosheets onto three-dimensional (3D) vertically aligned MXene nanosheets on macroporous nickel foam (NF) substrates (NiFeLa-LDH/v-MXene/NF). The electrocatalytic performance of the prepared NiFeLa-LDH/v-MXene/NF is enhanced by the synergy of strong electronic interaction among multiple metal centers and unique vertically aligned porous MXene with increased active surface area, accelerated reaction kinetics and improved water adsorption and dissociation ability. To reach the commercially required current density (500 mA cm^-2), the NiFeLa-LDH/v-MXene/NF exhibits greatly reduced overpotentials of 233 and 255 mV for HER and OER, respectively, along with excellent durability. Moreover, an alkaline electrolyzer driven by NiFeLa-LDH/v-MXene/NF delivers a lower cell voltage (1.71 V) compared with that of Pt/C-RuO₂ couple to achieve the current density of 500 mA cm^-2.

Zinc-ion hybrid supercapacitors with ultrahigh areal and gravimetric energy densities and long cycling life

Ahmad Amiri, M. Naraghi, Andreas A. Polycarpou

2022, 70(7): 480-491. DOI: 10.1016/j.jechem.2022.03.029

Abstract ( 6 )

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Zinc ion hybrid supercapacitor (ZIHSC) with promising energy and power densities is an excellent answer to the ever-growing demand for energy storage devices. The restricted lifespan due to the dendrite formation on metallic zinc (Zn) is one of the main roadblocks. Herein, we investigate the electrochemical capability of oxygen-enriched porous carbon nanofibers (A-CNF) and nitrogen, oxygen-enriched porous carbon nanofibers (N-CNF) cathode materials for structural ZIHSCs. To this end, a series of samples with different chemical compositions (N and O contents) are prepared to present deep insight into the electrochemical mechanism between N/O doping and Zn-ion storage. The as-prepared ZIHSC in the presence of N-CNF cathode and ZnCl₂ electrolyte offers a battery-level gravimetric energy density of 143.2 Wh kg^-1 at a power density of 367.1 W kg^-1. The free-standing N-CNF electrodes in ZIHSCs enjoy delivering an outstanding areal energy density of 110.4 µWh cm^-2 at 0.24 mW cm^-2, excellent rate capability, and noticeable cycling stability over 10,000 cycles at 10 A g^-1 with less than 7% decay. It was also concluded that active pyrrolic N dopants might deliver and facilitate more pseudocapacitance in ZIHSCs than other N configurations,resulting in higher adsorption/ desorption and insertion/extraction process of ZnCl⁺. Taking advantage of the beneficial properties of a free-standing continuous cathode, this novel generation of structural cathode material offers high areal and gravimetric energy densities and mechanical properties in a single zinc-ion-based package.

Synergistic effects of chloride anions and carboxylated cellulose nanocrystals on the assembly of thick three-dimensional high-performance polypyrrole-based electrodes

Zuxin Sun, Samuel Eyley, Yongjian Guo, Reeta Salminen, Wim Thielemans

2022, 70(7): 492-501. DOI: 10.1016/j.jechem.2022.03.004

Abstract ( 8 )

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Porous three-dimensional (3D) structures generally improve the performance of electrodes by increasing their active surface area and the diffusion speed of electrolyte ions during charging/discharging. Three-dimensional polypyrrole (PPy) based films were created by electrodepositing PPy in the presence of varying amounts of chloride anions (Cl^-) and polyanionic ribbonlike nanoparticles (carboxylated cellulose nanocrystals (CNC-COO^-)) as scaffold material. The assembly mechanism of the 3D PPy electrodes combines the effect of different nucleation and growth mechanisms during electropolymerization and deposition of the formed PPy with CNC-COO^- and with Cl^-. The highest area capacitance of these electrode materials was 1.39 F cm^-2 (150.2 F g^-1) at a current density of 1 mA cm^-2 (0.1 A g^-1). More importantly, at a high current density of 20 mA cm^-2 (2.2 A g^-1), the thick (ca. 130 μm), 3D, and high mass loading (9.2 mg cm^-2) Cl^-:CNC-COO^-/PPy films exhibited an excellent areal capacitance of 0.85 F cm^-2 (70.8 F g^-1), increasing about 16% over CNC-COO^-/PPy films prepared without Cl^- present during electrodeposition. In addition, an aqueous Cl^-:CNC-COO^-/PPy (with Cl^-:CNC-COO^- = 2.0) symmetric supercapacitor had an outstanding energy density of 41.15 μWh cm^-2 (4.46 Wh kg^-1) and excellent cycling stability, while even improving on its original areal capacitance (to 111.2% of its original capacitance) after cycling 3000 cycles at 8 mA cm^-2, indicating their potential in energy storage devices.

Notes in accordions—organized MXene equipped with CeO₂for synergistically adsorbing and catalyzing polysulﬁdes for high-performance lithium-sulfur batteries

Xiaochuan Chen, Libo Li, Yuhang Shan, Da Zhou, Wenjun Cui, Yangmingyue Zhao

2022, 70(7): 502-510. DOI: 10.1016/j.jechem.2022.02.046

Abstract ( 11 )

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：Limited by the shuttle effect, the application of lithium-sulfur batteries is not impressive. As an organ layered two-dimensional (2D) material, MXene has a great electrical conductivity and high specific surface area. Meanwhile, the introduction of metal oxides can restrain the shuttle effect. Hence, this paper prepared CeO₂/MXene as a cathode material of Li-S batteries. Ce and Ti can chemically adsorb S, and the interlayer structure of MXene can limit S while the interlayer space can alleviate volume expansion. The discharge capacity at 0.5 C is as high as 1051.1 mAh g^-1, and 921.9 mAh g^-1 after 200 cycles. The average coulombic efficiency is 97.75%. The organized MXene with CeO₂ like notes in accordions are new efficient materials for lithium-sulfur batteries.

Inﬂuence of different Fe doping strategies on modulating active sites and oxygen reduction reaction performance of Fe, N-doped carbonaceous catalysts

Yang Liu, Suqiong He, Bing Huang, Ziyan Kong, Lunhui Guan

2022, 70(7): 511-520. DOI: 10.1016/j.jechem.2022.03.005

Abstract ( 15 )

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Fe/N/C catalysts, synthesized through the pyrolysis of Fe-doped metal-organic framework (MOF) precursors, have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries. However, post-treatments (acid washing, second pyrolysis, and so on) are unavoidable to improve ORR catalytic activity and stability. The method for introducing Fe³⁺ sources (anhydrous FeCl₃) into the MOF structure, in particular, is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_x active sites. Herein, three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance. Fe-NC(Zn²⁺), synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn²⁺) precursor which was obtained by adding the anhydrous FeCl₃ source into the Zn(NO₃)₂•6H₂O/methanol solution before mixing, possessed the highest Fe-N_x active sites due to the high-efficiency substitution of Zn²⁺ ions with Fe³⁺ ions during ZIF-8 growth, the strong interaction between Fe³⁺ ions and N atoms of 2-Methylimidazole (2-MIm), and ZIF-8′s micropore confinement effect. As a result, Fe-NC(Zn²⁺) presented high ORR activity in the entire pH range (pH = 1, 7, and 13). At pH = 13, Fe-NC(Zn²⁺) exhibited a half-wave potential (E_1/2) of 0.95 V (vs. reversible hydrogen electrode), which was 70 mV higher than that of commercial Pt/C. More importantly, Fe-NC(Zn²⁺) showed superior ORR stability in neutral media without performance loss after 5,000 cycles. A record-high open-circuit voltage (1.9 V) was obtained when Fe-NC(Zn²⁺) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media. The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn²⁺) has enormous potential for use in flexible and wearable Mg-air batteries.

Boosting energy-storage capability in carbon-based supercapacitors using low-temperature water-in-salt electrolytes

João Pedro A. Santos, Manuel J. Pinzón, Érick A. Santos, Rafael Vicentini, Cesar J.B. Pagan, Leonardo M. Da Silva, Hudson Zanin

2022, 70(7): 521-530. DOI: 10.1016/j.jechem.2022.02.055

Abstract ( 11 )

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Supercapacitors (SCs) are high-power energy storage devices with ultra-fast charge/discharge properties. SCs using concentrated aqueous-based electrolytes can work at low temperatures due to their intrinsic properties, such as higher freezing point depression (FPD) and robustness. Besides the traditional organic- and aqueous-based (salt-in-water) electrolytes used in SCs, water-in-salt (WISE) sodium perchlorate electrolytes offer high FPD, non-flammability, and low-toxicity conditions, allowing the fabrication of safer, environmentally friendly, and more robust devices. For the first time, this work reports a comprehensive study regarding WISE system's charge-storage capabilities and physicochemical properties under low-temperature conditions (T < 0 °C) using mesoporous carbon-based electrodes. The effect of temperature reduction on the electrolyte viscosity and electrical properties was investigated using different techniques and the in-situ (or operando) Raman spectroscopy under dynamic polarization conditions. The cell voltage, equivalent series resistance, and specific capacitance were investigated as a function of the temperature. The cell voltage (U) increased ∼ 50%, while the specific capacitance decreased ∼ 20% when the temperature was reduced from 25 °C to -10 °C. As a result, the maximum specific energy (E = CU²/2) increased ∼ 100%. Therefore, low-temperature WISEs are promising candidates to improve the energy-storage characteristics in SCs.

Inﬂuences of multi factors on thermal runaway induced by overcharging of lithium-ion battery

Jialong Liu, Zhirong Wang, Jinlong Bai

2022, 70(7): 531-541. DOI: 10.1016/j.jechem.2022.03.011

Abstract ( 16 )

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Thermal runaway caused by overcharging results in catastrophic disasters. The influences of charging rate, ambient temperature and aging on thermal runaway caused by overcharging are studied qualitatively and quantitatively in this manuscript. The results of overcharging tests indicate that high charging rate and ambient temperature increase thermal runaway risk. Aging in 40 °C decreases thermal runaway risk. The risk increase of battery with high overcharging rate and in high ambient temperature is due to fast lithium plating reaction and accelerated SEI decomposition, respectively. The risk decrease of aged battery is due to the occurrence of SEI before overcharging tests. SEI suppresses the side reactions between lithium plating and electrolyte. The results of orthogonal tests indicate that the rank of effect is: discharging rate > ambient temperature > aging. The heat generation is calculated based on the results of overcharging tests. The calculation results indicate that heat generated by side reactions contributes more to the total heat generation. Although thermal runaway does not occur during overcharging with low current, the heat dissipation of the lithium-ion battery is the most and deserves focus. The results are important to the design of battery management system and thermal management system to prevent thermal runaway induced by overcharging in total lifespan of battery.

Recent developments in electrosynthesis of nitriles and electrocatalytic cyanations

Haiyan Hu, Shanxuan Wu, Fachao Yan, Mohamed Makha, Yuxia Sun, Chen-Xia Du, Yuehui Li

2022, 70(7): 542-575. DOI: 10.1016/j.jechem.2022.02.054

Abstract ( 12 )

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The cost-effective organic semiconductors are strongly needed in organic photovoltaics (OPVs). Herein, two medium bandgap (MBG) electron acceptors, TPT4F and TPT4Cl are developed via the new design of multi-noncovalent interaction assisted unfused core, flanked with two electron withdrawing end groups. These fullly non-fused MBG acceptors adapt the planar and rigid conformation in solid, therefore exhibiting the ordered face-on stacking and strong photoluminescence in films. As results, TPT4Cl-based OPVs, upon blending with the PBDB-TF polymer donor, have achieved a power conversion efficiency of 10.16% with a low non-radiative loss of 0.27 eV, representing one of the best fullly non-fused medium bandgap acceptors with desirable cost-efficiency balance.

Non-fused medium bandgap electron acceptors for efﬁcient organic photovoltaics

Tian-Jiao Wen, Jiale Xiang, Nakul Jain, Zhi-Xi Liu, Zeng Chen, Xinxin Xia, Xinhui Lu, Haiming Zhu, Feng Gao, Chang-Zhi Li

2022, 70(7): 576-582. DOI: 10.1016/j.jechem.2022.03.030

Abstract ( 8 )

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Nitrile compounds are a class of high-value chemicals and versatile intermediates which can easily be transformed into a variety of useful products bearing functional groups such as carboxyl, carbamoyl, aminomethyl, ketyl and heterocyclic derivatives. Various thermal catalytic cyanation procedures have been devised and scaled up industrially while developing alternative methods are actively pursued. The access to these classes of molecules electrochemically offers greener alternatives to their preparation. The development of electrochemical synthesis of cyano-containing compounds under mild conditions with low energy consumption will imminently become indispensable approaches for industrial production of nitriles. The electrochemical cyanation presents many challenges from the toxicity of cyanide to the development of catalysts and the design of electrochemical cells. Electrochemical cyanation reaction offers promise to conveniently accessing nitriles but still requires efficient electro-catalysts, safe protocols and scale up considerations. This review discusses recent progress in the field of electrochemical synthesis of nitrile compounds placing emphasis on electro-synthetic and electro-catalytic mechanism aspects while making reference to original works to highlight the progress in this area.

Ex situ aging effect on sulfonated poly(ether ether ketone) membrane:Hydration-dehydration cycling and hydrothermal treatment

Seung-Young Choi, Kyeong Sik Jin

2022, 70(7): 583-592. DOI: 10.1016/j.jechem.2022.03.003

Abstract ( 10 )

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Prolonged hydrothermal treatment for sulfonated poly(ether ether ketone) membranes induces mechanical degradation and developing hydrophilic-hydrophobic phase separation, simultaneously. The enhanced phase separation provides incremental proton conductivity to the membranes, whereas mechanical degradation drastically reduces device stability. On this basis, we describe here the effects of two different ex situ aging processes on sulfonated poly(ether ether ketone) membranes: hydration-dehydration cycling and prolonged hydrothermal treatment. Both aged membranes exhibited enhanced phase separation under the hydrated conditions, as characterized by small angle X-ray scattering. However, when the aged membranes were dried again, the nanostructure of the membranes aged via the hydration-dehydration cycling was recoverable, whereas that of the membranes aged via prolonged hydrothermal treatment was irreversible. Furthermore, the two differently aged membranes showed clear differences in thermal, mechanical, and electrochemical properties. Finally, we implemented both aged membranes in fuel cell application. The sample aged via hydration-dehydration cycling maintained its improved cell performance, whereas the sample aged via hydrothermal treatment showed drastically reduced cell performance after durability test for 50 h.

A hollow tubular NiCo layacknered double hydroxide@Ag nanowire structure for high-power-density ﬂexible aqueous Ni//Zn battery

Xiaoyang Xuan, Min Qian, Likun Pan, Ting Lu, Yang Gao, Lu Han, Lijia Wan, Yueping Niu, Shangqing Gong

2022, 70(7): 593-603. DOI: 10.1016/j.jechem.2021.12.013

Abstract ( 10 )

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Flexible aqueous Ni//Zn batteries have attracted much attention as promising candidates for energy storage in the field of flexible electronics. However, the Ni-based cathodes still face the challenges of poor conductivity, confined charge/mass transfer, and non-flexibility. In this work, we designed a hollow tubular structure consisting of a conductive silver nanowire (AgNW) wrapped by active NiCo layered double hydroxide (LDH), for enhancing the electrical conductivity, improving the charge/mass transfer kinetics, and facilitating the ion penetration. By optimizing the contents of Ni, Co and AgNW, the Ni₄Co LDH@Ag_1.5NW composite shows a maximum specific capacity of 115.83 mAh g^-1 at 0.1 A g^-1 measured in a two-electrode system. Highlightingly, the flexible aqueous Ni//Zn battery assembled by Ni₄Co LDH@Ag_1.5NW interwoven with multi-walled carbon nanotube cathode and Zn foil anode realizes a high power density of 160 μW cm^-2 at the energy density of 23.14 μWh cm^-2, which is superior compared with those of oxide/hydroxide based devices and even higher than those of many carbon-based supercapacitors, showing its promising potentials for flexible energy storage applications.

Multiple transition metals modulated hierarchical networks for high performance of metal-ion batteries

Jie Liu, Chenjie Lou, Jipeng Fu, Xuan Sun, Jingrong Hou, Jiwei Ma, Yongjin Chen, Xiang Gao, Ligang Xu, Qi Wei, Mingxue Tang

2022, 70(7): 604-613. DOI: 10.1016/j.jechem.2022.02.053

Abstract ( 8 )

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Searching anodes with excellent electrochemical performance has been in great demand for rechargeable metal ion batteries. In this contribution, Fe/Co co-doped NiS with N-based carbon (FeCo-NiS@NC) derived from trimetallic Prussian blue analogue is designed and synthesized. The composition can be easily adjusted and modulated by multi-metals. In addition, the well-designed carbon nanocubes effectively promote electronic conductivity and buffer the volume change upon charge and discharge cycling, resulting in good capacity and long-term cycle life for both lithium-ion batteries and sodium-ion batteries, with capacities of 1018 mAh g^-1 (vs. Li/Li⁺) and 454 mAh g^-1 (vs. Na/Na⁺), respectively, after 100 cycles. Kinetics studies indicate that the electrochemical behaviors are manipulated by both diffusion and pseudocapacitance processes. These strategies would open new opportunities and potention for novel energy storage.

Tuning the nucleation and decomposition of Li₂O₂by ﬂuorine-doped carbon vesicles towards high performance Li-O₂batteries

Shiyu Ma, Hongchang Yao, Zhongjun Li, Qingchao Liu

2022, 70(7): 614-622. DOI: 10.1016/j.jechem.2022.03.007

Abstract ( 9 )

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Li-O₂ batteries provide an attractive and potential strategy for energy conversion and storage with high specific energy densities. However, large over-potential in oxygen evolution reactions (OER) caused by the decomposition obstacles of Li₂O2 seriously impedes its electrochemical performances. Herein, a novel N, O, S and F co-doping vesicular carbon was prepared by self-template pyrolysis method and used in Li-O2 battery to tune the nucleation and decomposition of Li2O2. The introduction of F in the carbon matrix with suitable content can regulate the adsorption of intermediates, through which the morphology of Li₂O2 can be controlled to film, favorable to its decomposition in charge process. The cathode based on the optimized F doped carbon vesicle exhibits improved electrochemical performances including a low over-potential, large capacity and a long-term stability. Density functional theory (DFT) results show that F and C in C–F bond hasve a strong interaction to Li and O in Li₂O2, respectively, which can enhance the transfer of electrons from Li₂O2 to the carbon matrix to generate hole polaron and thus accelerate the delithiation and decomposition of Li₂O2. This work provides a new sight into understanding the mechanism of nucleation and decomposition of Li₂O2 for the development of high-performance Li-O₂ batteries.

Mixed B-site ruddlesden-popper phase Sr₂(Ru_xIr_1-x)O₄enables enhanced activity for oxygen evolution reaction

Fangfang Wang, Cheng Zhang, Hong Yang

2022, 70(7): 623-629. DOI: 10.1016/j.jechem.2022.02.051

Abstract ( 5 )

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Development of high performance electrocatalysts for oxygen evolution reaction (OER) in acidic media remains a challenge for direct water splitting using an electrolyzer. Recently, Ruddlesden-Popper phase Sr₂IrO₄ was discovered to be an efficient OER catalyst because of its unique structure, which consists of layers of both rock salt and perovskite phases simultaneously. In this study, we prepared a series of B-site mixed, Ruddlesden-Popper phase of Sr₂(Ru_xIr_1-_x)O₄ and examined their electrocatalytic properties for OER in acidic media. Through partial substitution of Ru in the B-site of Ruddlesden-Popper phase materials, we achieved much enhanced OER performance for this series of Sr₂(Ru_xIr_1-_x)O₄ electrocatalysts, among which Sr₂(Ru_0.5Ir_0.5)O₄ exhibited the best catalytic activity with a current density of 8.06 mA/cm² at 1.55 V and a Tafel slope of 47 mV/dec. This current density is three times higher than that of Sr₂IrO₄. The B-site mixed Sr₂(Ru_0.5Ir_0.5)O₄ retained good stability in acidic conditions for > 24 h at 10 mA/cm². A range of techniques were used to characterize the crystal and electronic structures of the Sr₂(Ru_xIr_1-_x)O₄ samples. Our data indicate that the improved OER performance can be correlated to the formation of high level of hydroxyl groups and the enhanced overlap between Ir/Ru 4d and O 2p orbitals, revealing a new way for the design of efficient OER electrocatalysts by regulating their composition and electronic structures.

Nanotube-based heterostructures for electrochemistry: A mini-review on lithium storage, hydrogen evolution and beyond

Yongjia Zheng, Wanyu Dai, Xue-Qiang Zhang, Jia-Qi Huang, Shigeo Maruyama, Hong Yuan, Rong Xiang

2022, 70(7): 630-642. DOI: 10.1016/j.jechem.2022.02.029

Abstract ( 7 )

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Nanotube-based mixed-dimensional or one-dimensional heterostructures have attracted great attention recently because of their unique physical properties and therefore potential for novel devices. Their chemical properties, however, were less explored but can be utilized for energy storage and conversion. In this review, we summarize the recent progress of nanotube-based low dimensional materials for electrochemistry, in particular, lithium storage and hydrogen evolution. First, we describe the atomic structure of low-dimensional heterostructures and briefly touch previous work on planar van der Waals heterostructures (2D + 2D) in electrochemistry applications. Then we focus this review on the more recently developed nanotube-based, i.e., 1D + 2D and 1D + 1D heterostructures, and discuss their various preparation approaches and electrochemical performances. Finally, we outline the challenges and opportunities in this direction and particularly emphasize the possibility of building high-performance electrodes using a single-walled carbon nanotube-based ultra-thin 1D heterostructure, and the importance of understanding the fundamental mechanism at atomic precision.

Wettability control in electrocatalyst: A mini review

Yan Liang, Yifeng Han, Jing-sha Li, Jun Wang, Depei Liu, Qi Fan

2022, 70(7): 643-655. DOI: 10.1016/j.jechem.2021.09.005

Abstract ( 16 )

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Electrocatalysis, as a typical heterogeneous catalysis, generally occurs in the di- or tri-phase interfaces. Wettability is an important property for describing the balance of a gas-liquid-solid system. Therefore, the wettability of reaction interface, especially hydrophilicity/hydrophobicity, plays an important role in the adsorption/desorption process of gas bubbles on the surface of the solid electrode. Herein, we present a comprehensive review of the wettability control of the electrode materials applied in electrocatalysis reactions, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and carbon dioxide reduction reaction (CO₂RR). Firstly, the basic theories of wettability as well as the impact on electrocatalysis were introduced in this review. Secondly, the overview of modifying methods of the wettability from electrocatalyst microstructure (structural modification, surface coating, introducing hydrophilic groups) and system design (electrode, device) were suggested. At last, the deficiencies and problems in the application of wettability control are discussed, and deeper and broader application prospects are proposed.

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