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2022, Vol. 64, No. 1　Online: 15 January 2022

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Operando HERFD-XANES and surface sensitive Δμ analyses identify the structural evolution of copper(II) phthalocyanine for electroreduction of CO2 Bingbao Mei, Cong Liu, Ji Li, Songqi Gu, Xianlong Du, Siyu Lu, Fei Song, Weilin Xu, Zheng Jiang 2022, 64(1): 1-7.  DOI: 10.1016/j.jechem.2021.04.049 Abstract ( 19 )   PDF (3340KB) ( 5 )   The quantitative understanding of how atomic-level catalyst structural changes affect the reactivity of the electrochemical CO2 reduction reaction is challenging. Due to the complexity of catalytic systems, conventional in situ X-ray spectroscopy plays a limited role in tracing the underlying dynamic structural changes in catalysts active sites. Herein, operando high-energy resolution fluorescence-detected X-ray absorption spectroscopy was used to precisely identify the dynamic structural transformation of well-defined active sites of a representative model copper (II) phthalocyanine catalyst which is of guiding sig-nificance in studying single-atom catalysis system. Comprehensive X-ray spectroscopy analyses, includ-ing surface sensitive Dl spectra which isolates the surface changes by subtracting the disturb of bulk base and X-ray absorption near-edge structure spectroscopy simulation, were used to discover that Cu species aggregated with increasing applied potential, which is responsible for the observed evolution of C2H4. The approach developed in this work, characterizing the active-site geometry and dynamic struc-tural change, is a novel and powerful technique to elucidate complex catalytic mechanisms and is expected to contribute to the rational design of highly effective catalysts.

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Post-treatment by an ionic tetrabutylammonium hexafluorophosphate for improved efficiency and stability of perovskite solar cells Chaoqun Zhang, Xiaodong Ren, Xilai He, Yunxia Zhang, Yucheng Liu, Jiangshan Feng, Fei Gao, Ningyi Yuan, Jianning Ding, Shengzhong(Frank)Liu 2022, 64(1): 8-15.  DOI: 10.1016/j.jechem.2021.04.058 Abstract ( 11 )   PDF (4213KB) ( 2 )   Interface engineering is an effective way to improve efficiency and long-term stability of perovskite solar cells (PSCs). Herein, an ionic compound tetrabutylammonium hexafluorophosphate (TP6) is adopted to passivate surface defects of the perovskite film. It is found that TP6 effectively reduced the surface defects, especially at the grain boundaries where the defects are abundant. Meanwhile, the exposed long alkyl chains and fluorine atoms in the TP6 enhanced the moisture stability of the perovskite film due to its strong hydrophobicity. In addition, the driving force of charge carrier separation and transport is increased by enlarged built-in potential. Consequently, the power conversion efficiency (PCE) of PSCs is significantly improved from 20.59% to 22.41% by increased open-circuit voltage (Voc) and fill factor (FF). The unencapsulated device with TP6 treatment exhibits better stability than the control device, and the PCE retains ~ 80% of its initial PCE after 30 days under 15%-25% relative humidity in storage, while the PCE of the control device declines by more than 50%.

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Interface-enhanced thermoelectric output power in CrN/SrTiO3-x heterostructure Xueying Wan, Xiaowei Lu, Lin Sun, Mingyu Chen, Na Ta, Wei Liu, Qi Chen, Liwei Chen, Jian He, Peng Jiang, Xinhe Bao 2022, 64(1): 16-22.  DOI: 10.1016/j.jechem.2021.04.056 Abstract ( 11 )   PDF (5970KB) ( 2 )   Thermoelectric devices enable direct conversion between thermal and electrical energy. Recent studies have indicated that the thin film/substrate heterostructure is effective in achieving high thermoelectric performance via decoupling the Seebeck coefficient and electrical conductivity otherwise adversely inter-dependent in homogenous bulk materials. However, the mechanism underlying the thin film/sub-strate heterostructure thermoelectricity remains unclear. In addition, the power output of the thin film/-substrate heterostructure is limited to the nanowatt scale to date, falling short of the practical application requirement. Here, we fabricated the CrN/SrTiO3-x heterostructures with high thermoelectric output power and outstanding thermal stability. By varying the CrN film thickness and the reduction degree of SrTiO3-x substrate, the optimized power output and the power density have respectively reached 276 lW and 108 mW/cm2 for the 30 nm CrN film on a highly reduced surface of SrTiO3-x under a tem-perature difference of 300 K. The performance enhancement is attributed to the CrN/SrTiO3-x heteroin-terface, corroborated by the band bending as revealed by the scanning Kelvin probe microscopy. These results will stimulate further research efforts towards interface thermoelectrics.

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MnO2 cathode materials with the improved stability via nitrogen doping for aqueous zinc-ion batteries Yanan Zhang, Yanpeng Liu, Zhenhua Liu, Xiaogang Wu, Yuxiang Wen, Hangda Chen, Xia Ni, Guohan Liu, Juanjuan Huang, Shanglong Peng 2022, 64(1): 23-32.  DOI: 10.1016/j.jechem.2021.04.046 Abstract ( 17 )   PDF (7923KB) ( 3 )   The research and exploration of manganese-based aqueous zinc-ion batteries have been controversial of cycle stability and mechanism investigation, thus improving the stability and exploring storage mechanism are still the most main issue. Defect engineering has become an effective method to improve cycle stability. Herein, a nitrogen-doped e-MnO2 (MnO2@N) has been prepared using electrochemical deposi-tion and heat treatment under nitrogen atmosphere. As the cathode for zinc-ion batteries, the capacityretention rate of MnO2@N cathode is close to 100% after 500 cycles at 0.5 A g-1, while the capacity reten-tion rate for the initial MnO2 cathode is 62%. At 5 A g-1, the capacity retention rate of MnO2@N cathode is 83% after 1000 cycles, which is much higher than the 27% capacity retention rate for the original MnO2 cathode. And it can be found that the oxygen vacancies increase after nitrogen doping, which can improve the conductivity of the MnO2@N cathode. Also, there is Mn-N bond in MnO2@N, which can enhance the electrochemical stability of MnO2@N cathode. In addition, the electrochemical mechanism of MnO2@N cathode has been explored by the CV, GCD and GITT tests. It is found that nitrogen doping promotes the intercalation of H+ and the corresponding capacity contribution. Compared with the original MnO2 cathode, the diffusion coefficient of H+ and Zn2+in MnO2@N cathode increases. Also, the reactions during the charging and discharging process are explored through the ex-situ XRD test. And this work may pro-vide some new ideas for improving the stability of manganese-based zinc-ion batteries.

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Unravelling the essential difference between TiOx and AlOx interface layers on Ta3N5 photoanode for photoelectrochemical water oxidation Yongle Zhao, Huichen Xie, Wenwen Shi, Hong Wang, Chenyi Shao, Can Li 2022, 64(1): 33-37.  DOI: 10.1016/j.jechem.2021.04.042 Abstract ( 12 )   PDF (4294KB) ( 2 )   Tantalum nitride (Ta3N5) is a very promising photoanode material due to its narrow band gap (2.1 eV) and suitable band alignment for solar water splitting. However, it suffers from severe photocorrosion during water oxidation. In this work, it was found that surface passivation by AlOx and TiOx layers results in dramatically different PEC performance of Ta3N5 photoanode for water oxidation. The mechanism study indicates that the negative charges on AlOx can generate additional field to promote separation of photogenerated charges, while the positive charges on TiOx layer show the opposite effect. As a result, the Ta3N5 based photoanode modified with AlOx layer gives a high photocurrent of 12.5 mA cm-2 for 24 h at 1.23 V versus the reversible hydrogen electrode (RHE). Dynamic analysis implies that the hole extrac-tion and transfer are significantly improved by the modification with the AlOx layer. This work reveals the importance of the charges on surface passivation layer in interface engineering of photoelectrodes.

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Tuned selectivity and enhanced activity of CO2 methanation over Ru catalysts by modified metal-carbonate interfaces Qiaojuan Wang, Yating Gao, Chantsalmaa Tumurbaatar, Tungalagtamir Bold, Fei Wei, Yihu Dai, Yanhui Yang 2022, 64(1): 38-46.  DOI: 10.1016/j.jechem.2021.04.039 Abstract ( 7 )   PDF (4809KB) ( 2 )   Carbonate-modified metal-support interfaces allow Ru/MnCO3 catalyst to exhibit over 99% selectivity, great specific activity and long-term anti-CO poisoning stability in atmospheric CO2 methanation. As a contrast, Ru/MnO catalyst with metal-oxide interfaces prefers reverse water-gas shift rather than metha-nation route, along with a remarkably lower activity and a less than 15% CH4 selectivity. The carbonate-modified interfaces are found to stabilize the Ru species and activate CO2 and H2 molecules. Ru-CO* spe-cies are identified as the reaction intermediates steadily formed from CO2 dissociation, which show mod-erate adsorption strength and high reactivity in further hydrogenation to CH4. Furthermore, carbonates of Ru/MnCO3 are found to be consumed by hydrogenation to form CH4 and replenished by exchange with CO2, which are in a dynamic equilibrium during the reaction. Modification with surface carbonates is proved as an efficient strategy to endow metal-support interfaces of Ru-based catalysts with unique cat-alytic functions for selective CO2 hydrogenation.

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Trace water triggers high-efficiency photocatalytic hydrogen peroxide production Zaixiang Xu, Yang Li, Yongyong Cao, Renfeng Du, Zhikang Bao, Shijie Zhang, Fangjun Shao, Wenkai Ji, Jun Yang, Guilin Zhuang, Shengwei Deng, Zhongzhe Wei, Zihao Yao, Xing Zhong, Jianguo Wang 2022, 64(1): 47-54.  DOI: 10.1016/j.jechem.2021.03.055 Abstract ( 8 )   PDF (3229KB) ( 8 )   Photocatalytic production of hydrogen peroxide (H2O2) has attracted much attentions as a promising method for sustainable solar fuel. Here, we demonstrate that trace water can drastically boost high-efficiency photocatalytic production of H2O2 with a record-high concentration of 113 mmol L-1 using alkali-assisted C3N4 as photocatalyst in water/alcohol mixture solvents. By electron paramagnetic reso-nance (EPR) measurement, the radical species generated during the photocatalytic process of H2O2 are identified. We propose alcohol is used to provide and stabilize ·OOH radicals through hydrogen bond, while trace water could trigger photocatalytic production of H2O2 via providing and transferring indis-pensable free protons to completely consume ·OOH radicals, which breaks the reaction balance of·OOH radical generation from alcohol. Thus ·OOH radicals could be supplied by alcohol continuously to serve as a reservoir for high-efficiency production of H2O2. These results pave the way towards photocat-alytic method on semiconductor catalysts as an outstanding approach for production of hydrogen peroxide.

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Passivation agent with dipole moment for surface modification towards efficient and stable perovskite solar cells Ge Wang, Chen Wang, Yajun Gao, Shanpeng Wen, Roderick C.I.MacKenzie, Liuxing Guo, Wei Dong, Shengping Ruan 2022, 64(1): 55-61.  DOI: 10.1016/j.jechem.2021.04.023 Abstract ( 10 )   PDF (5484KB) ( 2 )   Recently, there has been renewed interest in interface engineering as a means to further push the perfor-mance of perovskite solar cells closer to the Schockly-Queisser limit. Herein, for the first time we employ a multi-functional 4-chlorobenzoic acid to produce a self-assembled monolayer on a perovskite surface. With this interlayer we observe passivation of perovskite surface defects and a significant suppression of non-radiative charge recombination. Furthermore, at the surface of the interlayer we observe, charge dipoles which tune the energy level alignment, enabling a larger energetic driving force for hole extrac-tion. The perovskite surface becomes more hydrophilic due to the presence of the interlayer. Consequently, we observe an improvement in open-circuit voltage from 1.08 to 1.16 V, a power conver-sion efficiency improvement from 18% to 21% and an improved stability under ambient conditions. Our work highlights the potential of SAMs to engineer the photo-electronic properties and stability of per-ovskite interfaces to achieve high-performance light harvesting devices.

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Advances and prospects of PVDF based polymer electrolytes Yixin Wu, Yu Li, Yang Wang, Qian Liu, Qingguo Chen, Minghua Chen 2022, 64(1): 62-84.  DOI: 10.1016/j.jechem.2021.04.007 Abstract ( 17 )   PDF (23101KB) ( 9 )   Exploring highly foldable batteries with no safety hazard is a crucial task for the realization of portable, wearable, and implantable electric devices. Given these concerns, developing solid-state batteries is one of the most promising routes to achieve this aspiration. Because of the excellent flexibility and process-ability, polyvinylidene fluoride (PVDF) based electrolytes possess great potential to pack high energy den-sity flexible batteries, however, suffers the various intrinsic shortcomings such as inferior ionic conductivity, a high degree of crystallinity, and lack of reactive groups. Clearing the progress of the pre-sent state and concluding the specific challenges faced by PVDF based electrolytes will help to develop PVDF based polymer batteries. In this review, we summarize the recent progress of gel polymer elec-trolytes and all solid polymer electrolytes based on PVDF. The ion transport mechanisms and preparation methods of PVDF based electrolytes are briefly introduced. Meanwhile, the current design principle and properties of electrolytes are highlighted and systematically discussed. Some peculiar modified strategies performed in lithium-sulfur batteries and lithium-oxygen batteries are also included. Finally, this review describes the challenges and prospects of some solid-state electrolytes to provide strategies for manufac-turing high-performance PVDF electrolytes aimed at practical application with flexible requirements.

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Construction of TiO2-covalent organic framework Z-Scheme hybrid through coordination bond for photocatalytic CO2 conversion Lei Wang, Guofang Huang, Liang Zhang, Rui Lian, Jingwei Huang, Houde She, Chunli Liu, Qizhao Wang 2022, 64(1): 85-92.  DOI: 10.1016/j.jechem.2021.04.053 Abstract ( 11 )   PDF (4036KB) ( 2 )   In this work, a covalent organic framework (COF) , which is constructed by the building blocks of [5,10,15,20-tetrakis (4-aminophenyl) porphinato]copper (II) (CuTAPP) and p-benzaldehyde, is employed to integrate with TiO2 for the purpose of establishing a Z-scheme hybrid. Within the system, isonicotinic acid performs the role of a bridge that connects the two components through a coordination bond.Further photocatalytic application reveals the hybrid framework is able to catalyze CO2 conversion under simulated solar light, resulting in CO production rate of 50.5 lmol g-1 h-1, about 9.9 and 24.5 times that of COF and pristine TiO2, respectively. The ameliorated catalytic performance owes much to the por-phyrin block acting as photosensitizer that augments the light absorbance, and the establishment of Z-scheme system between the inorganic and organic components that enhances the separation of the car-riers. In addition, the chemical bridge also ensures a steady usage and stable charge delivery in the catal-ysis. Our study sheds light on the development of versatile approaches to covalently incorporate COFs with inorganic semiconductors.

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Three-dimensionalization via control of laser-structuring parameters for high energy and high power lithium-ion battery under various operating conditions Junsu Park, Hyeongi Song, Inseok Jang, Jaepil Lee, Jeongwook Um, Seong-guk Bae, Jihun Kim, Sungho Jeong, Hyeong-Jin Kim 2022, 64(1): 93-102.  DOI: 10.1016/j.jechem.2021.04.011 Abstract ( 13 )   PDF (12136KB) ( 3 )   Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery (LIB) electrodes. In this work, the effects of laser structuring parameters (groove pitch and depth) on the fundamental characteristics of LIB electrode, such as interfacial area, internal resis-tances, material loss and electrochemical performance, are investigated. LiNi0.5Co0.2Mn0.3O2 cathodes were structured by a femtosecond laser by varying groove depth and pitch, which resulted in a material loss of 5%-14% and an increase of 140%-260% in the interfacial area between electrode surface and elec-trolyte. It is shown that the importance of groove depth and pitch on the electrochemical performance (specific capacity and areal discharge capacity) of laser-structured electrode varies with current rates. Groove pitch is more important at low current rate but groove depth is at high current rate. From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy, it is verified that the groove functions as a diffusion path for lithium ions. The ionic, electronic, and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity, ionic diffusion and electronic pathways. It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.

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Visible-light deposition of CrOx cocatalyst on TiO2: Cr valence regulation for superior photocatalytic CO2 reduction to CH4 Jingjing Dong, Yuan Kong, Heng Cao, Zhiyu Wang, Zhirong Zhang, Lidong Zhang, Song Sun, Chen Gao, Xiaodi Zhu, Jun Bao 2022, 64(1): 103-112.  DOI: 10.1016/j.jechem.2021.04.028 Abstract ( 7 )   PDF (5629KB) ( 2 )   Photodeposition is widely adopted for implanting metal/metal oxide cocatalysts on semiconductors. However, it is prerequisite that the photon energy should be sufficient to excite the host semiconductor. Here, we report a lower-energy irradiation powered deposition strategy for implanting CrOx cocatalyst on TiO2. Excitingly, CrOx-400 implanted under visible-light irradiation significantly promotes the CH4 evolu-tion rate on TiO2 to 8.4 mmol g-1h-1 with selectivity of 98% from photocatalytic CO2 reduction, which is 15 times of that on CrOx-200 implanted under UV-visible-light irradiation. Moreover, CrOx-400 is identified to be composed of higher valence Cr species compared to CrOx-200. This valence states regulation of Cr species is indicated to provide more active sites for CO2 adsorption/activation and to modulate the reac-tion mechanism from single Cr site to Cr-Cr dual sites, thus endowing the superior CH4 production. This work demonstrates an alternative strategy for constructing efficient metal oxides cocatalysts on wide bandgap semiconductor.

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Controlled location of S vacancies in MoS2 nanosheets for high-performance hydrogenation of CO2 to methanol Gabriele Centi 2022, 64(1): 113-115.  DOI: 10.1016/j.jechem.2021.04.036 Abstract ( 7 )   PDF (716KB) ( 3 )

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Characteristics of a gold-doped electrode for application in high-performance lithium-sulfur battery Vittorio Marangon, Daniele Di Lecce, Dan J.L. Brett, Paul R. Shearing, Jusef Hassoun 2022, 64(1): 116-128.  DOI: 10.1016/j.jechem.2021.04.025 Abstract ( 11 )   PDF (12361KB) ( 2 )   Bulk sulfur incorporating 3 wt% gold nano-powder is investigated as possible candidate to maximize the fraction of active material in the Li-S battery cathode. The material is prepared via simple mixing of gold with molten sulfur at 120 °C, quenching at room temperature, and grinding. Our comprehensive study reports relevant electrochemical data, advanced X-ray computed tomography (CT) imaging of the posi-tive and negative electrodes, and a thorough structural and morphological characterization of the S:Au 97:3 w/w composite. This cathode exhibits high rate capability within the range from C/10 to 1C, a max-imum capacity above 1300 mAh g-S 1, and capacity retention between 85% and 91% after 100 cycles at 1C and C/3 rates. The novel formulation enables a sulfur fraction in the composite cathode film as high as 78 wt%, an active material loading of 5.7 mg cm-2, and an electrolyte/sulfur (E/S) ratio of 5 lL mg-1, which lead to a maximum areal capacity of 5.4 mAh cm-2. X-ray CT at the micro-and nanoscale reveals the microstructural features of the positive electrode that favor fast conversion kinetics in the battery. Quantitative analysis of sulfur distribution in the porous cathode displays that electrodeposition during the initial cycle may trigger an activation process in the cell leading to improved performance. Furthermore, the tomography study reveals the characteristics of the lithium anode and the cell separator upon a galvanostatic test prolonged over 300 cycles at a 2C rate.

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Binary ligand strategy toward interweaved encapsulation-nanotubes structured electrocatalyst for proton exchange membrane fuel cell Qingbin Liu, Li Xu, Shizhen Liu, Zhonghua Xiang 2022, 64(1): 129-135.  DOI: 10.1016/j.jechem.2021.04.064 Abstract ( 7 )   PDF (5583KB) ( 2 )   Hierarchically porous architecture of iron-nitrogen-carbon (Fe-N-C) for oxygen reduction reaction (ORR) is highly desired towards efficient mass transfer in the fuel cell device manner. Herein, we reported a bin-ary ligand strategy to prepare zeolitic imidazolate frameworks (ZIFs) -derived precursors, wherein the addition of secondary ligand endows precursors with the capabilities to transform into porously inter-weaved encapsulation-nanotubes structured composites after calcination. The optimal catalyst, i.e., ter-med as Fe6-M/C-3, exhibits excellent durability with 88.8% current retention after 50,000 seconds in 0.1 M HClO4 solution by virtue of nanoparticles-encapsulation features, which is more positive than the benchmark commercial 20 wt% Pt/C catalyst. Moreover, a promising maximum power density of Fe6-M/C-3 as cathode catalyst was also demonstrated in proton exchange membrane fuel cells (PEMFCs) measurements. Therefore, this binary ligand approach to the fabrication of hierarchically por-ous structures would also have significant implications for various other electrochemical reactions.

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Redox-etching induced porous carbon cloth with pseudocapacitive oxygenic groups for flexible symmetric supercapacitor Xu Han, Zi-Hang Huang, Fanjin Meng, Baohua Jia, Tianyi Ma 2022, 64(1): 136-143.  DOI: 10.1016/j.jechem.2021.04.035 Abstract ( 8 )   PDF (6941KB) ( 11 )   Constructing high-performance electrodes with both wide potential window (e.g. ≥ 2 V in aqueous elec-trolyte) and excellent mechanical flexibility represents a great challenge for supercapacitors. Because of the outstanding conductivity and flexibility, carbon cloth (CC) has shown unlimited prospects for con-structing flexible electrodes, but is rarely used directly as electrode material due to its electrochemical inertness and small specific surface area. To tackle these two critical limitations, we design a novel redox-etching strategy to synthesize CC-based electrode with 3D interconnecting pore structure. The sponge-like highly porous CC was further activated by strong oxidant to form abundant oxygenic groups, which occupy the interior and surface of current collector to render substantial pseudocapacitance. The as-synthesized CC electrode yielded an impressive capacitance of 4035 mF cm-2 at 3 mA cm-2 and sat-isfying cycling durability in a wide potential range of -1-1 V vs. SCE, which surpass the majority of reported CC-based electrodes. A symmetric supercapacitor with stable voltage of 2 V is assembled and delivers remarkable energy density of 6.57 mWh cm-3. Significantly, the device demonstrates an unpar-alleled flexibility with no capacitive decay after 100 bending cycles. This facile chemical etching and post-treatment processes are designed for large-scale manufacturing of the CC electrodes by providing high surface area and abundant electrochemically active sites, promising for industry application. The innova-tive synthetic strategy opens up new opportunities for high-performance flexible energy storage.

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Multivalent metal-sulfur batteries for green and cost-effective energy storage: Current status and challenges Yue Yang, Haoyi Yang, Xinran Wang, Ying Bai, Chuan Wu 2022, 64(1): 144-165.  DOI: 10.1016/j.jechem.2021.04.054 Abstract ( 11 )   PDF (14690KB) ( 1 )   Multivalent metal-sulfur (M-S, where M = Mg, Al, Ca, Zn, Fe, etc.) batteries offer unique opportunities to achieve high specific capacity, elemental abundancy and cost-effectiveness beyond lithium-ion batteries (LIBs). However, the slow diffusion of multivalent-metal ions and the shuttle of soluble polysulfide result in impoverished reversible capacity and limited cycle performance of M-S (Mg-S, Al-S, Ca-S, Zn-S, Fe-S, etc.) batteries. It is a necessity to optimize the electrochemical performance, while deepening the under-standing of the unique electrochemical reaction mechanism, such as the intrinsic multi-electron reaction process, polysulfides dissolution and the instability of metal anodes. To solve these problems, we have summarized the state-of-the-art progress of current M-S batteries, and sorted out the existing chal-lenges for different multivalent M-S batteries according to sulfur cathode, electrolytes, metallic anode and current collectors/separators, respectively. In this literature, we have surveyed and exemplified the strategies developed for better M-S batteries to strengthen the application of green, cost-effective and high energy density M-S batteries.

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Concurrent recycling chemistry for cathode/anode in spent graphite/LiFePO4 batteries: Designing a unique cation/anion-co-workable dual-ion battery Yun-Feng Meng, Hao-Jie Liang, Chen-De Zhao, Wen-Hao Li, Zhen-Yi Gu, Meng-Xuan Yu, Bo Zhao, Xian-Kun Hou, Xing-Long Wu 2022, 64(1): 166-171.  DOI: 10.1016/j.jechem.2021.04.047 Abstract ( 12 )   PDF (2463KB) ( 9 )   With the increasing popularity of new energy electric vehicles, the demand for lithium-ion batteries (LIBs) has been growing rapidly, which will produce a large number of spent LIBs. Therefore, recycling of spent LIBs has become an urgent task to be solved, otherwise it will inevitably lead to serious environ-mental pollution. Herein, a unique recycling strategy is proposed to achieve the concurrent reuse of cath-ode and anode in the spent graphite/LiFePO4 batteries. Along with such recycling process, a unique cathode composed of recycled LFP/graphite (RLFPG) with cation/anion-co-storage ability is designed for new-type dual-ion battery (DIB). As a result, the recycle-derived DIB of Li/RLFPG is established with good electrochemical performance, such as an initial discharge capacity of 117.4 mA h g-1 at 25 mA g-1 and 78% capacity retention after 1000 cycles at 100 mA g-1. The working mechanism of Li/RLFPG DIB is also revealed via in situ X-ray diffraction and electrode kinetics studies. This work not only presents a far-reaching significance for large-scale recycling of spent LIBs in the future, but also proposed a sustainable and economical method to design new-type secondary batteries as recycling of spent LIBs.

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Polar interaction of polymer host-solvent enables stable solid electrolyte interphase in composite lithium metal anodes Peng Shi, Ze-Yu Liu, Xue-Qiang Zhang, Xiang Chen, Nan Yao, Jin Xie, Cheng-Bin Jin, Ying-Xin Zhan, Gang Ye, Jia-Qi Huang, Stephens Ifan E L, Titirici Maria-Magdalena, Qiang Zhang 2022, 64(1): 172-178.  DOI: 10.1016/j.jechem.2021.04.045 Abstract ( 17 )   PDF (3273KB) ( 7 )   The lithium (Li) metal anode is an integral component in an emerging high-energy-density rechargeable battery. A composite Li anode with a three-dimensional (3D) host exhibits unique advantages in sup-pressing Li dendrites and maintaining dimensional stability. However, the fundamental understanding and regulation of solid electrolyte interphase (SEI) , which directly dictates the behavior of Li plating/ stripping, are rarely researched in composite Li metal anodes. Herein, the interaction between a polar polymer host and solvent molecules was proposed as an emerging but effective strategy to enable a stable SEI and a uniform Li deposition in a working battery. Fluoroethylene carbonate molecules in elec-trolytes are enriched in the vicinity of a polar polyacrylonitrile (PAN) host due to a strong dipole-dipole interaction, resulting in a LiF-rich SEI on Li metal to improve the uniformity of Li deposition. A composite Li anode with a PAN host delivers 145 cycles compared with 90 cycles when a non-polar host is employed. Moreover, 60 cycles are demonstrated in a 1.0 Ah pouch cell without external pressure. This work provides a fresh guidance for designing practical composite Li anodes by unraveling the vital role of the synergy between a 3D host and solvent molecules for regulating a robust SEI.

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A guide to use fluorinated aromatic bulky cations for stable and high-performance 2D/3D perovskite solar cells: The more fluorination the better? Lei Wang, Qin Zhou, Zilong Zhang, Wenbo Li, Xiaobing Wang, Qing Tian, Xiaoyan Yu, Ting Sun, Jihuai Wu, Bao Zhang, Peng Gao 2022, 64(1): 179-189.  DOI: 10.1016/j.jechem.2021.04.063 Abstract ( 9 )   PDF (8117KB) ( 4 )   While serious stability issues impede the commercialization of perovskite solar cells (PSCs) , two-dimensional (2D) perovskites based on fluorinated bulky cations have emerged as more intrinsically stable materials. However, the influence of fluorination degree of the bulky aromatic cation on the per-formance of resulting PSCs has not been scrutinized. Here, 2D perovskites (FxPEA) 2PbI4 (x= 1, 2, 3, 5) are grown in situ on the surface of the three-dimensional (3D) perovskite and demonstrate effective passiva-tion of the surface defects of 3D perovskite. The power conversion efficiency (PCE) of the optimized devices were boosted from 20.75% for the control device to 21.09%, 22.06%, 22.74% and 21.86% for 2D/3D devices treated with 4-fluorophenethylamine iodide, 3,5-difluorophenylethylamine iodide, 2,4,5-trifluoroethylphenylethylamine iodide, and 1,2,3,4,5-pentafluorophenylethylamine iodide, respec-tively. We firstly reported two unexplored RP-type layered perovskites with F2PEAI and F3PEAI as bulky cations. The combined experimental and theoretical analysis revealed the reasons behind the various morphology, device performances, dynamic behavior, and humidity stability. The best performing F5PEAI-treated device retaining 95.0% of its initial PCE under ambient atmosphere (with RH of 60% ± 5%) without encapsulation for 300 h storage. This work provides useful guidance for selecting flu-orinated bulky cations with different molecular electronic properties, which will play an essential role in further improving the performance/stability of PSCs for the sake of further commercialization.

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Effect of temperature on formation and evolution of solid electrolyte interphase on Si@Graphite@C anodes Hong Dong, Jie Wang, Peng Wang, Hao Ding, Ru Song, Ning-Shuang Zhang, Dong-Ni Zhao, Li-Juan Zhang, Shi-You Li 2022, 64(1): 190-200.  DOI: 10.1016/j.jechem.2021.04.055 Abstract ( 5 )   PDF (7266KB) ( 3 )   Studies on the formation and evolution of the solid electrolyte interface (SEI) film under different ambient temperatures are important to understand the failure behavior of lithium-ion batteries (LIBs). Herein, in-situ electrochemical impedance spectroscopy (EIS) test is performed on the whole discharge process of Si@Graphite@C/Li cell at 0, 25 and 55 ℃, respectively. Combining with scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy characterizations,it is found that the SEI film undergoes a complicated evolution process of pre-formation, self-improvement and gradual decay in succession at 25 ℃. Besides, due to the dissolution of organo-alkyl lithium at high temperature, the formed film is mainly composed of LiF, Li2CO3 and other inorganic salts, which helps to decrease the impedance. However, the electrolyte is consumed continuously on the new exposed interface, leading to the degraded performance of the cell. Moreover, the dynamic properties of Li+ ions are poor at low temperature, though the migration ability of Li+ ions in the solid phase can be improved as the cycle goes on. Therefore, the development and application of in-situ EIS technology are expected to become an important means to explain the electrochemical performance of batteries.

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Carbon quantum dots modified TiO2 composites for hydrogen production and selective glucose photoreforming Heng Zhao, Xinti Yu, Chao-Fan Li, Wenbei Yu, Aiguo Wang, Zhi-Yi Hu, Steve Larter, Yu Li, Md Golam Kibria, Jinguang Hu 2022, 64(1): 201-208.  DOI: 10.1016/j.jechem.2021.04.033 Abstract ( 9 )   PDF (6771KB) ( 2 )   Lignocellulosic biomass photoreforming is a promising and alternative strategy for both sustainable H2 production and biomass valorization with infinite solar energy. However, harsh reaction conditions (high alkalinity or toxic organic solvents) , with low biomass conversion and selectivity are often reported in literature. In this work, we report glucose photoreforming for coproduction of H2 and arabinose with improved selectivity under neutral condition using carbon quantum dots (CQDs) modified TiO2 compos-ites. We show that the conventional CQDs fabricated by a facile one-step hydrothermal process could be endowed with novel color changing property, due to the particle aggregation under the regulation of inci-dent light. The as-fabricated CQDs/TiO2 composites with certain colored CQDs could greatly improve glu-cose to arabinose conversion selectivity (~75%) together with efficient hydrogen evolution (up to 2.43 mmolh-1g-1) in water. The arabinose is produced via the direct C1-C2 α-scissions mechanism with reac-tive oxygen species of .O-2 and .OH, as evidenced by 13C labeled glucose and the electron spin-resonance (ESR) studies, respectively. This work not only sheds new lights on CQDs assisted photobiorefinery for biomass valorization and H2 coproduction, but also opens the door for rationale design of different col-ored CQDs and their potential applications for solar energy utilization in the noble-metal-free system.

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Lead-free molecular one-dimensional perovskite for efficient X-ray detection Haojin Li, Xin Song, Chuang Ma, Zhuo Xu, Nuo Bu, Tinghuan Yang, Qingyue Cui, Lili Gao, Zhou Yang, Fei Gao, Guangtao Zhao, Zhaolai Chen, Zicheng Ding, Kui Zhao, ShengzhongLiu 2022, 64(1): 209-213.  DOI: 10.1016/j.jechem.2021.04.040 Abstract ( 16 )   PDF (4946KB) ( 6 )

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Role of transition metal oxides in g-C3N4-based heterojunctions for photocatalysis and supercapacitors Liqi Bai, Hongwei Huang, Shixin Yu, Deyang Zhang, Haitao Huang, Yihe Zhang 2022, 64(1): 214-235.  DOI: 10.1016/j.jechem.2021.04.057 Abstract ( 14 )   PDF (12966KB) ( 4 )   g-C3N4 emerges as a star 2D photocatalyst due to its unique layered structure, suitable band structure and low cost. However, its photocatalytic application is limited by the fast charge recombination and low photoabsorption. Rationally designing g-C3N4-based heterojunction is promising for improving photocat-alytic activity. Besides, g-C3N4 exhibits great potentials in electrochemical energy storage. In view of the excellent performance of typical transition metal oxides (TMOs) in photocatalysis and energy storage, this review summarized the advances of TMOs/g-C3N4 heterojunctions in the above two areas. Firstly, we introduce several typical TMOs based on their crystal structures and band structures. Then, we sum-marize different kinds of TMOs/g-C3N4 heterojunctions, including type I/II heterojunction, Z-scheme, p-n junction and Schottky junction, with diverse photocatalytic applications (pollutant degradation, water splitting, CO2 reduction and N2 fixation) and supercapacitive energy storage. Finally, some promising strategies for improving the performance of TMOs/g-C3N4 were proposed. Particularly, the exploration of photocatalysis-assisted supercapacitors was discussed.

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High-efficiency single and tandem fullerene solar cells with asymmetric monofluorinated diketopyrrolopyrrole-based polymer Shafket Rasool, Quoc Viet Hoang, Doan Van Vu, Chang Eun Song, Hang Ken Lee, Sang Kyu Lee, Jong-Cheol Lee, Sang-Jin Moon, Won Suk Shin 2022, 64(1): 236-245.  DOI: 10.1016/j.jechem.2021.04.032 Abstract ( 6 )   PDF (4890KB) ( 2 )   Design and synthesis of low bandgap (LBG) polymer donors is inevitably challenging and their process-ability from a non-halogenated solvent system remains a hurdle to overcome in the area of high-performance polymer solar cells (PSCs). Due to a high aggregation tendency of LBG polymers, especially diketopyrrolopyrrole (DPP) -based polymers coupled with bithiophenes in the polymer backbones, their widespread adoption in non-halogenated solvent-processed PSCs has been limited. Herein, a novel LBG DPP-based polymer, called PDPP4T-1F with asymmetric arrangement of fluorine atom, has been success-fully synthesized and showed an outstanding power conversion efficiency (PCE) of 10.10% in a single-junction fullerene-based PSCs. Furthermore, an impressive PCE of 13.21% has been achieved in a tandem device from a fully non-halogenated solvent system, which integrates a wide bandgap PDTBTBz-2F poly-mer in the bottom cell and LBG PDPP4T-1F polymer in the top cell. The achieved efficiency is the highest value reported in the literature to date in fullerene-based tandem PSCs. We found that a uniformly dis-tributed interpenetrating fibril network with nano-scale phase separation and anisotropy of the polymer backbone orientation for efficient charge transfer/transport and suppressed charge recombination in PDPP4T-1F-based PSCs led to outstanding PCEs in single and tandem-junction PSCs.

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Interfacial parasitic reactions of zinc anodes in zinc ion batteries: Underestimated corrosion and hydrogen evolution reactions and their suppression strategies Aruuhan Bayaguud, Yanpeng Fu, Changbao Zhu 2022, 64(1): 246-262.  DOI: 10.1016/j.jechem.2021.04.016 Abstract ( 17 )   PDF (12901KB) ( 14 )   Featured with high power density, improved safety and low-cost, rechargeable aqueous zinc-ion batter-ies (ZIBs) have been revived as possible candidates for sustainable energy storage systems in recent years. However, the challenges inherent in zinc (Zn) anode, namely dendrite formation and interfacial parasitic reactions, have greatly impeded their practical application. Whereas the critical issue of dendrite forma-tion has attracted widespread concern, the parasitic reactions of Zn anodes with mildly acidic electrolytes have received very little attentions. Considering that the low Zn reversibility that stems from interfacial parasitic reactions is the major obstacle to the commercialization of ZIBs, thorough understanding of these side reactions and the development of correlative inhibition strategies are significant. Therefore, in this review, the brief fundamentals of corrosion and hydrogen evolution reactions at Zn surface is pre-sented. In addition, recent advances and research efforts addressing detrimental side reactions are reviewed from the perspective of electrode design, electrode-electrolyte interfacial engineering and elec-trolyte modification. To facilitate the future researches on this aspect, perspectives and suggestions for relevant investigations are provided lastly.

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A perspective on the electrocatalytic conversion of carbon dioxide to methanol with metallomacrocyclic catalysts Xinyan Liu, Bo-Quan Li, Bing Ni, Lei Wang, Hong-Jie Peng 2022, 64(1): 263-275.  DOI: 10.1016/j.jechem.2021.04.059 Abstract ( 12 )   PDF (4269KB) ( 4 )   Electrocatalytic carbon dioxide reduction (CO2R) presents a promising route to establish zero-emission carbon cycle and store intermittent renewable energy into chemical fuels for steady energy supply. Methanol is an ideal energy carrier as alternative fuels and one of the most important commodity chem-icals. Nevertheless, methanol is currently mainly produced from fossil-based syngas, the production of which yields tremendous carbon emission globally. Direct CO2R towards methanol poses great potential to shift the paradigm of methanol production. In this perspective, we focus our discussions on producing methanol from electrochemical CO2R, using metallomacrocyclic molecules as the model catalysts. We discuss the motivation of having methanol as the sole CO2R product, the documented application of met-allomacrocyclic catalysts for CO2R, and recent advance in catalyzing CO2 to methanol with cobalt phthalocyanine-based catalysts. We attempt to understand the key factors in determining the activity, selectivity, and stability of electrocatalytic CO2-to-methanol conversion, and to draw mechanistic insights from existing observations. Finally, we identify the challenges hindering methanol electrosyn-thesis directly from CO2 and some intriguing directions worthy of further investigation and exploration.

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Steam activation of Fe-N-C catalyst for advanced power performance of alkaline hydrazine fuel cells Sooan Bae, Jihyeon Park, Yuna Hwang, Jin-Soo Park, Jaeyoung Lee, Beomgyun Jeong 2022, 64(1): 276-285.  DOI: 10.1016/j.jechem.2021.04.029 Abstract ( 10 )   PDF (5381KB) ( 6 )   Alkaline hydrazine liquid fuel cells (AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts. Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction (ORR) , the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites. With this thick catalyst layer, it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer. Herein, we prepare a Fe-N-C catalyst with magnetite parti-cles and hierarchical pore structure by steam activation. The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses. Based on a systematic characterization, we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs, and magnetite nanoparticles act as surface modifiers to reduce the interfacial resistance between the electrode and the ion-exchange membrane.

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Biomass seaweed-derived nitrogen self-doped porous carbon anodes for sodium-ion batteries: Insights into the structure and electrochemical activity Chenrayan Senthil, Jae Woo Park, Nitheesha Shaji, Gyu Sang Sim, Chang Woo Lee 2022, 64(1): 286-295.  DOI: 10.1016/j.jechem.2021.04.060 Abstract ( 20 )   PDF (6117KB) ( 5 )   Sustainable transformation and efficient utilization of biomasses and their derived materials are environ-mentally as well as economically compliant strategies. Biomass seaweed-derived nitrogen self-doped porous carbon with tailored surface area and pore structures are prepared through carbonization and activation. The influence of carbonization temperature on morphology, surface area, and heteroatom dopants are investigated to optimize sodium-ion storage capability. Seaweed-derived nitrogen self-doped activated carbon (SAC) as anode materials for sodium-ion batteries exhibits remarkable reversible capacity of 303/192 mAh g-1 after 100/500 cycles at current densities of 100/200 mA g-1, respectively, and a good rate capability. The interconnected and porous conducting nature along with the heteroatom dopant role in creating defective sites and charge stabilization are favorable for ion storage and diffusion and electron transport, indicating the electrodes can offer improved electrochemical performances. In addition, post-mortem analysis of the cycled carbon electrodes through ex-situ tools demonstrates the sodium-ion storage mechanism.

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Fe-N-C catalysts for oxygen electroreduction under external magnetic fields: Reduction of magnetic O2 to nonmagnetic H2O Wojciech Kiciński, Jakub P.Sęk, Agata Kowalczyk, Sylwia Turczyniak-Surdacka, Anna M.Nowicka, Sławomir Dyjak, Bogusław Budner, Mikołaj Donten 2022, 64(1): 296-308.  DOI: 10.1016/j.jechem.2021.04.048 Abstract ( 15 )   PDF (3237KB) ( 6 )   An extensive analysis of iron-nitrogen-carbon (Fe-N-C) electrocatalysts synthesis and activity is presented concerning synthesis conditions such as initial Fe content, pyrolysis temperature and atmosphere (inert N2, reducing NH3, oxidizing Cl2 and their sequential combinations) and the influence of an external magnetic field on their performance in oxygen reduction reaction (ORR). Thermosetting porous polymers doped with FeCl3 were utilized as the Fe-N-C catalysts precursors. The pyrolysis temperature was varied within a 700-900 °C range. The temperature and atmosphere of pyrolysis strongly affect the porosity and composition of the resultant Fe-N-C catalysts, while the initial amount of Fe precursor shows much weaker impact. Pyrolysis under NH3 yields materials similar to those pyrolyzed under an inert atmosphere (N2). In contrast, pyrolysis under Cl2 yields carbon of peculiar character with highly disordered structure and extensive microporosity. The application of a static external magnetic field strongly enhances the ORR process (herein studied in an alkaline environment) and the enhancement correlates with the Fe content in the Fe-N-C catalysts. The Fe-N-C materials containing ferromagnetic iron phase embedded in N-doped microporous carbon constitute attractive catalysts for magnetic field-aided anion exchange membrane fuel cell technology.

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Stable Li storage in micron-sized SiOx particles with rigid-flexible coating Ming-Yan Yan, Zhu Liu, Zhuo-Ya Lu, Lin-Bo Huang, Ke-Cheng Jiang, Hong-Liang Li, Sen Xin, Quan Xu, Yu-Guo Guo 2022, 64(1): 309-314.  DOI: 10.1016/j.jechem.2021.04.066 Abstract ( 8 )   PDF (6185KB) ( 4 )   Micrometre-sized electrode materials have distinct advantages for battery applications in terms of energy density, processability, safety and cost. For the silicon monoxide anode that undergoes electro-chemical alloying reaction with Li, the Li (de) intercalation by micron-sized active particles usually accompanies with a large volume variation, which pulverizes the particle structure and leads to rapidly faded storage performance. In this work, we proposed to stabilize the electrochemistry vs. Li of the micron-SiOx anode by forming a rigid-flexible bi-layer coating on the particle surface. The coating con-sists of pyrolysis carbon as the inner layer and polydopamine as the outer layer. While the inner layer guarantees high structural rigidity at particle surface and provides efficient pathway for electron conduc-tion, the outer layer shows high flexibility for maintaining the integrity of micrometre-sized particles against drastic volume variation, and together they facilitate formation of stable solid electrolyte inter-face on the SiOx particles. A composite anode prepared by mixing the coated micron-SiOx with graphite delivered improved Li storage performance, and promised a high-capacity, long-life LiFePO4/SiOx-graphite pouch cell. Our strategy provides a general and feasible solution for building high-energy rechargeable batteries from micrometre-sized electrode materials with significant volume variation.

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Ultrasmall Pt2Sr alloy nanoparticles as efficient bifunctional electrocatalysts for oxygen reduction and hydrogen evolution in acidic media Xiangnan Liu, Shaoyun Hao, Guokui Zheng, Zhiwei Su, Yahui Wang, Qiqi Wang, Lecheng Lei, Yi He, Xingwang Zhang 2022, 64(1): 315-322.  DOI: 10.1016/j.jechem.2021.04.065 Abstract ( 7 )   PDF (7109KB) ( 2 )   Electrocatalytic oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER) in acidic media are vital for the applications of renewable energy electrolyzers. However, the low mass activity of noble Pt urgently needs to be improved due to the strong binding energetics of oxygen species (*O) with Pt sites. Here we report fine PtxSr alloy (~2 nm) supported on N-doped carbon (NC) pyrolyzing from ZIF-8 as bifunctional electrocatalysts toward ORR and HER in acidic media. The representative Pt2Sr/NC exhi-bits an onset potential of 0.94 V vs. RHE and half-wave potential of 0.84 V toward ORR, and a low over-potential of 27 mV (10 mA cm-2) toward HER, respectively. Significantly, the mass activities of Pt2Sr/NC are 6.2 and 2.6 times higher than that of Pt/C toward ORR (at 0.9 V) and HER (at -30 mV) , respectively. Simultaneously, Pt2Sr/NC possesses a retention rate of 90.97% toward acidic ORR after 35000 s of contin-uous operation. Through density functional theory (DFT) calculations and X-ray photoelectron spec-troscopy analysis, the incorporation of Sr into Pt forming Pt2Sr alloy redistributes the electronic structures of Pt-Pt bonds, changing the rate-determining step for the ORR on Pt sites from the formation of *OH from *O to the generation of *OOH along with decreasing the energy barrier, which is also con-firmed by the downshift of d band center. Meanwhile, the downshift of d band center also leads to the optimization of the adsorption energy (H*) with Pt, significantly improving Pt2Sr/NC toward HER.

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High-performance polymer electrolyte membranes incorporated with 2D silica nanosheets in high-temperature proton exchange membrane fuel cells Zunmin Guo, Jianuo Chen, Jae Jong Byun, Rongsheng Cai, Maria Perez-Page, Madhumita Sahoo, Zhaoqi Ji, Sarah J. Haigh, Stuart M. Holmes 2022, 64(1): 323-334.  DOI: 10.1016/j.jechem.2021.04.061 Abstract ( 9 )   PDF (6064KB) ( 3 )   Silica nanosheets (SN) derived from natural vermiculite (Verm) were successfully incorporated into polyethersulfone-polyvinylpyrrolidone (PES-PVP) polymer to fabricate high-temperature proton exchange membranes (HT-PEMs). The content of SN filler was varied (0.1-0.75 wt%) to study its influ-ence on proton conductivity, power density and durability. Benefiting from the hydroxyl groups of SN that enable the formation of additional proton-transferring pathways, the inorganic-organic membrane displayed enhanced proton conductivity of 48.2 mS/cm and power density of 495 mW/cm2 at 150 °C without humidification when the content of SN is 0.25 wt%. Furthermore, exfoliated SN (E-SN) and sul-fonated SN (S-SN) , which were fabricated by a liquid-phase exfoliation method and silane condensation, respectively, were embedded in PES-PVP polymer matrix by a simple blending method. Due to the sig-nificant contribution from sulfonic groups in S-SN, the membrane with 0.25 wt% S-SN reached the high-est proton conductivity of 51.5 mS/cm and peak power density of 546 mW/cm2 at 150 °C, 48% higher than the pristine PES-PVP membranes. Compared to unaltered PES-PVP membrane, SN added hybrid compos-ite membrane demonstrated excellent durability for the fuel cell at 150 °C. Using a facile method to pre-pare 2D SN from natural clay minerals, the strategy of exfoliation and functionalization of SN can be potentially used in the production of HT-PEMs.

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Insight of K-deficient layered KxMnO2 cathode for potassium-ions batteries Tiezhong Liu, Shuang Hou, Youpeng Li, Shoufeng Xue, Junhua Hu, Haikuo Fu, Chenghao Yang, Lingzhi Zhao 2022, 64(1): 335-343.  DOI: 10.1016/j.jechem.2021.04.062 Abstract ( 11 )   PDF (15349KB) ( 1 )   Potassium-ions batteries (PIBs) are attracting increasing attention as up-and-coming youngster in large-scale grid-level energy storage benefiting from its low-cost and high energy density. Nevertheless, enough researches regarding indispensable cathode materials for PIBs are badly absent. Herein, we syn-thesize K-deficient layered manganese-based oxides (P2-K0.21MnO2 and P3-K0.23MnO2) and investigate them as cathode of PIBs for the first time. As the newcomer of potassium-containing layered manganese-based oxides (KxMnO2) group, P2-K0.21MnO2 delivers high discharge capacity of 99.3 mAh g-1 and P3-K0.23MnO2 exhibits remarkable capacity retention rate of 75.5%. Besides, in-situ XRD and ex-situ XRD measurements reveal the reversible phase transition of P2-K MnO and P3-K MnO with the potassium-ions extraction and reinsertion, respectively. This work contributes to a better under-standing for the potassium storage in K-deficient layered KxMnO2 (x ≤ 0.23) , possessing an important basic scientific significance for the exploitation and application of layered KxMnO2 in PIBs.

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Is it universal that the layered-spinel structure can improve electrochemical performance? Daqiang Wang, Zhenguo Wu, Wei Xiang, Yuxia Liu, Gongke Wang, Kanghui Hu, Qi Xu, Yang Song, Xiaodong Guo 2022, 64(1): 344-353.  DOI: 10.1016/j.jechem.2021.04.030 Abstract ( 8 )   PDF (21210KB) ( 8 )   The introduction of spinel phase to form the layered-spinel structure (LSS) is an effective way to improve the electrochemical performance of Li-and Mn-rich layered oxides (LMR). But is this structure universal for all LMR systems? In this work, different Mn/Ni ratio systems with the LSS are discussed in detail. It is found that, high discharge capacity (200.8 mA h g-1 at 1C rate; 1C = 250 mA h g-1) as well as high capacity-retention (94% at 1C rate after 100 cycles) can be achieved by forming the LSS for low-Ni system (Mn/Ni = 5.0). However, the capacity retention decreases severely in the high-Ni system (Mn/Ni = 3.5, 2.6). For example, when the ratio of Mn/Ni is 3.5, the capacity-retention of the layered-spinel sample was only 65.8%, compared to the 83% of the original LMR sample. The Ex-situ XRD, XPS, and HRTEM results demonstrate that the introduction of spinel phase in high-Ni system accelerates the transition and collapse of the crystal structure. This work provides guidance for optimizing the proportions of ele-ments and the design of structures for the LMR.

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Layered Ag-graphene films synthesized by Gamma ray irradiation for stable lithium metal anodes in carbonate-based electrolytes Jiaxiang Liu, Haoshen Ma, Zhipeng Wen, Huiyang Li, Jin Yang, Nanbiao Pei, Peng Zhang, Jinbao Zhao 2022, 64(1): 354-363.  DOI: 10.1016/j.jechem.2021.04.044 Abstract ( 7 )   PDF (9690KB) ( 2 )   Lithium metal batteries are considered as high energy density battery systems with very promising pro-spects and have been widely studied. However, The uncontrollable plating/stripping behavior, infinite volume change and dendrites formation of lithium metal anode restrict the application. The uncontrolled nucleation of lithium caused by the nonuniform multi-physical field distributions, can lead to the unde-sirable lithium deposition. Herein, a graphene composite uniformly loaded with Ag nano-particles (Ag NPs) is prepared through a facile Gamma ray irradiation method and assembled into self-supported film with layered structure (Ag-rGO film). When such film is used as a lithium metal anode host, the uncon-trolled deposition is converted into a highly nucleation-induced process. On one hand, the Ag NPs dis-tributed between the interlayers of graphene can preferentially induce lithium nucleation and enable uniform deposition morphology of lithium between interlayers. On the other hand, the stable layered graphene structure can accommodate volume change, stabilize the interface between anode and elec-trolyte and inhibit dendrites formation. Therefore, the layered Ag-rGO film as anode host can reach a high Coulombic efficiency over 93.3% for 200 cycle (786 h) at a current density of 1 mA cm-2 for 2 mAh cm-2 in carbonate-based electrolyte. This work proposes a facile Gamma ray irradiation method to prepare metal/3D-skeleton structure as lithium anode host and demonstrates the potential to regulate the lithium metal deposition behaviors via manipulating the distribution of lithiophilic metal (e.g. Ag) in 3D frameworks. This may offer a practicable thinking for the subsequent design of the lithium metal anode.

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Boosting overall water splitting by incorporating sulfur into NiFe(oxy) hydroxide Chiho Kim, Seong Hyun Kim, Seunghun Lee, Ilyeong Kwon, Seong Hyun Kim, Shinho Kim, Changgyu Seok, Yoo Sei Park, Yangdo Kim 2022, 64(1): 364-371.  DOI: 10.1016/j.jechem.2021.04.067 Abstract ( 11 )   PDF (4721KB) ( 4 )   Developing highly active and cost-effective electrocatalysts for enhancing the hydrogen evolution reac-tion (HER) and oxygen evolution reaction (OER) is a significant challenge for overall water splitting. Sulfur-incorporated nickel iron (oxy) hydroxide (S-NiFeOOH) nanosheets were directly grown on com-mercial nickel foam using a galvanic corrosion method and a hydrothermal method. The incorporation of sulfur into NiFeOOH enhanced the catalytic activity for the HER and OER in 1 M KOH electrolyte. The enhanced catalytic activity is attributed to the change in the local structure and chemical states due to the incorporation of sulfur. High performance for overall water splitting was achieved with an alkaline water electrolyzer. This was realized by employing S-NiFeOOH as a bifunctional electrocatalyst, thereby outperforming a water electrolyzer that requires the usage of precious metal electrocatalysts (i.e., Pt/C as the HER electrocatalyst and IrO2 as the OER electrocatalyst). Moreover, when driven by a commercial silicon solar cell, an alkaline water electrolyzer that uses S-NiFeOOH as a bifunctional elec-trocatalyst generated hydrogen under natural illumination. This study shows that S-NiFeOOH is a promising candidate for a large-scale industrial implementation of hydrogen production for overall water splitting because of its low cost, high activity, and durability. In addition, the solar-driven water elec-trolyzer using S-NiFeOOH as a bifunctional electrocatalyst affords the opportunity for developing effec-tive and feasible solar power systems in the future.

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A flame retardant separator modified by MOFs-derived hybrid for safe and efficient Li-S batteries Na Wu, Junling Wang, Can Liao, Longfei Han, Lei Song, Yuan Hu, Xiaowei Mu, Yongchun Kan 2022, 64(1): 372-384.  DOI: 10.1016/j.jechem.2021.05.001 Abstract ( 10 )   PDF (10966KB) ( 1 )   In this work, we have successfully prepared a novel separator modified with N, S co-doped carbon frame-work (named NSPCF) with confined CoS2 nanoparticles and rooted carbon nanotubes material (named NSPCF@CoS2) to apply for high-performance Lithium-Sulfur batteries (Li-S batteries). Robust carbon structure with large specific surface can act as a physical barrier and possess physical adsorption effect on lithium polysulfides (LiPSs). In addition, highly-conductive carbon can improve integral conductivity, leading to the fast charge transport and reaction kinetics. Also, doping heteroatoms could form more active sites to adsorb LiPSs strongly so that modified separator could inhibit the shuttle effect effectively. Moreover, the presence of CoS2 further enhances the ability of modified separator to trap LiPSs owing to the Lewis acid-base action. As a result, the NSPCF@CoS2@C-150 battery can deliver initial discharge capacities of 863.0, 776.2, 649.1 and 489.4 mAh g-1 at 0.1, 0.5, 1 and 2C with a high sulfur loading of 2.04 mg cm-2, respectively. Notably, when turning the current density back to 0.1C, its discharge capacity can recover to 1008.7 mAh g-1. In addition, the modified separators exhibit outstanding capacities to restrain the growth of lithium dendrites. It is noteworthy that the flame retardant performances of Li-S batteries are improved dramatically owing to the novel structures of modified separators. This ration-ally designed separator endows Li-S batteries with higher safety and excellent electrochemical perfor-mances, providing a feasible strategy for practical application of Li-S batteries.

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Novel fusiform core-shell-MOF derived intact metal@carbon composite: An efficient cathode catalyst for aqueous and solid-state Zn-air batteries Di Zhou, Hongquan Fu, Jilan Long, Kui Shen, Xinglong Gou 2022, 64(1): 385-394.  DOI: 10.1016/j.jechem.2021.05.011 Abstract ( 8 )   PDF (13815KB) ( 1 )   Owing to the varied mechanisms of ORR/OER, exploiting cost-effective bifunctional catalysts with robust ORR/OER activities and excellent performances in Zn-air batteries is still a challenge. In this work, the Co/ CoO@NSC bifunctional catalyst is obtained by using Zn-MOF@Co-MOF as self-template. The Co/CoO@NSC composite has interconnected porous architecture with intact metal@carbon structure, exhibiting supe-rior electrocatalytic activities toward ORR and OER that can be comparable with the Pt/C and RuO2 cat-alysts, respectively. The Co/CoO@NSC-based aqueous Zn-air battery achieves a high specific capacity (759.7 mAh/g) and energy density (990.5 Wh/kg) , and ultra-long rechargeable property (more than 400 h/1200 cycles). The Co/CoO@NSC-based solid-state Zn-air battery also delivers an excellent perfor-mance with a long cycle life (more than 143 h/858 cycles). Most importantly, the newly synthesized and recharged Co/CoO@NSC-based solid-state Zn-air battery can be used to light up a 2 V LED lamp for more than 28 h, demonstrating the superior practicability as rechargeable power source.

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Promote the conductivity of solid polymer electrolyte at room temperature by constructing a dual range ionic conduction path Ruiyang Li, Haiming Hua, Yuejing Zeng, Jin Yang, Zhiqiang Chen, Peng Zhang, Jinbao Zhao 2022, 64(1): 395-403.  DOI: 10.1016/j.jechem.2021.04.037 Abstract ( 6 )   PDF (5012KB) ( 2 )   Poly (ethylene oxide) (PEO) is a classic matrix model for solid polymer electrolyte which can not only dis-sociate lithium-ions (Li+) , but also can conduct Li+ through segmental motion in long-range. However, the crystal aggregation state of PEO restricts the conduction of Li+ especially at room temperature. In this work, an amorphous polymer electrolyte with ethylene oxide (EO) and propylene oxide (PO) block struc-ture (B-PEG@DMC) synthesized by the transesterification is firstly obtained, showing an ionic conductiv-ity value of 1.1 10-5 S/cm at room temperature (25 °C). According to the molecular dynamics (MD) simulation, the PO segments would lead to an inconsecutive and hampered conduction of Li+, which is not beneficial to the short range conduction of Li+. Thus the effect of transformation of aggregation state on the improvement of ionic conductivity is not enough, it is necessary to further consider the different coupled behaviours of EO and PO segments with Li+. In this way, we blend this amorphous polymer (B-PEG@DMC) with PEO to obtain a dual range ionic conductive solid polymer electrolyte (D-SPE) with fur-ther improved ionic conductivity promoted by constructing a dual range fast ionic conduction, which eventually shows a further improved ionic conductivity value of 2.3 × 10-5 S/cm at room temperature.

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Electrochemical conversion of carbon dioxide in molten salts: In-situand beyond Shuangxi Jing, Mingyong Wang, Wei Xiao 2022, 64(1): 404-405.  DOI: 10.1016/j.jechem.2021.05.012 Abstract ( 5 )   PDF (1368KB) ( 3 )

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Layered double hydroxide (LDH)-based materials: A mini-review on strategies to improve the performance for photocatalytic water splitting Hanane Boumeriame, Eliana S. Da Silva, Alexey S. Cherevan, Tarik Chafik, Joaquim L. Faria, Dominik Eder 2022, 64(1): 406-431.  DOI: 10.1016/j.jechem.2021.04.050 Abstract ( 22 )   PDF (12733KB) ( 7 )   The high energy demand we currently face in society and the subsequent large consumption of fossil fuels cause its depletion and increase the pollution levels. The quest for the production of clean energy from renewable and sustainable sources remains open. The conversion of solar energy into hydrogen via the water-splitting process, assisted by photoresponsive semiconductor catalysts, is one of the most promising technologies. Significant progress has been made on water splitting in the past few years and a variety of photocatalysts active not only under ultra-violet (UV) light but especially with the visible part of the electromagnetic spectrum have been developed. Layered double hydroxides (LDH) -based materials have emerged as a promising class of nanomaterials for solar energy applications owing to their unique layered structure, compositional flexibility, tunable bandgaps, ease of synthesis and low manufacturing costs. This review covers the most recent research dedicated to LDH materials for photocatalytic water-splitting applications and encompasses a range of synthetic strategies and post-modifications used to enhance their performance. Moreover, we provide a thorough discussion of the experimental condi-tions crucial to obtaining improved photoactivity and highlight the impact of some specific parameters, namely, catalysts loading, cocatalysts, sacrificial agents, and irradiation sources. This review provides the necessary tools to select the election technique for adequately enhancing the photoactivity of LDH and modified LDH-based materials and concludes with a critical summary that outlines further research directions.

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Self-transforming stainless-steel into the next generation anode material for lithium ion batteries Nimrod Harpak, Guy Davidi, Fernando Patolsky 2022, 64(1): 432-441.  DOI: 10.1016/j.jechem.2021.05.008 Abstract ( 10 )   PDF (4126KB) ( 2 )   Here, an extremely cost-effective and simple method is proposed in order to morphologically self-transform stainless steel from a completely inactive material to a fully operational, nanowire-structured, 3D anode material for lithium ion batteries. The reagentless process of a single heating step of the plain stainless steel in a partially reducing atmosphere, converts the stainless steel into an active anode via metal-selective oxidation, creating vast spinel-structured nanowires directly from the electro-chemically inactive surface. The simple process allows the complete utilization of the 3D mesh structure as the electrochemically-active spinel nanowires greatly enhance the active surface area. The novel mate-rial and architecture exhibits high capacities (~1000 mAh/g after ~400 cycles) , long cycle life (>1100 cycles) and fast rate performance (>2C). Simple modulation of the substrate can result in very high areal and volumetric capacities. Thus, areal capacities greater than 10 mAh/cm2 and volumetric capacities greater than 1400 mAh/cm3 can be achieved. Using the proposed method, the potential reduction in cost from the use of battery-grade graphite is at least an order of magnitude, with considerable better results achieved in terms of capacity and intrinsic structural benefits of the substrate, which include direct con-tact of the active material with the current collector, lack of delamination and binder-free performance. This work provides a new paradigm and a key step in the long route to replace the commercial graphite anode as the next-generation anode material.

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A safe, low-cost and high-efficiency presodiation strategy for pouch-type sodium-ion capacitors with high energy density Congkai Sun, Xiong Zhang, Chen Li, Kai Wang, Xianzhong Sun, Fangyan Liu, Zhong-Shuai Wu, Yanwei Ma 2022, 64(1): 442-450.  DOI: 10.1016/j.jechem.2021.05.010 Abstract ( 11 )   PDF (7451KB) ( 6 )   Sodium-ion capacitors (SICs) have attracted appreciable attention in virtue of the higher energy and power densities compared with their rivals, supercapacitors and sodium-ion batteries. Due to the lack of sodium resources in cathode, presodiation is critical for SICs to further augment performances. However, current presodiation strategy utilizes metallic sodium as the presodiation material. In this strategy, assembling/disassembling of half-cells is required, which is dangerous and increases the time and cost of SIC leading to the restriction of their industrialization and commercialization. Herein we pre-sent a safe, low-cost and high-efficiency presodiation strategy by first employing Na2C2O4 as the sacrifi-cial salt applied in SICs. Na2C2O4 is environmentally friendly and possesses considerably low expenditure. No additional residues remain after sodium extraction ascribed to its ‘‘zero dead mass” property. When paired with commercial activated carbon as the cathode and commercial hard carbon as the anode, the constructed pouch-type SICs exhibit high energy and power densities of 91.7 Wh/kg and 13.1 kW/kg, respectively. This work shows a prospect of realizing the safe and low-cost manufacturing for high-performance SICs commercially.

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Anion effect on Li/Na/K hybrid electrolytes for Graphite//NCA (LiNi0.8Co0.15Al0.05O2) Li-ion batteries Aiman Jrondi, Georgios Nikiforidis, Mérièm Anouti 2022, 64(1): 451-462.  DOI: 10.1016/j.jechem.2021.05.004 Abstract ( 8 )   PDF (9354KB) ( 3 )   The electrolyte is an essential component of a battery system since it is responsible for the conduction of ions between the electrodes. In the quest for cheaper alternatives to common organic electrolytes for lithium-ion batteries (LIB) , we formulated hybrid electrolytes comprising a mixture of Na, K, and Li alka-line salts with ethylene carbonate (EC) , ethyl methyl carbonate (EMC) , and lithium hexafluorophosphate (LiPF6) , giving a total salt concentration of 1.5 M; we determined their physicochemical properties and investigated their electrochemical behavior on a nickel cobalt aluminum oxide (NCA) cathode and gra-phite (Gr) anode. The electrolytes demonstrated a melting transition peak (Tm) , eutectic behavior, and ionic conductivities (~13 mS cm-1) close to those of a commercial LIB electrolyte (SE, EC/EMC + 1 M LiPF6) and activation energies of ca. 3 kJ mol-1. The half-cell coin cells revealed high coulombic efficiency (99%) , specific capacity (175 mAh g-1 at C/10) , and capacity retention (92% for NaCF3SO3) for the NCA cathode and a moderate performance (coulombic efficiency of 98% for 20 cycles) on the graphite anode after the formation of the SEI layer. The hybrid electrolytes were cycled at 25 °C in a Gr//NCA cell yielding specific capacities of ca. 225 mAh g-1 at a C/5 rate, corroborating that the anion plays a key role and high-lighting their potential for energy storage applications.

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Tin phosphide-carbon composite as a high-performance anode active material for sodium-ion batteries with high energy density Zhiqiang Hao, Nikolay Dimov, Jeng-Kuei Chang, Shigeto Okada 2022, 64(1): 463-474.  DOI: 10.1016/j.jechem.2021.04.043 Abstract ( 11 )   PDF (11743KB) ( 4 )   Tin phosphide (Sn4P3) is a promising anode material for sodium-ion batteries because of its relatively large theoretical capacity, appropriate Na+ alloying potential, and good cyclic stability. Herein, the Sn4P3 embedded into a carbon matrix with good rate performance and long cycle life is reported. The Sn4P3-C composite exhibits excellent rate performance (540 mAh g-1 at 5 A g-1) and the highest rever-sible capacity (844 mAh g-1 at 0.5 A g-1) among Sn4P3-based anodes reported so far. Its reversible capac-ity is as high as 705 mAh g-1 even after 100 cycles at 0.5 A g-1. Besides, its initial Coulomb efficiency can reach 85.6%, with the average Coulomb efficiency exceeding 99.75% from the 3rd to 100th cycles. Na2C6O6 is firstly used as a cathode when Sn4P3 acts as anode, and the Na-Sn4P3-C//Na2C6O6 full cell shows excel-lent electrochemical performance. These results demonstrate that the Sn4P3-C composite prepared in this work displays high-rate capability and superior cyclic performance, and thus is a potential anode for sodium ion batteries.

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Synthesis of high-performance nickel hydroxide nanosheets/gadolinium doped-α-MnO2 composite nanorods as cathode and Fe3O4/GO nanospheres as anode for an all-solid-state asymmetric supercapacitor Milan Babu Poudel, Han Joo Kim 2022, 64(1): 475-484.  DOI: 10.1016/j.jechem.2021.05.002 Abstract ( 8 )   PDF (6496KB) ( 2 )   The wide use of manganese dioxide (MnO2) as an electrode in all-solid-state asymmetric supercapacitors (ASCs) remains challenging because of its low electrical conductivity. This complication can be circum-vented by introducing trivalent gadolinium (Gd) ions into the MnO2. Herein, we describe the successful hydrothermal synthesis of crystalline Gd-doped MnO2 nanorods with Ni (OH) 2 nanosheets as cathode, which we combined with Fe3O4/GO nanospheres as anode for all-solid-state ASCs. Electrochemical tests demonstrate that Gd doping significantly affected the electrochemical activities of the MnO2, which was further enhanced by introducing Ni (OH) 2. The GdMnO2/Ni (OH) 2 electrode offers sufficient surface elec-trochemical activity and exhibits excellent specific capacity of 121.8 mA h g-1 at 1 A g-1, appealing rate performance, and ultralong lifetime stability (99.3% retention after 10,000 discharge tests). Furthermore, the GdMnO2/Ni (OH) 2//PVA/KOH//Fe3O4/GO solid-state ASC device offers an impressive specific energy density (60.25 W h kg-1) at a high power density (2332 W kg-1). This investigation thus shows its large potential in developing novel approaches to energy storage devices.

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A protein-enabled protective film with functions of self-adapting and anion-anchoring for stabilizing lithium-metal batteries Chenxu Wang, Xuewei Fu, Shengnan Lin, Jin Liu, Wei-Hong Zhong 2022, 64(1): 485-495.  DOI: 10.1016/j.jechem.2021.05.014 Abstract ( 6 )   PDF (5686KB) ( 2 )   Practical implementations of rechargeable lithium (Li) metal batteries have long been plagued by multi-ple problems of Li anode, such as Li dendrite growth, large volume change, low Coulombic efficiency. Here, we report a protein-enabled film that can provide effective protection for Li metal. The protective film with an integrated design of high flexibility, strong adhesion and high Li-ion transference number (0.80) is fabricated by incorporating denatured zein (corn protein) with polyethylene oxide (PEO) acting as an agent for sustaining the denatured protein chains against refolding via the intermolecular interac-tions between them. Thus, a conformable zein-enabled protective film (zein@PEO) with simultaneous enhancement in flexibility, modulus and adhesion strength is generated to offer both functions of self-adapting and anion-anchoring abilities. The results show that the zein@PEO film is able to accommodate the volume change, reduce the side reactions, and homogenize the ion deposition. Benefiting from these significant properties/functions, the Li/Cu cell with the zein@PEO film delivers prolonged cycle life for over 500 hours with stable performance. Paired with LiMn2O4 cathode, the capacity, cycle stability and rate performance of the cell are remarkably improved as well, demonstrating the effectiveness in stabi-lizing Li metal batteries.

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Low-temperature Li-S batteries enabled by all amorphous conversion process of organosulfur cathode Zhenkang Wang, Xiaowei Shen, Sijie Li, Yuxuan Wu, Tingzhou Yang, Jie Liu, Tao Qian, Chenglin Yan 2022, 64(1): 496-502.  DOI: 10.1016/j.jechem.2021.05.018 Abstract ( 14 )   PDF (3664KB) ( 4 )   The high degree of crystallinity of discharging intermediates of Li-S batteries (Li2S2/Li2S) causes a severe capacity attenuation at low temperatures. Herein, a sulfur-rich polymer is fabricated, which enables all the discharging intermediates to exist in an amorphous state without long-range order, promoting the substantial conversion of discharging intermediates and enhancing Li-S batteries’ performance at low temperatures greatly. This cathode material exhibits excellent performance both at room and low tem-peratures. Even under an extremely low temperature (-40 ℃) , the discharge capacity can remain 67% of that at room temperature. Besides, in-situ UV/Vis spectroscopy and density functional theory calcula-tions reveal that this organosulfur cathode undergoes a new mechanism during discharge. Li2S6 and Li2S3 are the primary discharging intermediates that are quite different from conventional Li-S batteries. These results provide a new direction for a broader range of applications of Li-S batteries.

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Hierarchical structured CoP nanosheets/carbon nanofibers bifunctional eletrocatalyst for high-efficient overall water splitting Xiao-Qiao Xie, Junpeng Liu, Chaonan Gu, Jingjing Li, Yan Zhao, Chun-Sen Liu 2022, 64(1): 503-510.  DOI: 10.1016/j.jechem.2021.05.020 Abstract ( 9 )   PDF (7129KB) ( 4 )   The design of efficient, stable, and economical electrocatalysts for oxygen and hydrogen evolution reaction (OER and HER) is a major challenge for overall water splitting. Herein, a hierarchical structured CoP/carbon nanofibers (CNFs) composite was successfully synthesized and its potential application as a high-efficiency bifunctional electrocatalyst for overall splitting water was evaluated. The synergetic effect of two-dimensional (2D) CoP nanosheets and one-dimensional (1D) CNFs endowed the CoP/CNFs com-posites with abundant active sites and rapid electron and mass transport pathways, and thereby signif-icantly improved the electrocatalytic performances. The optimized CoP/CNFs delivered a current density of 10 mA cm-2 at low overpotential of 325 mV for OER and 225 mV for HER. In the overall water splitting, CoP/CNFs achieved a low potential of 1.65 V at 10 mA cm-2. The facile strategy provided in the present work can facilitate the design and development of multifunctional non-noble metal catalysts for energy applications.

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Dispersion hydrophobic electrolyte enables lithium-oxygen battery enduring saturated water vapor Yinan Zhang, Fangling Jiang, Hao Jiang, Osamu Yamamoto, Tao Zhang 2022, 64(1): 511-519.  DOI: 10.1016/j.jechem.2021.05.013 Abstract ( 9 )   PDF (4189KB) ( 2 )   Li-O2 batteries gain widespread attention as a candidate for next-generation energy storage devices due to their extraordinary theoretic specific energy. The semi-open structure of Li-O2 batteries causes many parasitic reactions, especially related to water. Water is a double-edged sword, which destroys Li anode and simultaneously triggers a solution-based pathway of the discharge product. In this work, hexam-ethyldisilazane (HMDS) is introduced into the electrolyte of an aprotic Li-O2 battery. HMDS has a strong ability to combine with a trace of water to generate a hydrophobic hexamethyldisiloxane (MM) , which eliminates water from the electrolyte decomposition and then prevents the Li anode from producing the insulating LiOH with water. In this case, the hydrophobic MM disperses in the ether-based electrolyte, forming a dispersion hydrophobic electrolyte. This electrolyte can anchor water from the environment on the cathode side, which triggers a solution-based pathway and regulates the growth morphology of the discharge product and consequently increases the discharge capacity. Compared with the Li-O2 battery without the HMDS, the HMDS-containing Li-O2 battery contributes an about 13-fold increase of cyclabil-ity (400 cycles, 1800 h) in the extreme environment of saturated water vapor. This work opens a new approach for directly operating aprotic Li-O2 batteries in ambient air.

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Monitoring dynamics of defects and single Fe atoms in N-functionalized few-layer graphene by in situ temperature programmed scanning transmission electron microscopy Rosa Arrigo, Takeo Sasaki, June Callison, Diego Gianolio, Manfred Erwin Schuster 2022, 64(1): 520-530.  DOI: 10.1016/j.jechem.2021.05.005 Abstract ( 6 )   PDF (5988KB) ( 2 )   In this study, we aim to contribute an understanding of the pathway of formation of Fe species during top-down synthesis of dispersed Fe on N-functionalized few layer graphene, widely used in electrocatal-ysis. We use X-ray absorption spectroscopy to determine the electronic structure and coordination geom-etry of the Fe species and in situ high angle annular dark field scanning transmission electron microscopy combined with atomic resolved electron energy loss spectroscopy to localize these, identify their chem-ical configuration and monitor their dynamics during thermal annealing. We show the high mobility of peripheral Fe atoms, first diffusing rapidly at the trims of the graphene layers and at temperatures as high as 573 K, diffusing from the edge planes towards in-plane locations of the graphene layers forming three-, four-coordinated metal sites and more complexes polynuclear Fe species. This process occurs via bond C-C breaking which partially reduces the extension of the graphene domains. However, the vast majority of Fe is segregated as a metal phase. This dynamic interconversion depends on the structural details of the surrounding graphitic environment in which these are formed as well as the Fe loading. N species appear stabilizing isolated and polynuclear Fe species even at temperatures as high as 873 K. The signif-icance of our results lies on the fact that single Fe atoms in graphene are highly mobile and therefore a structural description of the electroactive sites as such is insufficient and more complex species might be more relevant, especially in the case of multielectron transfer reactions. Here we provide the experimen-tal evidence of the formation of these polynuclear Fe-N sites and their structural characteristics.

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Nitridation-induced metal-organic framework nanosheet for enhanced water oxidation electrocatalysis Na Yao, Hongnan Jia, Zhengyin Fan, Lu Bai, Wei Xie, Hengjiang Cong, Shengli Chen, Wei Luo 2022, 64(1): 531-537.  DOI: 10.1016/j.jechem.2021.05.024 Abstract ( 5 )   PDF (4172KB) ( 2 )   We report the synthesis of nitridation-induced NiFe-MOF through post-synthetic functionalization of ter-minal ligand in NiFe-MOF nanosheet. We directly identify the key factor of amino ligand in N-NiFe-MOF for boosting the OER performance through combining single X-ray crystallographic characterization and in-situ Raman tracking, as well as ex-situ spectroscopy analysis. Density functional theory (DFT) calcula-tions and experimental results indicate irreversible phase reconstruction from amino ligand oxidation prior to OER could lead to the optimized DG*O, resulting in the remarkable OER performance with an overpotential of 258 mV to obtain the current density of 100 mA cm-2 in 1.0 M KOH solution. Our work will provide new strategy for rational designing advanced MOF-based OER electrocatalysts.

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A strategic review on processing routes towards scalable fabrication of perovskite solar cells Yingzhuang Ma, Qing Zhao 2022, 64(1): 538-560.  DOI: 10.1016/j.jechem.2021.05.019 Abstract ( 12 )   PDF (20084KB) ( 4 )   Perovskite solar cells have reached a power-conversion efficiency (PCE) of 25.6%, showing great potential with reliable moisture and heat stability. Most results are achieved on small-area devices, using conven-tional thin-film processing technologies like spin-coating method. However, such approaches may not be upscaled for large-area substrates. Thus, strategies and materials need to be developed for manufacturing processing routes to realize future commercial photovoltaic fabrications. Notable results have been achieved on large-area perovskite solar cells. In this review, similarities and differences of large-area per-ovskite fabrication mechanisms between the various pathways are investigated, especially on the param-eters affecting the nucleation and crystal growth kinetics. Moreover, the methods for large-area transporting layers and electrodes are discussed, and some key issues from cells to modules. Challenges and opportunities are proposed to pave the way of high-efficiency perovskite solar modules.

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Incorporation of γ-aminobutyric acid and cesium cations to formamidinium lead halide perovskites for highly efficient solar cells Yanqiang Hu, Yansu Shan, Zhaolei Yu, Haojie Sui, Ting Qiu, Shufang Zhang, Wei Ruan, Qinfeng Xu, Mengmeng Jiao, Dehua Wang, Yunyi Wu, Chuanlu Yang, Feng Xu 2022, 64(1): 561-567.  DOI: 10.1016/j.jechem.2021.05.025 Abstract ( 6 )   PDF (3371KB) ( 4 )   The stability issue has become one of the main challenges for the commercialization of perovskite solar cells (PSCs). Formamidinium (FA) -based perovskites have shown great promise owing to their improved thermal and moisture stability. However, these perovskites are suffering from phase transition and sep-aration. Here, a method of incorporating of c-aminobutyric acid (GABA) and cesium cations into FAPbI3 is developed to improve the phase stability. It is demonstrated that the crystallinity of a-FAPbI3 phase is greatly improved and the phase transition temperature is significantly dropped. The resultant solar cell therefore obtains a champion power conversion efficiency (PCE) of 23.71%, which is one of the highest efficiencies for methylammonium-free PSCs. Furthermore, it shows an impressively enhanced stability under illumination, exhibiting the great potential of FA-based perovskites for efficient and stable solar cells.

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The formation of crystalline lithium sulfide on electrocatalytic surfaces in lithium-sulfur batteries Yun-Wei Song, Jin-Lei Qin, Chang-Xin Zhao, Meng Zhao, Li-Peng Hou, Yan-Qi Peng, Hong-Jie Peng, Bo-Quan Li 2022, 64(1): 568-573.  DOI: 10.1016/j.jechem.2021.05.023 Abstract ( 8 )   PDF (7490KB) ( 4 )   Lithium-sulfur (Li-S) battery is highly regarded as a promising next-generation energy storage device but suffers from sluggish sulfur redox kinetics. Probing the behavior and mechanism of the sulfur species on electrocatalytic surface is the first step to rationally introduce polysulfide electrocatalysts for kinetic pro-motion in a working battery. Herein, crystalline lithium sulfide (Li2S) is exclusively observed on electro-catalytic surface with uniform spherical morphology while Li2S on non-electrocatalytic surface is amorphous and irregular. Further characterization indicates the crystalline Li2S preferentially partici-pates in the discharge/charge process to render reduced interfacial resistance, high sulfur utilization, and activated sulfur redox reactions. Consequently, crystalline Li2S is proposed with thermodynamic and kinetic advantages to rationalize the superior performances of Li-S batteries. The evolution of solid Li2S on electrocatalytic surface not only addresses the polysulfide electrocatalysis strategy, but also inspires further investigation into the chemistry of energy-related processes.

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Dual redox catalysis of VN/nitrogen-doped graphene nanocomposites for high-performance lithium-sulfur batteries Erdong Jing, Liang Chen, Shoudong Xu, Wenzhi Tian, Ding Zhang, Nana Wang, Zhongchao Bai, Xianxian Zhou, Shibin Liu, Donghong Duan, Xiangyun Qiu 2022, 64(1): 574-582.  DOI: 10.1016/j.jechem.2021.05.015 Abstract ( 8 )   PDF (13861KB) ( 1 )   Lithium-sulfur (Li-S) batteries are regarded as one of the promising candidates for the next-generation energy storage system owing to their high capacity and energy density. However, the durable operation for the batteries is blocked by the shuttle behavior of soluble lithium polysulfides and the sluggish kinet-ics in the redox process. Here, VN nanoparticles on nitrogen-doped graphene (VN/NG) composite is syn-thesized by simple calcining method to modify the separators, which can not only chemically trap polysulfides, but also catalyze the conversion reaction between the polysulfides and the insoluble Li2S during the charge/discharge process. The catalytic effects of VN/NG are verified by the calculated activa-tion energy (Ea) , which is smaller than the counterpart with NG toward both directions of redox. Because of the synergistic adsorption-catalysis of VN/NG, the cells with VN/NG-modified separators deliver a superior rate performance (791 mAh g-1 at 5C) and cycling stability (863 mAh g-1 after 300 cycles with a low decaying rate of 0.068% per loop at 1C). This work provides a simple preparation strategy and fun-damental understanding of the bifunctional catalyst for high-performance Li-S batteries.

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Synthesis of PtCu-based nanocatalysts: Fundamentals and emerging challenges in energy conversion Wenjuan Yan, Dongpei Zhang, Quanxing Zhang, Yu Sun, Shuxia Zhang, Feng Du, Xin Jin 2022, 64(1): 583-606.  DOI: 10.1016/j.jechem.2021.05.003 Abstract ( 7 )   PDF (27750KB) ( 1 )   Proton exchange membrane fuel cell and direct methanol fuel cells have gained more attention due to high-energy density, remarkable conversion efficiency, and low emission. However, their widely practi-cal application was hindered by the high usage, limited sources, and high price of Pt catalysts. To achieve more cost-effective catalytic systems, PtCu-based multi-metallic nanoparticles are highly efficient for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). The incorporation of non-noble Cu metal can alter the properties of hybrids by forming new facets, planes, edges to promote the cleavage or formation of chemical bonds in catalytic reaction. This is a rapid growing area with numerous contributions from the interdisciplinary areas of nanocatalysis. This paper has summarized the recent progress in the past two years, in synthesizing PtCu-based alloys with various composition and morphologies, and critically discussed the effect of the catalyst preparation method, metal precursor, surfactant, reductant and heating temperature on nanostructure and electronic configuration. The impor-tant role of the composition, size, and morphology of PtCu bimetallic catalysts for electro oxidation reac-tions has been further established for structure-dependency studies. The challenges and perspectives of nanocatalysts for ORR and MOR discussed in this work is to provide further insights into rational design for cost-effective materials for energy.

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Novel polybenzimidazole/graphitic carbon nitride nanosheets composite membrane for the application of acid-alkaline amphoteric water electrolysis Bo Lv, Hang Yin, Zhigang Shao, Zoujie Luan, Ziyi Huang, Shucheng Sun, Yue Teng, Chunhui Miu, Qiang Gao 2022, 64(1): 607-614.  DOI: 10.1016/j.jechem.2021.05.009 Abstract ( 8 )   PDF (2859KB) ( 1 )   It is a great challenge to develop membrane materials with high performance and long durability for acid-alkaline amphoteric water electrolysis. Hence, the graphitic carbon nitride (g-C3N4) nanosheets were compounded with the (2,2'-m-phenylene) -5,5'-benzimidazole (m-PBI) matrix for the preparation of m-PBI/g-C3N4 composite membranes. The synthesis of g-C3N4 nanosheets and m-PBI matrix have been confirmed by X-ray diffraction (XRD) , scanning electron microscopy (SEM) , transmission electron micro-scoy (TEM) and 1H nuclear magnetic resonance spectra (1H NMR) , respectively. The fourier transform infrared spectroscopy (FT-IR) and SEM of the composite membranes showed the g-C3N4 nanosheets were good mechanical strength, and the TGA curves of m-PBI showed the high thermal stability of composite membranes. Besides, the m-PBI/g-C3N4 composite membrane showed excellent proton and hydroxide ion conductivity, which was higher than pure m-PBI and Nafion 115 membrane. The acid-alkaline ampho-teric water electrolysis test showed m-PBI/1% g-C3N4 composite membrane has the best performance with a current density of 800 mA cm-2 at cell voltage of 1.98 V at 20 °C. It showed that m-PBI/g-C3N4 composite membrane has a good application prospect for acid-alkaline amphoteric water electrolysis.

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Recent progress and perspectives on silicon anode: Synthesis and prelithiation for LIBs energy storage Yuanxing Zhang, Borong Wu, Ge Mu, Chengwei Ma, Daobin Mu, Feng Wu 2022, 64(1): 615-650.  DOI: 10.1016/j.jechem.2021.04.013 Abstract ( 11 )   PDF (18975KB) ( 8 )   The ever-increasing environmental/energy crisis as well as the rapid upgrading of mobile devices had stimulated intensive research attention on promising alternative energy storage and conversion devices. Among these devices, alkali metal ion batteries, such as lithium-ion batteries (LIBs) had attracted increas-ing research attention due to its several advantages including, environmental friendliness, high power density, long cycle life and excellent reversibility. It had been widely used in consumer electronics, elec-tric vehicles, and large power grids et ac. Silicon-based (silicon and their oxides, carbides) anodes had been widely studied. Its several advantages including low cost, high theoretical capacity, natural abun-dance, and environmental friendliness, which shows great potential as anodes of LIBs. In this review, we summarized the recently progress in the synthetic method of silicon matrix composites. The empirical method for prelithiation of silicon-based materials were also provided. Further, we also reviewed some novel characterization methods. Finally, the new design, preparation methods and properties of these nano materials were reviewed and compared. We hoped that this review can provide a general overview of recent progress and we briefly highlighted the current challenges and prospects, and will clarify the future trend of silicon anode LIBs research.