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2022, Vol. 66, No. 3　Online: 15 March 2022

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Green antisolvent additive engineering to improve the performance of perovskite solar cells Jiahui Li, Xiaodong Hua, Fei Gao, Xiaodong Ren, Chaoqun Zhang, Yu Han, Yuanrui Li, Bonan Shi, Shengzhong Liu 2022, 66(3): 1-8.  DOI: 10.1016/j.jechem.2021.06.023 Abstract ( 12 )   PDF (5793KB) ( 4 )   High-quality perovskite films with larger grain size and fewer defects is a prerequisite for highperformance perovskite solar cells (PSCs). Antisolvent-assisted crystallization is an effective approach to obtain compact and uniform perovskite films; however, the majority of antisolvents currently applied have strong toxicity, and the control of perovskite crystallization is not easy through single antisolvent. In this work, a green antisolvent of ethyl acetate (EA) with acetylacetone (AA) additive is used to fine-tune perovskite crystallization and passivate defect, which produces uniform and compact CH3NH3PbI3 perovskite films having larger grain and fewer grain boundaries and reduced defect density. Meanwhile, the interfacial hydrophobic characteristic of the perovskite films is enhanced. At the optimized concentration of AA in EA, the power conversion efficiency (PCE) of the CH3NH3PbI3 PSCs was improved from 19.2% to 21.1% and their stability in air was also enhanced. These results present a green antisolvent additive engineering strategy to enhance the crystallinity, passivate defects, and fabricate efficient and stable PSCs.

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Monitoring the morphology evolution of LiNi0.8Mn0.1Co0.1O2 during high-temperature solid state synthesis via in situ SEM Liang Tang, Xiaopeng Cheng, Rui Wu, Tianci Cao, Junxia Lu, Yuefei Zhang, Ze Zhang 2022, 66(3): 9-15.  DOI: 10.1016/j.jechem.2021.07.021 Abstract ( 5 )   PDF (6452KB) ( 5 )   The particle morphology determined by the sintering process is the director factor affecting the electro-chemical performance of Ni-rich NMC cathode materials. To prepare the ideal NMC particles, it is of great significance to understand the morphological changes during sintering process. In this work, the mor-phology evolution of LiNi0.8Mn0.1Co0.1O2 (NMC811) synthesis at temperature ranging from 300-1080 C were observed by in situ SEM. The uniform mixture of spherical Ni0.8Mn0.1Co0.1(OH)2 precursor and lithium sources (LiOH) was employed by high temperature solid-state process inside the SEM, which enables us to observe morphology changes in real time. The results show that synthetic reaction of LiNi0.8Mn0.1Co0.1O2 usually includes three processes: the raw materials' dehydration, oxidation, and com-bination, accompanied by a significant reduction in particle size, which is important reference to control the synthesis temperature. As heating temperature rise, the morphology of mixture also changed from flake to brick-shaped. However, Ni nanoparticle formation is apparent at higher temperature ~1000 C, suggesting a structural transformation from a layered to a rock-salt-like structure. Combining the in-situ observed changes in size and morphology, and with the premise of ensuring the morphology change from flakes to bricks, reducing the sintering temperature as much as possible to prevent excessive reduc-tion in particle size and layered to a rock-salt structure transformation is recommended for prepare ideal NMC particles.

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Revealing the role of mo doping in promoting oxygen reduction reaction performance of Pt3Co nanowires Zhiping Deng, Wanying Pang, Mingxing Gong, Zhehui Jin, Xiaolei Wang 2022, 66(3): 16-23.  DOI: 10.1016/j.jechem.2021.06.018 Abstract ( 13 )   PDF (5489KB) ( 3 )   Highly active and durable electrocatalysts towards oxygen reduction reaction (ORR) are imperative for the commercialization application of proton exchange membrane fuel cells. By manipulating ligand effect, structural control, and strain effect, we report here the precise preparation of Mo-doped Pt3Co alloy nanowires (Pt3Co-Mo NWs) as the efficient catalyst towards ORR with high specific activity (0.596 mA cm-2) and mass activity (MA, 0.84 A mg-1Pt), much higher than those of undoped counterparts. Besides activity, Pt3Co-Mo NWs also demonstrate excellent structural stability and cyclic durability even after 50,000 cycles, again surpassing control samples without Mo dopants. According to the strain maps and DFT calculations, Mo dopants could modify the electronic structure of both Pt and Co to achieve not only optimized oxygen-intermediate binding energy on the interface but also increased the vacancy forma-tion energy of Co, together leading to enhanced activity and durability. This work provides not only a facile methodology but also an in-depth investigation of the relationship between structure and properties to pro-vide general guidance for future design and optimization.

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Evaluation on a 400 Wh kg-1 lithium-sulfur pouch cell Ge Ye, Meng Zhao, Li-Peng Hou, Wei-Jing Chen, Xue-Qiang Zhang, Bo-Quan Li, Jia-Qi Huang 2022, 66(3): 24-29.  DOI: 10.1016/j.jechem.2021.07.010 Abstract ( 7 )   PDF (3908KB) ( 4 )   Lithium-sulfur (Li-S) batteries are highly regarded as next-generation energy storage devices due to their ultrahigh theoretical energy density of 2600 Wh kg-1. However, practical high-energy-density Li-S pouch cells suffer from limited cycling lifespan with rapid loss of active materials. Herein, systematic evaluation on a 400 Wh kg-1 Li-S pouch cell is carried out to reveal the working and failure mechanism of Li-S bat-teries under practical conditions. Electrode morphology, spatial distribution and species analysis of sul-fur, and capacity retention of electrodes are respectively evaluated after the first cycle of discharge or charge. Considerable lithium polysulfides are found in electrolyte even at the end of discharge or charge, where the sulfur redox reactions are reversible with high capacity retention. Meanwhile, severe morphol-ogy change is identified on lithium metal anode, yet there remains substantial active lithium to support the following cycles. This work not only demonstrates unique behaviors of Li-S batteries under practical conditions, which is essential for promoting the progress of Li-S pouch cells, but also affords a systematic evaluation methodology to guide further investigation on high-energy-density Li-S batteries.

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High-performance supercapacitors based on free-standing SiC@PEDOT nanowires with robust cycling stability Wenna Liu, Xiaoxiao Li, Weijun Li, Yumin Ye, Hong Wang, Peipei Su, Weiyou Yang, Ya Yang 2022, 66(3): 30-37.  DOI: 10.1016/j.jechem.2021.07.007 Abstract ( 5 )   PDF (10676KB) ( 1 )   Conductive polymers as one of the candidate materials with pseudocapacitor behavior have inspired wide attentions, because of their high conductivity, flexibility, low cost and excellent processability. However, the intrinsically poor cycling stability induced by the volume change over the doping/dedoping redox process limits their practical applications. Herein, we report the exploration of electrodes with robust cycling capacity for supercapacitors (SCs), which are rationally designed by coating conductive poly(3,4-ethylenedioxythiophene) (PEDOT) around free-standing SiC nanowires using an all-dry oxidative chemical vaper deposition (oCVD) method. The as-constructed SiC@PEDOT nanowire architecture enables a specific capacitance of 26.53 mF/cm2 at 0.2 mA/cm2, which is ~370% to that of SiC nanowire counterpart (7.04 mF/cm2). Moreover, their aqueous-based SCs exhibit robust cycling stability with 104% capacity retention after 10000 cycles, which is among the highest values achieved for PEDOT-based SCs.

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A graphitized expanded graphite cathode for aluminum-ion battery with excellent rate capability Xiaozhong Dong, Hao Chen, Haiwen Lai, Liyong Wang, Jiaqing Wang, Wenzhang Fang, Chao Gao 2022, 66(3): 38-44.  DOI: 10.1016/j.jechem.2021.07.016 Abstract ( 5 )   PDF (7576KB) ( 2 )   Aluminum-ion battery (AIB) is very promising for its safety and large current charge-discharge. However, it is challenging to build a high-performance AIB system based on low-cost materials especially cathode & electrolyte. Despite the low-cost expanded graphite-triethylaminehydrochloride (EG-ET) system has been improved in cycle performance, its rate capability still remains a gap with the expensive graphene-alkylimidazoliumchloride AIB system. In this work, we treated the cheap EG appropriately through an industrial high-temperature process, employed the obtained EG3K (treated at 3000 °C) cathode with AlCl3-ET electrolyte, and built a novel, high-rate capability and double-cheap AIB system. The new EG3K-ET system achieved the cathode capacity of average 110 mAh g-1 at 1 A g-1 with 18,000 cycles, and retained the cathode capacity of 100 mAh g-1 at 5 A g-1 with 27,500 cycles (fast charging of 72 s). Impressively, we demonstrated that a battery pack (EG3K-ET system, 12 mAh) had successfully driven the Model car running 100 m long. In addition, it was confirmed that the improvement of rate capability in the EG3K-ET system was mainly derived by deposition, and its capacity contribution ratio was about 53.7%. This work further promoted the application potential of the low-cost EG-ET AIB system.

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Beyond catalytic materials: Controlling local gas/liquid environment in the catalyst layer for CO2 electrolysis Zhuo Xing, Kaige Shi, Xun Hu, Xiaofeng Feng 2022, 66(3): 45-51.  DOI: 10.1016/j.jechem.2021.07.006 Abstract ( 8 )   PDF (4606KB) ( 3 )   Electrochemical reduction of CO2 to value-added chemicals using renewable electricity provides a promising strategy to achieve sustainable fuel production and carbon neutrality. Along with the development of electrocatalysts, flow cells with gas-diffusion electrodes (GDEs) have been used to reach commercially viable current densities for CO2 electrolysis, while the local environment and CO2 mass transport in the electrodes remain to be elucidated. In this review article, we highlight some insights into the microenvironment in the catalyst layer for CO2 electrolysis, including typical mass transport models for CO2 reduction in H-type cells and GDE flow cells, the effect of a hydrophobic microenvironment on CO2 mass transport and catalytic performance, and the formation of a gas/liquid balance and solid-liquid-gas interfaces for CO2 electrolysis. The insights and discussions in this article can provide important guidelines on the design of catalysts, electrodes, and electrolyzers for CO2 electrolysis, as well as other gas-involving electrocatalytic reactions.

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Efficient benzaldehyde photosynthesis coupling photocatalytic hydrogen evolution Juanjuan Luo, Lisong Chen, Jianlin Shi 2022, 66(3): 52-60.  DOI: 10.1016/j.jechem.2021.07.017 Abstract ( 8 )   PDF (10576KB) ( 5 )   Photosynthesis of organic compounds in coupling with promoted hydrogen evolution under mild conditions of light irradiation is considered as one of the most efficient and promising approach to obtain high purity hydrogen and value-added chemicals concurrently by utilizing green solar energy. Here, we report the synthesis of NiS nanoparticle-modified CdS nanorod composites (NiS/CdS) as an efficient bifunctional catalyst for the highly selective photocatalytic synthesis of high-value-added product benzaldehyde (BAD) from aqueous solution of benzyl alcohol (BA) under oxygen-free conditions, in accompanying with the efficient hydrogen evolution. The synergetic catalytic effect between NiS and CdS is proposed to play an important role in elevating the photo-redox performance. The composition-optimized 30% NiS/CdS catalyst affords an extraordinarily high H2 generation rate of 207.8 μmol h-1 and a simultaneous BAD generation rate of 163.8 μmol h-1 under visible light irradiation, which are respectively 139 and 950 times higher than those of CdS without NiS modification. To our knowledge, these are the highest photocatalytic production rates of both H2 and aldehyde ever reported on the concurrent photocatalytic of aldehyde synthesis and hydrogen evolution in green aqueous solution. This work provides a highly efficient photosynthesis strategy for the concurrent productions of high-value-added fine chemicals and hydrogen.

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Carbon dots regulate the interface electron transfer and catalytic kinetics of Pt-based alloys catalyst for highly efficient hydrogen oxidation Jie Wu, Yunjie Zhou, Haodong Nie, Kaiqiang Wei, Hui Huang, Fan Liao, Yang Liu, Mingwang Shao, Zhenhui Kang 2022, 66(3): 61-67.  DOI: 10.1016/j.jechem.2021.07.012 Abstract ( 6 )   PDF (10465KB) ( 1 )   The regulation of interface electron-transfer and catalytic kinetics is very important to design the efficient electrocatalyst for alkaline hydrogen oxidation reaction (HOR). Here, we show the Pt-Ni alloy nanoparticles (PtNi2) have an enhanced HOR activity compared with single component Pt catalyst. While, the interface electron-transfer kinetics of PtNi2 catalyst exhibits a very wide electron-transfer speed distribution. When combined with carbon dots (CDs), the interface charge transfer of PtNi2-CDs composite is optimized, and then the PtNi2-5 mg CDs exhibits about 2.67 times and 4.04 times higher mass and specific activity in 0.1 M KOH than that of 20% commercial Pt/C. In this system, CDs also contribute to trapping H+ and H2O generated during HOR, tuning hydrogen binding energy (HBE), and regulating interface electron transfer. This work provides a deep understanding of the interface catalytic kinetics of Pt-based alloys towards highly efficient HOR catalysts design.

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Compensating the impurities on the Cu surface by MOFs for enhanced hydrocarbon production in the electrochemical reduction of carbon dioxide Shin Joon Kang, Jong Ho Won, Hansaem Choi, Woohyeong Sim, Mun Kyoung Kim, Siraj Sultan, Youngkook Kwon, Hyung Mo Jeong 2022, 66(3): 68-73.  DOI: 10.1016/j.jechem.2021.06.031 Abstract ( 6 )   PDF (4211KB) ( 4 )   Copper (Cu) provides a cost-effective means of producing value-added fuels through the electrochemical reduction of carbon dioxide (CO2RR). However, we observed the production of hydrocarbons via CO2RR on commercial Cu films is less efficient because of the surface impurities, i.e., Fe. Carbon monoxide (CO), a reaction intermediate of CO2RR to hydrocarbons, binds strongly to the Fe sites and interrupts the production of hydrocarbons, resulting in an active hydrogen evolution reaction (HER). Herein, we report a method of blocking the effect of Fe impurities on the Cu surface through the preferential growth of nano-sized metal-organic frameworks (MOFs) on Fe site. When zirconium (Zr)-based MOFs (UiO-66) forms a compensating layer on Cu film via the terephthalic acid (TPA)-Fe coordination bond, the UiO-66 coated Cu film (UiO-66@Cu) presents significantly improved hydrocarbon Faradaic efficiency (FE) of 37.59% compared to 14.68% FE on commercial Cu film (99.9% purity) by suppressing HER. According to X-ray photoelectron spectroscopy (XPS) analysis, the UiO-66 ligand binds to entire metallic Fe site on the Cu surface, while metallic Cu is retained. Thus, UiO-66@Cu provides active sites of Cu for CO2RR and leads to highly efficient and selective production of hydrocarbons.

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Is machine learning redefining the perovskite solar cells? Nishi Parikh, Meera Karamta, Neha Yadav, Mohammad Mahdi Tavakoli, Daniel Prochowicz, SeckinAkin, Abul Kalam, Soumitra Satapathi, Pankaj Yadav 2022, 66(3): 74-90.  DOI: 10.1016/j.jechem.2021.07.020 Abstract ( 5 )   PDF (9302KB) ( 4 )   Development of novel materials with desirable properties remains at the forefront of modern scientific research. Machine learning (ML), a branch of artificial intelligence, has recently emerged as a powerful technology in optoelectronic devices for the prediction of various properties and rational design of materials. Metal halide perovskites (MHPs) have been at the centre of attraction owing to their outstanding photophysical properties and rapid development in solar cell application. Therefore, the application of ML in the field of MHPs is also getting much attention to optimize the fabrication process and reduce the cost of processing. Here, we comprehensively reviewed different applications of ML in the designing of both MHP absorber layers as well as complete perovskite solar cells (PSCs). At the end, the challenges of ML along with the possible future direction of research are discussed. We believe that this review becomes an indispensable roadmap for optimizing materials composition and predicting design strategies in the field of perovskite technology in the future.

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Nano storage-boxes constructed by the vertical growth of MoS2 on graphene for high-performance Li-S batteries Bowen Cui, Xiaomin Cai, Wenqiang Wang, Petr Saha, Gengchao Wang 2022, 66(3): 91-99.  DOI: 10.1016/j.jechem.2021.06.035 Abstract ( 7 )   PDF (8837KB) ( 2 )   In order to accelerate the reaction kinetics of lithium-sulfur batteries, the introduction of electro catalysis and proper structural control of the sulfur cathode is urgently needed. MoS2 nano sheets was selectively grown vertically (V-MoS2) on the microwave-reduced graphene (rGO) sheets through chemical coupling to construct a self-supporting sulfur cathode with a nano storage-box structure (V-MoS2 as the wall and rGO as the bottom). RGO, which has a high conductivity of 37 S cm-1, greatly accelerates the transfer of electrons from the active sites on the edge of the layer to the solution. The introduction of carbon tubes can connect the abundant pores in the foam and act as a long-range conductive path. The 2D-orthogonal-2D structure maximally exposes the edge active sites of MoS2, and together with graphene form a nano reactor of sulfur, intermediate lithium polysulfides and discharge product Li2S(2). The effective combination of the microstructure confinement of the nano storage-boxes and the efficient synchronous catalytic mechanism of V-MoS2 greatly improves the electrochemical performance of the lithium-sulfur batteries. As a result, the assembled lithium-sulfur battery displays a high initial discharge capacity of 1379 mAh g-1, good cycle stability (86% capacity retention after 500 cycles at 0.1C) and superior rate performance.

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One-pot synthesis of FeNxC as efficient catalyst for high-performance zinc-air battery Yang Li, Kuanda Xu, Qi Zhang, Zhi Zheng, Shunning Li, Qinghe Zhao, Can Li, Cheng Dong, Zongwei Mei, Feng Pan, Shixue Dou 2022, 66(3): 100-106.  DOI: 10.1016/j.jechem.2021.07.009 Abstract ( 9 )   PDF (4676KB) ( 2 )   Rechargeable zinc-air batteries (ZAB) with a high theoretical energy density of 1086 Wh kg-1, have received tremendous research attention. However, the practical application of ZABs is still limited by high polarization and poor energy efficiency (low power density) due to the sluggish 4 electrons (e-)/oxygen (O2) kinetics over the air electrode. Here, a noble-metal-free FeNxC electrocatalyst is developed via a one-pot approach, which provides a high density of the oxygen reduction reaction (ORR) active site and facilitates the ORR kinetics. Accordingly, the as-assembled Zn-air battery displayed a low charge-discharge voltage gap of 0.71 V at 10 mA cm-2, a remarkable peak power density as high as 181.2 mW cm-2, as well as the long-term durability for hundreds of hours, among the top level of those reported previously. Our work provides a major boost for the practical application of Zn-air battery in the future.

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Recent advances in alkaline hydrogen oxidation reaction Lixin Su, Dan Gong, Yiming Jin, Dean Wu, Wei Luo 2022, 66(3): 107-122.  DOI: 10.1016/j.jechem.2021.07.015 Abstract ( 6 )   PDF (17155KB) ( 1 )   The development of highly efficient electrocatalysts toward hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cells (AEMFCs). However, the HOR kinetics in alkaline is two to three orders of magnitude slower than that in acid. More critically, fundamental understanding of the sluggish kinetics derived from the pH effect is still debatable. In this review, the recent development of understanding HOR mechanism and rational design of advanced HOR electrocatalysts are summarized. First, recent advances in the theories focusing on fundamental understandings of HOR under alkaline electrolyte are comprehensively discussed. Then, from the aspect of intermediates binding energy, optimizing hydrogen binding energy (HBE) and increasing hydroxyl binding energy (OHBE), the strategies for designing efficient alkaline HOR catalysts are summarized. At last, perspectives for the future research on alkaline HOR are pointed out.

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Urea-assisted mixed gas treatment on Li-Rich layered oxide with enhanced electrochemical performance Liying Bao, Lei Wei, Nuoting Fu, Jinyang Dong, Lai Chen, Yuefeng Su, Ning Li, Yun Lu, Yongjian Li, Shi Chen, Feng Wu 2022, 66(3): 123-132.  DOI: 10.1016/j.jechem.2021.07.023 Abstract ( 6 )   PDF (10761KB) ( 1 )   Lithium-rich manganese-based oxides (LRMOs) have been considered as one of the most promising cathode materials owing to their superior specific capacity and high operating voltage. However, their large-scale commercial applications are limited due to problems such as structural instability, voltage decay, and poor cycle stability. Herein, pre-generated oxygen vacancies and oxygen-deficient phase were introduced to Li1.2Mn0.6Ni0.2O2 (LMNO) using a facile urea-assisted mixed gas treatment (UMGT) method for facilitating electronic and ionic conductivity, reducing the surface oxygen partial pressure, and suppressing the release of lattice oxygen. Compared with the pristine LMNO material, the UMGT sample modified at 200 °C exhibited enhanced discharge capacity, capacity retention, and rate capability. In addition, the Li+ diffusion coefficient significantly improved by 50% than that of the reference LMNO. More importantly, the voltage decay was effectively suppressed, with average potential decreasing from 0.53 V (LMNO) to 0.39 V (UMGT-200) after 200 cycles at 1 C. The proposed UMGT method provides an effective strategy to alleviate the phase transition and improve the electrochemical performance for lithium-rich materials, and identifies a promising research direction to inhibit the voltage decay of layered anion redox cathode materials.

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Stabilizing sodium metal anode through facile construction of organic-metal interface Jiaolong Zhang, Shuo Wang, Wenhui Wang, Baohua Li 2022, 66(3): 133-139.  DOI: 10.1016/j.jechem.2021.07.022 Abstract ( 10 )   PDF (7544KB) ( 11 )   Implementation of sodium metal anode is highly desired for sodium batteries due to its high theoretical capacity and low redox potential. Unfortunately, formation of unstable solid electrolyte interphase (SEI) and uncontrollable growth of dendrites during charge/discharge cycles greatly hinder the practical application of sodium metal anode. In this study, an organic-metal artificial layer made of PVdF and Bi was constructed to protect Cu current collector via a facile coating method, leading to smooth and dense sodium plating/stripping, which in retern enables stable cycling and high coulombic efficiency (CE). At 1 mA cm-2, PB@Cu current collector presents extended lifetime of ~2500 h with high sodium utilization of 50%, which is approximately six times higher than Cu current collector. PB@Cu electrode also displays high average CE of 99.92% and 99.95% over 2500 and 1300 cycles at 1 and 2 mA cm-2 respectively, which is in sharp contrast to the low and tremendously fluctuant CE gained from bare Cu electrode. Moreover, stable capacity of > 90 mAh g-1 over 150 cycles is realized for PB@Cu-based full cell assembled with NVP cathode at a low negative-positive capacity ratio of ~3.5, which is significantly higher than 37.2 mAh g-1 obtained from NVP/Cu at 150th cycle. The superior electrochemical performance of PB@Cu current collector is revealed to originate from the alloyed Na3Bi phase with high sodium conductivity and robust mechanical strength as well as the formation of NaF-rich SEI with fast sodium ion migration, which enable dendrite-free morphology during plating/stripping cycles.

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Monoclinic Cu3(OH)2V2O7·2H2O nanobelts/reduced graphene oxide: A novel high-capacity and long-life composite for potassium-ion battery anodes Liming Ling, Xiwen Wang, Yu Li, Chenxiao Lin, Dong Xie, Min Zhang, Yan Zhang, Jinjia Wei, Huajie Xu, Faliang Cheng, Chuan Wu, Shiguo Zhang 2022, 66(3): 140-151.  DOI: 10.1016/j.jechem.2021.07.025 Abstract ( 8 )   PDF (22277KB) ( 1 )   Developing suitable anode materials for potassium-ion batteries (PIBs) remains a great challenge owing to the limited theoretical capacity of active materials and large radius of K+ ion (1.38 Å). To solve these obstacles, by integrating the principles of multielectron transfer and rational porous crystal framework, we creatively propose the monoclinic Cu3(OH)2V2O7·2H2O (CVO) as a novel anode for PIBs. Furthermore, inspired by the metastable nature of CVO under high temperature/pressure, we skillfully design a facile hydrothermal recrystallization strategy without the phase change and surfactants addition. Thus, for the first time, the porous composite of Cu3(OH)2V2O7·2H2O nanobelts covered in situ by reduced graphene oxide (CVO NBs/rGO) was assembled, greatly improving the deficiencies of CVO. When used as a novel anode for PIBs, CVO NBs/rGO delivers large specific capacity (up to 551.4 mAh g-1 at 50 mA g-1), high-rate capability (215.3 mAh g-1 at 2.5 A g-1) and super durability (203.6 mAh g-1 at 500 mA g-1 even after 1000 cycles). The outstanding performance can be ascribed to the synergistic merits of desirable structural features of monoclinic CVO nanobelts and the highly conductive graphene 3D network, thus promoting the composite material stability and electrical/ionic conductivity. This work reveals a novel metal vanadate-based anode material for PIBs, would further motivate the subsequent batteries research on M3(OH)2V2O7·nH2O (M; Co, Ni, Cu, Zn), and ultimately expands valuable fundamental understanding on designing other high-performance electrode materials, including the combined strategies of multielectron transfer with rational porous crystal framework, and the composite fabrication of 1D electrode nanostructure with conductive carbon matrix.

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Excess PbI2 evolution for triple-cation based perovskite solar cells with 21.9% efficiency Zhu Ma, Dejun Huang, Qianyu Liu, Guangyuan Yan, Zheng Xiao, Dong Chen, Jiaxuan Zhao, Yan Xiang, Changtao Peng, Haijin Li, Meng Zhang, Wenfeng Zhang, Lianfeng Duan, Yuelong Huang 2022, 66(3): 152-160.  DOI: 10.1016/j.jechem.2021.07.030 Abstract ( 11 )   PDF (8539KB) ( 4 )   The triple cation mixed perovskites (CsFAMA) are known as one of the most efficient candidates for perovskite solar cells (PSCs). It is found that the power conversion efficiency (PCE) of triple-cation based devices would increase with the test time extending, and the maximum efficiency is normally obtained after several days aging storage. Here, the relationship between enhanced device performance, excess PbI2 and its evolution in triple cation perovskite films of initial days was systematically explored. The CsFAMA-PSCs are prepared by two-step methods under two environmental conditions, including in the glove box and the ambient air (30% humidity). After 7 days testing, the maximum PCE of PSCs under two conditions dramatically increased 12.4% and 12.2%, reached 21.68% and 21.89%, respectively. At initial days, the XRD peak intensities of perovskite phase gradually decreased and those corresponding to PbI2 increased. Along with time-resolved photoluminescence (TRPL) and kelvin probe force microscopy (KPFM), it was found that the defects were passivated with the evolution of PbI2. This work reveals the excess PbI2 and its evolution in perovskite film, which can further supplement the understanding of PbI2 defect passivation.

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Reversible lithium storage in sp2 hydrocarbon frameworks Zhangxiang Hao, Yiyun Liu, Liqun Kang, Bolun Wang, Junwen Gu, Lin Sheng, Ruoyu Xu, Sushila Marlow, Dan J.L. Brett, Yunhui Huang, Feng Ryan Wang 2022, 66(3): 161-167.  DOI: 10.1016/j.jechem.2021.07.019 Abstract ( 5 )   PDF (2917KB) ( 3 )   Polymer materials offer controllable structure-dependent performances in separation, catalysis and drug release. Their molecular structures can be precisely tailored to accept Li+ for energy storage applications. Here the design of sp2 carbon-based polyphenylene (PPH) with high lithium-ion uptakes and long-term stability is reported. Linear-PPH (L-PPH) exceeds the performance of crosslink-PPH (C-PPH), due to the fact that it has an ordered lamellar structure, promoting the Li+ intercalation/deintercalation channel. The L-PPH cell shows a clear charge and discharge plateau at 0.35 and 0.15 V vs. Li+/Li, respectively, which is absent in the C-PPH cell. The Li+ storage capacity of L-PPH is five times that of the C-PPH. The reversible storage capacity is further improved to 261 mAh g-1 by functionalizing the L-PPH with the -SO3H groups. In addition, the Li-intercalated structures of C-PPH and L-PPH are investigated via near-edge X-ray absorption fine structure (NEXAFS), suggesting the high reversible Li+ -CC bond interaction at L-PPH. This strategy, based on new insight into sp2 functional groups, is the first step toward a molecular understanding of the structure storage-capacity relationship in sp2 carbon-based polymer.

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PtRu nanoparticles supported on noble carbons for ethanol electrooxidation Alberto Rodríguez-Gómez, Enrico Lepre, Luz Sánchez-Silva, Nieves López-Salas, Ana Raquel dela Osa 2022, 66(3): 168-180.  DOI: 10.1016/j.jechem.2021.07.004 Abstract ( 5 )   PDF (5321KB) ( 2 )   In this work, three cytosine derived nitrogen doped carbonaceous materials (noble carbons, NCs) with different atomic C/N ratios and porous networks have been synthesized and used as supports for PtRu electrocatalysts in the ethanol oxidation reaction (EOR) for clean hydrogen production. Both, the metal phase and the carbon support play critical roles in the electrocatalysts final performance. Lower NPs size distribution was obtained over supports with low atomic C/N ratios (i.e., 4 and 6) and defined porosity (i.e., 1701 m2 g-1 for PtRu/CNZ and 1834 m2 g-1 for PtRu/CLZ, respectively). In contrast, a lower C/N ratio and poor porous network (i.e., 65 m2 g-1, PtRu/CLK) led to the largest particle size and fostered an increase of the alloying degree between Pt and Ru NPs (i.e., 3% for C/N ~ 6 and 28% for C/N ~ 3). Electrochemical active surface area was found to increase with decreasing NPs size and the alloy extent, due to a higher availability of Pt active sites. Accelerated degradation tests showed that PtRu/NCs outperform similar to PtRu NPs on commercial carbon pointing at the stabilizing effect of NCs. PtRu/CNZ exhibited the best electrochemical performance (i.e., 69.1 mA mgPt-1), outperforming PtRu/CLZ and PtRu/CLK by 3-and 9-fold, respectively, due to a suitable compromise between particle sizes, degree of alloy, textural properties and elemental composition. Best anodes were scaled-up to a proton exchange membrane cell and PtRu/CNZ was proved to provide the best electrocatalytic activity (262 mA cm-2 and low energy requirements), matching the values obtained by the state of the art of EOR electrocatalysts.

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Dimethoxymethane production via CO2 hydrogenation in methanol over novel Ru based hierarchical BEA Waqar Ahmad, Fan Liang Chan, Abhijit Shrotri, Yayati Naresh Palai, Huanting Wang, Akshat Tanksale 2022, 66(3): 181-189.  DOI: 10.1016/j.jechem.2021.07.026 Abstract ( 5 )   PDF (5719KB) ( 3 )   Dimethoxymethane (DMM), a diesel blend fuel, is being researched with high interest recently due to its unique fuel properties. It is commercially produced via a two step-process of methanol oxidation to make formaldehyde, followed by its condensation with methanol. This study presents a one-pot method of DMM synthesis from methanol mediated carbon dioxide hydrogenation over novel heterogeneous catalysts. The effect of catalyst pore structure was investigated by synthesizing 3 wt% Ru over novel hierarchical zeolite beta (HBEASX) and comparing against Ru doped commercial zeolite beta (CBEA) and desilicated hierarchical zeolite beta (HBZDS). The results showed that 3%Ru/HBEASX provided the best activity for DMM production due to its large average pore size. It also showed the decisive role of SiO2/Al2O3 molar ratio, with SiO2/Al2O3 = 75 providing the highest DMM yield of 13.2 mmol/gcat.LMeOH with ca. 100% selectivity. The activity of 3%Ru/HBEAS3 after 5 recycle steps demonstrated the reusability of this catalyst.

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A dual-bed catalyst for producing ethylene and propylene from syngas YoumingNi, Zhaopeng Liu, Peng Tian, Zhiyang Chen, Yi Fu, Wenliang Zhu, Zhongmin Liu 2022, 66(3): 190-194.  DOI: 10.1016/j.jechem.2021.08.002 Abstract ( 3 )   PDF (605KB) ( 2 )

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Interconnected carbon nanocapsules with high N/S co-doping as stable and high-capacity potassium-ion battery anode Honghui Bi, Xiaojun He, Lei Yang, Hongqiang Li, Biyu Jin, Jieshan Qiu 2022, 66(3): 195-204.  DOI: 10.1016/j.jechem.2021.08.016 Abstract ( 9 )   PDF (16644KB) ( 3 )   Carbonaceous materials have drawn much attention in potassium-ion batteries (PIBs) due to their low price and superior physicochemical properties. However, the application of carbonaceous materials in PIB anodes is hindered by sluggish kinetics and large volume expansion. Herein, N/S co-doped carbon nanocapsule (NSCN) is constructed for superior K+ storage. The NSCN possesses 3D nanocapsule framework with abundant meso/macropores, which guarantees structural robustness and accelerates ions/electrons transportation. The high-level N/S co-doping in carbon matrix not only generates ample defects and active sites for K+ adsorption, but also expands interlayer distance for facile K+ intercalation/deintercalation. As a result, the NSCN electrode delivers a high reversible capacity (408 mAh g-1 at 0.05 A g-1), outstanding rate capability (149 mAh g-1 at 5 A g-1) and favorable cycle stability (150 mAh g-1 at 2 A g-1 after 2000 cycles). Ex situ TEM, Raman and XPS measurements demonstrate the excellent stability and reversibility of NSCN electrode during potassiation/depotassiation process. This work provides inspiration for the optimization of energy storage materials by structure and doping engineering.

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Tuning crystal orientation and charge transport of quasi-2D perovskites via halogen-substituted benzylammonium for efficient solar cells Guiqiang Cheng, Jian Wang, Rong Yang, Cheng Li, Hao Zhang, Nana Wang, Renzhi Li, Jianpu Wang, Wei Huang 2022, 66(3): 205-209.  DOI: 10.1016/j.jechem.2021.07.033 Abstract ( 5 )   PDF (5431KB) ( 2 )   Quasi-two-dimensional (quasi-2D) perovskites with high stability usually suffers from poor device efficiency. Chemical tuning of the spacer cations has been an effective strategy to achieve efficient and stable quasi-2D perovskite solar cells. Here, we demonstrate that 3-halogon-substituted benzylammonium iodide (3X-BAI, X = F, Cl, Br, I) can significantly affect the orientation of low-dimensional perovskites and charge transport from perovskite to hole extraction layer, as well as device performance. With 3Br-BAI, we achieve the highest device efficiency of 13.21% for quasi-2D perovskites with a nominal n = 3 average composition. Our work provides a facile approach to regulate vertical crystal orientation and charge transport via tuning the molecular structure of organic spacer toward high performance quasi-2D perovskite solar cells.

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Coupling CO2 reduction with ethane aromatization for enhancing catalytic stability of iron-modified ZSM-5 Zhenhua Xie, Elaine Gomez, Dong Wang, Ji Hoon Lee, Tiefeng Wang, Jingguang G. Chen 2022, 66(3): 210-217.  DOI: 10.1016/j.jechem.2021.08.005 Abstract ( 5 )   PDF (7341KB) ( 2 )   The shale gas revolution and the carbon-neutrality goal are motivating the landscape toward the synthesis of value-added chemicals or fuels from underutilized ethane with the assistance of greenhouse gas CO2. Combining ethane aromatization with CO2 reduction offers an opportunity to directly produce liquid products for facile separation, storage, and transportation. In the present work, Fe/ZSM-5 catalysts showed promise in the simultaneous CO2 reduction and ethane aromatization at atmospheric pressure and 873 K. The catalysts were further investigated using X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) measurements under in-situ conditions, indicating that most of Fe species existed in the form of Fe oxides and a portion of Fe was incorporated into the ZSM-5 framework generating Lewis acid sites. Both types of Fe species remained almost unchanged under reaction conditions, contributing to an enhanced aromatization activity of Fe/ZSM-5. The effects of CO2 and steam on the acid sites and in turn aromatization activity were also investigated by transient studies, which exhibited a reversible modification behavior. Moreover, CO2 was identified to be critical to enhance coke resistance and in turn catalyst stability. This work highlights the feasibility of using CO2 to assist the upgrading of abundant ethane from shale gas to aromatics over non-precious Fe-based zeolite catalysts.

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Effects of silver-doping on properties of Cu(In,Ga)Se2 films prepared by CuInGa precursors Chen Wang, Daming Zhuang, Ming Zhao, YuxianLi, Liangzheng Dong, Hanpeng Wang, Jinquan Wei, Qianming Gong 2022, 66(3): 218-225.  DOI: 10.1016/j.jechem.2021.08.008 Abstract ( 3 )   PDF (2766KB) ( 2 )   The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target. The precursors are selenized in the H2Se-containing atmosphere to prepare (Ag,Cu)(In,Ga)Se2 (ACIGS) absorbers. The beneficial effects of Ag doping are demonstrated and their mechanism is explained. It is found that Ag doping significantly improves the films crystallinity. This is believed to be due to the lower melting point of chalcopyrite phase obtained by the Ag doping. This leads to a higher migration ability of the atoms that in turn promotes grain boundary migration and improves the film crystallinity. The Ga enrichment at the interface between the absorber and the back electrode is also alleviated during the selenization annealing. It is found that Ag doping within a specific range can passivate the band tail and improve the quality of the films. Therefore, carrier recombination is reduced and carrier transport is improved. The negative effects of excessive Ag are also demonstrated and their origin is revealed. Because the atomic size of Ag is different from that of Cu, for the Ag/(Ag + Cu) ratio (AAC) ≥ 0.030, lattice distortion is aggravated, and significant micro-strain appears. The atomic radius of Ag is close to those of In and Ga, so that the continued increase in AAC will give rise to the AgIn or AgGa defects. Both the structural and compositional defects degrade the quality of the absorbers and the device performance. An excellent absorber can be obtained at AAC of 0.015.

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Inhomogeneous lithium-storage reaction triggering the inefficiency of all-solid-state batteries Jaeyoung Kim, Wontae Lee, Jangwhan Seok, Eunkang Lee, Woosung Choi, Hyunyoung Park, Soyeong Yun, Minji Kim, Jun Lim, Won-Sub Yoon 2022, 66(3): 226-236.  DOI: 10.1016/j.jechem.2021.08.017 Abstract ( 21 )   PDF (12026KB) ( 12 )   All-solid-state batteries offer an attractive option for developing safe lithium-ion batteries. Among the various solid-state electrolyte candidates for their applications, sulfide solid electrolytes are the most suitable owing to their high ionic conductivity and facile processability. However, their performance is extensively lower compared with those of conventional liquid electrolyte-based batteries mainly because of interfacial reactions between the solid electrolytes and high capacity cathodes. Moreover, the kinetic evolution reaction in the composite cathode of all-solid-state lithium batteries has not been actively discussed. Here, electrochemical analyses were performed to investigate the differences between the organic liquid electrolyte-based battery and all-solid-state battery systems. Combined with electrochemical analyses and synchrotron-based in situ and ex situ X-ray analyses, it was confirmed that inhomogeneous reactions were due to physical contact. Loosely contacted and/or isolated active material particles account for the inhomogeneously charged regions, which further intensify the inhomogeneous reactions during extended cycles, thereby increasing the polarization of the system. This study highlighted the benefits of electrochemo-mechanical integrity for securing a smooth conduction pathway and the development of a reliable homogeneous reaction system for the success of solid-state batteries.

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Highly active cobalt-doped nickel sulfide porous nanocones for high-performance quasi-solid-state zinc-ion batteries Xin Tong, Yun Li, Ning Pang, Yang Zhou, Dajun Wu, Dayuan Xiong, Shaohui Xu, Lianwei Wang, Paul K. Chu 2022, 66(3): 237-249.  DOI: 10.1016/j.jechem.2021.08.020 Abstract ( 3 )   PDF (15655KB) ( 2 )   Flexible quasi-solid zinc-ion batteries (ZIBs) have large potential in power applications due to the low price, wearable nature, safety, and high capacity. However, the use of transition metal sulfide cathodes in ZIBs has not been studied extensively and the underlying mechanism and theoretical basis of this type of batteries are not well understood. Herein, a highly active cobalt-doped Ni3S2 porous nanocone framework (C12NS) is designed and demonstrated as a zinc-ion battery electrode. First-principles calculation and experiments reveal that the cobalt dopant improves the battery properties greatly. The assembled flexible zinc-ion battery exhibits a high specific capacity of 453.3 mAh g-1 at a current density of 0.4 A g-1 in as well as excellent cycling stability as manifested by a capacity retention ratio of 89.5% at a current density of 4 A g-1 after 5000 cycles. The peak energy density of 553.9 Wh kg-1 is also superior to those of most recently reported NiCo-based zinc-ion batteries. More importantly, the flexible battery can be operated under severe mechanical bending and even continues to work after physical puncturing without showing leakage. These exciting results not only reveal a novel design of cathode materials for zinc-based batteries, but also suggest their immense commercial potential in portable and wearable electronics.

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Synergy of mesoporous SnO2 and RbF modification for high-efficiency and stable perovskite solar cells Qian Chen, Changtao Peng, Lin Du, Tian Hou, Wenjing Yu, Dong Chen, Hui Shu, Dejun Huang, Xiangqing Zhou, Jinyang Zhang, Wenfeng Zhang, Haijin Li, Jiale Xie, Yuelong Huang 2022, 66(3): 250-259.  DOI: 10.1016/j.jechem.2021.08.014 Abstract ( 8 )   PDF (7142KB) ( 5 )   Electron transport layer (ETL) is very critical to the performance of perovskite solar cells (PSCs), and optimization work on ETL has received extensive attentions especially on tin oxide (SnO2) since it is an excellent ETL material widely applied in high-efficiency PSCs. Thereinto, introducing mesoporous structure and surface modification are two important approaches which are commonly applied. Herein, based on the previous work in low-temperature fabrication process of mesoporous SnO2 (m-SnO2), we introduced a modification process with rubidium fluoride (RbF) to the m-SnO2 ETL, and successfully achieved a synergy of the m-SnO2 and RbF modification: not only the shortcoming of the m-SnO2 in interfacial traps was overcome, but also the carrier collection efficiency was further improved. The PSCs based on the m-SnO2 ETL with RbF modification demonstrated outstanding performances: a champion power conversion efficiency (PCE) of 22.72% and a stability performance of maintaining 90% of the initial PCE after 300 h of MPP tracking were obtained without surface passivation of perovskite film. Hence, utilizing the abovementioned synergy is a cost-effective and feasible strategy for fabricating high-efficiency and stable PSCs since the fabrication process of the m-SnO2 ETL is a kind of low temperature process and RbF is cheap.

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Status and challenges facing representative anode materials for rechargeable lithium batteries Liqiang Zhang, Chenxi Zhu, Sicheng Yu, Daohan Ge, Haoshen Zhou 2022, 66(3): 260-294.  DOI: 10.1016/j.jechem.2021.08.001 Abstract ( 15 )   PDF (14357KB) ( 6 )   Rechargeable lithium batteries have been widely regarded as a revolutionary technology to store renewable energy sources and extensively researched in the recent several decades. As an indispensable part of lithium batteries, the evolution of anode materials has significantly promoted the development of lithium batteries. However, since conventional lithium batteries with graphite anodes cannot meet the ever-increasing demands in different application scenarios (such as electric vehicles and large-scale power supplies) which require high energy/power density and long cycle life, various improvement strategies and alternative anode materials have been exploited for better electrochemical performance. In this review, we detailedly introduced the characteristics and challenges of four representative anode materials for rechargeable lithium batteries, including graphite, Li4Ti5O12, silicon, and lithium metal. And some of the latest advances are summarized, which mainly contain the modification strategies of anode materials and partially involve the optimization of electrode/electrolyte interface. Finally, we make the conclusive comments and perspectives, and draw a development timeline on the four anode materials. This review aims to offer a good primer for newcomers in the lithium battery field and benefit the structure and material design of anodes for advanced rechargeable lithium batteries in the future.

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In vacuo XPS investigation of surface engineering for lithium metal anodes with plasma treatment Bo Zhao, Jin Li, Maxime Guillaume, Jolien Dendooven, Christophe Detavernier 2022, 66(3): 295-305.  DOI: 10.1016/j.jechem.2021.08.032 Abstract ( 13 )   PDF (10604KB) ( 5 )   Lithium (Li) metal is an attractive anode material with high capacity (3860 mAh g-1) and low potential (-3.04 V vs. standard hydrogen electrode) that shows highly promising for applications requiring high energy density. However, the low electrochemical potential of Li metal makes it extremely reactive and inevitably forming a native oxidized layer in the ambient environment and repeatedly being consumed when exposed to liquid electrolytes. It is therefore beneficial to replace the poorly controlled native passivation layer with a tailored artificial SEI to improve interface management between Li and electrolyte and enhance the stability of Li metal battery. Here, we use an integrated glovebox-atomic layer deposition (ALD)-X-ray photoelectron spectroscopy (XPS) setup to in-situ investigating the pristine Li surface and the surface composition after Ar, H2, O2, N2 and NH3 plasma treatment processes. We find that the pristine Li foil is naturally being covered with a native oxidized layer, which is mainly composed of LiOH, Li2O and Li2CO3. These investigated plasmas can efficiently remove the oxidized layer from the Li metal surface, in which metallic Li surface is obtained after Ar or H2 plasma treatments, where Ar plasma is more efficient. While O2 plasma treatment produces a Li2O layer, and N2 or NH3 plasma treatment leads to a Li3N (including a certain amount of LiON) layer on the Li surface. When employing the representative metallic Li (by Ar plasma treatment), Li2O layer coated Li (by O2 plasma treatment) and Li3N layer coated Li (by N2 plasma treatment) foils as electrodes in symmetric Li metal batteries, the Li3N coated Li electrode exhibits much higher stability than that of metallic and Li2O layer coated Li foils. Improved electrochemical performance has also been achieved in LiMn2O4 (LMO)||Li full cells using Li anode with Li3N protective coating layer. Our work reveals the detailed process of surface engineering of Li metal anodes with plasma treatments by in vacuo XPS, which may also be extended to other gas-treatment or plasma-treatment for stabilization of high energy density Li metal anodes and other metal-based anodes.

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Metal-organic framework-derived carbon nanotubes with multi-active Fe-N/Fe sites as a bifunctional electrocatalyst for zinc-air battery Chao Yang, Shanshan Shang, Qinfen Gu, Jin Shang, Xiao-yan Li 2022, 66(3): 306-313.  DOI: 10.1016/j.jechem.2021.08.019 Abstract ( 6 )   PDF (8578KB) ( 3 )   Sustainable metal-air batteries demand high-efficiency, environmentally-friendly, and non-precious metal-based electrocatalysts with bifunctionality for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this research, novel functional carbon nanotubes with multi-active sites including well-dispersed single-atom iron throughout the walls and encapsulated ultrafine iron nanoparticles were synthesized as an electrocatalyst (FeNP@Fe-N-C) through one-step pyrolysis of metal-organic frameworks. High-resolution synchrotron powder X-ray diffraction and X-ray absorption spectroscopy were applied to characterize the unique structure of the electrocatalyst. In comparison to the commercial Pt/C and RuO2 electrodes, the newly prepared FeNP@Fe-N-C presented a superb bifunctional performance with its narrow potential difference (Egap) of 0.73 V, which is ascribed to the metallic Fe nanoparticles that boosts the adsorption and activation of oxygen on the active sites with an enhanced O2 adsorption capacity of 7.88 cm3 g-1 and synergistically functionalizes the iron atoms dispersed on the nanotubes. A rechargeable zinc-air battery based on FeNP@Fe-N-C exhibited a superior open-circuit voltage (1.45 V), power density (106.5 mW cm-2), and stable cycling performance. The green technique developed in this work for the fabrication of functional nanotubes raises the prospect of making more efficient electrocatalysts for sustainable energy cells.

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Perovskite-type lanthanum ferrite based photocatalysts: Preparation, properties, and applications Muhammad Humayun, Habib Ullah, Muhammad Usman, Aziz Habibi-Yangjeh, Asif Ali Tahir, Chundong Wang, Wei Luo 2022, 66(3): 314-338.  DOI: 10.1016/j.jechem.2021.08.023 Abstract ( 40 )   PDF (28667KB) ( 26 )   Clean energy and a sustainable environment are grand challenges that the world is facing which can be addressed by converting solar energy into transportable and storable fuels (chemical fuel). The main scientific and technological challenges for efficient solar energy conversion, energy storage, and environmental applications are the stability, durability, and performance of low-cost functional materials. Among different nanomaterials, perovskite type LaFeO3 has been extensively investigated as a photocatalyst due to its abundance, high stability, compositional and structural flexibility, high electrocatalytic activity, efficient sunlight absorption, and tunable band gap and band edges. Hence, it is urgent to write a comprehensive review to highlight the trend, challenges, and prospects of LaFeO3 in the field of photocatalytic solar energy conversion and environment purification. This critical review summarizes the history and basic principles of photocatalysis. Further, it reviews in detail the LaFeO3, applications, shortcomings, and activity enhancement strategies including the design of nanostructures, elemental doping, and heterojunctions construction such as Type-I, Type-II, Z-Type, and uncommon heterojunctions. Besides, the optical and electronic properties, charge carriers separation, electron transport phenomenon and alignment of the band gaps in LaFeO3-based heterostructures are comprehensively discussed.

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Cu3P nanoparticles confined in nitrogen/phosphorus dual-doped porous carbon nanosheets for efficient potassium storage Yuanxing Yun, Baojuan Xi, Yu Gu, Fang Tian, Weihua Chen, Jinkui Feng, Yitai Qian, Shenglin Xiong 2022, 66(3): 339-347.  DOI: 10.1016/j.jechem.2021.05.045 Abstract ( 5 )   PDF (7319KB) ( 2 )   Immobilizing primary electroactive nanomaterials in porous carbon matrix is an effective approach for boosting the electrochemical performance of potassium-ion batteries (PIBs) because of the synergy among functional components. Herein, an integrated hybrid architecture composed of ultrathin Cu3P nanoparticles (~20 nm) confined in porous carbon nanosheets (Cu3P⊂NPCSs) as a new anode material for PIBs is synthesized through a rational self-designed self-templating strategy. Benefiting from the unique structural advantages including more active heterointerfacial sites, intimate and stable electrical contact, effectively relieved volume change, and rapid K+ ion migration, the Cu3P⊂NPCSs indicate excellent potassium-storage performance involving high reversible capacity, exceptional rate capability, and cycling stability. Moreover, the strong adsorption of K+ ions and fast potassium-ion reaction kinetics in Cu3P⊂NPCSs is verified by the theoretical calculation investigation. Noted, the intercalation mechanism of Cu3P to store potassium ions is, for the first time, clearly confirmed during the electrochemical process by a series of advanced characterization techniques.

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In-situ growth of CoNi bimetal anchored on carbon nanoparticle/nanotube hybrid for boosting rechargeable Zn-air battery Jun Li, Yongxia Wang, Zhengyu Yin, Rui He, Yihao Wang, Jinli Qiao 2022, 66(3): 348-355.  DOI: 10.1016/j.jechem.2021.08.007 Abstract ( 9 )   PDF (7770KB) ( 2 )   Exploring highly efficient non-precious metal based catalysts for bifunctional oxygen electrode is crucial for rechargeable metal-air batteries. In this study, with MOFs as precursors, a facile coprecipitation method is designed to realize in-situ growth of the CoNi anchored carbon nanoparticle/nanotube (CoNi/N-CNN) hybrid, which can achieve the simultaneous maximum exposure of both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) active centers. Benefiting from the unique structure, the CoNi/N-CNN catalyst exhibits excellent electrocatalytic performance for ORR (Eonset = 1.183 V, E1/2 = 0.819 V) and a low operating voltage of 1.718 V at 10 mA cm-2 (Ej=10) for OER. Delightfully, the home-made rechargeable Zn-air battery with CoNi/N-CNN delivers a high discharge power density up to 209 mW cm-2, and an outstanding charge-discharge cycling stability. The boosted bifunctional electrocatalytic activity can be ascribed to the strong coupling effect between Co/Ni center sites and defect-rich N-anchored carbon featured with porous and nanotube structure, which can introduce uniformly dispersed active sites, tailored electronic configuration, superb conductivity and convenient charge transfer process. The hybrid non-precious bimetal based electrocatalyst provides the possibility to develop the low-cost and high-efficient ORR/OER bifunctional electrocatalysts in rechargeable metal-air battery.

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Metallic phase W0.9Mo0.1S2 for high-performance anode of sodium ion batteries through suppressing the dissolution of polysulfides Huachao Tao, Jing Li, Jinhang Li, Zhenhua Hou, Xuelin Yang, Li-Zhen Fan 2022, 66(3): 356-365.  DOI: 10.1016/j.jechem.2021.08.026 Abstract ( 9 )   PDF (14648KB) ( 3 )   WS2 with layered graphite-like structure as anode for sodium ion batteries has high specific capacity. However, the poor cycling performance and rate capability of WS2 caused by the low electronic conductivity and structure changes during cycles inhibit its practical application. Herein, metallic phase (1T) WxMo1-xS2 (x = 1, 0.9, 0.8 and 0.6) with high electronic conductivity and expanded interlayer spacing of 0.95 nm was directly prepared via a simple hydrothermal method. Specially, 1T W0.9Mo0.1S2 as anode for sodium ion batteries displays high capacities of 411 mAh g-1 at 0.1 A g-1 after 180 cycles and 262 mAh g-1 at 1 A g-1 after 280 cycles and excellent rate capability (245 mAh g-1 at 5 A g-1). The full cell based on Na3V2(PO4)2O2F/C cathode and 1T W0.9Mo0.1S2 anode also exhibits high capacity and good cycling performance. The irreversible electrochemical reaction of 1T W0.9Mo0.1S2 with Na ions during first few cycles results in the main products of W-Mo alloy and S. The strong adsorption of W-Mo alloy with polysulfides can effectively suppress the dissolution and shuttle effect of polysulfides, which ensures the excellent cycling performance of 1T W0.9Mo0.1S2.

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Dendrite-free lithium anode achieved under lean-electrolyte condition through the modification of separators with F-functionalized Ti3C2 nanosheets Qiang Zhang, Xiao Wei, Yu-Si Liu, Xin Liu, Wen-Long Bai, Zhen Zhang, Kai-Xue Wang, Jie-Sheng Chen 2022, 66(3): 366-373.  DOI: 10.1016/j.jechem.2021.08.013 Abstract ( 6 )   PDF (5285KB) ( 3 )   An unstable solid electrolyte interphase (SEI) and chaotic lithium ion flux are key impediments to commercial high-energy-density lithium batteries because of the uncontrolled growth of rigid lithium dendrites, which would pierce through the conventional polypropylene (PP) separator, causing short circuit and safety issues. Herein, the homogenization of lithium ion flux and the generation of stable SEI layers on lithium anodes were achieved via coating a fluorine-functionalized Ti3C2 (F-Ti3C2) nanosheets on PP separator (F-Ti3C2@PP). F-Ti3C2 nanosheets provide abundant ions pathways to homogeneously manipulate lithium ion flux and increase the Young's modulus and electrolyte wettability of the separators. In addition, F species derived from the F-Ti3C2 nanosheets would promote the formation of LiF-rich SEI film. The synergistic effect contribute to the uniform lithium deposition. Symmetric Li|Li, asymmetric Li|Cu and full Li|LiFePO4 cells incorporated with the modified separators exhibit improved electrochemical performance even under lean electrolyte conditions. This work provides a feasible strategy to improve the performance of lithium batteries through both fluoridized SEI formation and lithium ion flux manipulation.

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Manipulating the morphology of CdS/Sb2S3 heterojunction using a Mg-doped tin oxide buffer layer for highly efficient solar cells Jiashuai Li, Liangbin Xiong, Xuzhi Hu, Jiwei Liang, Feihong Ye, Jing Li, Yongjie Liu, Wenlong Shao, Ti Wang, Chen Tao, Guojia Fang 2022, 66(3): 374-381.  DOI: 10.1016/j.jechem.2021.08.029 Abstract ( 5 )   PDF (2804KB) ( 2 )   Antimony sulfide (Sb2S3) is an appealing semiconductor as light absorber for solar cells due to its high absorption coefficient, appropriate band gap (~1.7 eV) and abundance of constituent elements. However, power conversion efficiency (PCE) of Sb2S3-based solar cells still lags much behind the theoretically predicted due to the imperfect energy level alignment at the charge transporting layer/Sb2S3 interfaces and hence severe charge recombination. Herein, we insert a high-temperature sintered magnesium (Mg)-doped tin oxide (SnO2) layer between cadmium sulfide (CdS) and fluorine doped tin oxide to form a cascaded energy level alignment and thus mitigate interfacial charge recombination. Simultaneously, the inserted Mg-doped SnO2 buffer layer facilitates the growth of the neibouring CdS film with orientation followed by Sb2S3 film with larger grains and fewer pinholes. Consequently, the resultant Sb2S3 solar cells with Mg-doped SnO2 deliver a champion PCE of 6.31%, 22.8% higher than those without a buffer layer. Our work demonstrates that deliberate absorber growth as well as efficient hole blocking upon an appropriate buffer layer is viable in obtaining solution-processed Sb2S3 solar cells with high performance.

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N-alkyl chain modification in dithienobenzotriazole unit enabled efficient polymer donor for high-performance non-fullerene solar cells Jiaxin Xu, Hexiang Feng, Yuanying Liang, Haoran Tang, Yixu Tang, Zurong Du, Zhicheng Hu, Fei Huang, Yong Cao 2022, 66(3): 382-389.  DOI: 10.1016/j.jechem.2021.08.033 Abstract ( 10 )   PDF (6811KB) ( 2 )   Molecular design of either polymer donors or acceptors is a promising strategy to tune the morphology of the active layer of organic solar cells, enabling a high-performance device. Thereinto, developing novel polymer donors is an alternative method to obtain high photovoltaic performance. Herein, we present a facile side-chain engineering on the dithiophenobenzotriazole (DTBTz) unit of newly-designed polymer donors (named pBDT-DTBTz-EH and pBDT-DTBTz-Me) to boost the performance of non-fullerene solar cells. Compared with pBDT-DTBTz-EH with long N-alkyl side chains, pBDT-DTBTz-Me with a short methyl exhibits stronger molecular aggregation, higher absorption coefficient, and preferred face-on orientation packing. As a consequence, pBDT-DTBTz-Me based devices achieve an optimal power conversion efficiency of 15.31% when donors are paired with the narrow bandgap acceptor Y6, which is superior to that of pBDT-DTBTz-EH based devices (9.17%). Additionally, the pBDT-DTBTz-Me based devices manifest more effective charge separation and transfer than pBDT-DTBTz-EH based devices. These results indicate that fine-tuning side chains of polymer donors provide new insights for the design of high-performance polymer donors in non-fullerene solar cells.

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Self-discharge mitigation in a liquid metal displacement battery Kashif Mushtaq, Ji Zhao, Norbert Weber, Adelio Mendes, Donald R. Sadoway 2022, 66(3): 390-396.  DOI: 10.1016/j.jechem.2021.08.015 Abstract ( 7 )   PDF (3563KB) ( 2 )   Recently, a disruptive idea was reported about the discovery of a new type of battery named Liquid Displacement Battery (LDB) comprising liquid metal electrodes and molten salt electrolyte. This cell featured a novel concept of a porous electronically conductive faradaic membrane instead of the traditional ion-selective ceramic membrane. LDBs are attractive for stationary storage applications but need mitigation against self-discharge. In the instant battery chemistry, Li|LiCl-PbCl2|Pb, reducing the diffusion coefficient of lead ions can be a way forward and a solution can be the addition of PbO to the electrolyte. The latter acts as a supplementary barrier and complements the function of the faradaic membrane. The remedial actions improved the cell's coulombic efficiency from 92% to 97% without affecting the voltage efficiency. In addition, the limiting current density of a 500 mAh cell increased from 575 to 831 mA cm-2 and the limiting power from 2.53 to 3.66 W. Finally, the effect of PbO on the impedance and polarization of the cell was also studied.

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Different surface modification methods and coating materials of zinc metal anode Feng Tao, Yong Liu, Xinyuan Ren, Jing Wang, Yazhou Zhou, Yingjie Miao, Fengzhang Ren, Shizhong Wei, Jianmin Ma 2022, 66(3): 397-412.  DOI: 10.1016/j.jechem.2021.08.022 Abstract ( 11 )   PDF (18089KB) ( 5 )   Rechargeable aqueous Zn-ion batteries (AZIBs) are one of the most promising energy storage devices for large-scale energy storage owing to their high specific capacity, eco-friendliness, low cost and high safety. Nevertheless, zinc metal anodes suffer from severe dendrite growth and side reactions, resulting in the inferior electrochemical performance of AZIBs. To address these problems, surface modification of zinc metal anodes is a facile and effective method to regulate the interaction between the zinc anode and an electrolyte. In this review, the current challenges and strategies for zinc metal anodes are presented. Furthermore, recent advances in surface modification strategies to improve their electrochemical performance are concluded and discussed. Finally, challenges and prospects for future development of zinc metal anodes are proposed. We hope this review will be useful for designing and fabricating high-performance AZIBs and boosting their practical applications.

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Sn4P3 nanoparticles confined in multilayer graphene sheets as a high-performance anode material for potassium-ion batteries Yichen Du, Zuyue Yi, Bingbing Chen, Jingyi Xu, Zhuangzhuang Zhang, Jianchun Bao, Xiaosi Zhou 2022, 66(3): 413-421.  DOI: 10.1016/j.jechem.2021.08.043 Abstract ( 6 )   PDF (6661KB) ( 2 )   Phosphorus-based anodes are highly promising for potassium-ion batteries (PIBs) because of their large theoretical capacities. Nevertheless, the inferior potassium storage properties caused by the poor electronic conductivity, easy self-aggregation, and huge volumetric changes upon cycling process restrain their practical applications. Now we impregnate Sn4P3 nanoparticles within multilayer graphene sheets (Sn4P3/MGS) as the anode material for PIBs, greatly improving its potassium storage performance. Specifically, the graphene sheets can efficiently suppress the aggregation of Sn4P3 nanoparticles, enhance the electronic conductivity, and sustain the structural integrity. In addition, plenty of Sn4P3 nanoparticles impregnated in MGS offer a large accessible area for the electrolyte, which decreases the diffusion distance for K+ and electrons upon K+ insertion/extraction, resulting in an improved rate capability. Consequently, the optimized Sn4P3/MGS containing 80 wt% Sn4P3 (Sn4P3/MGS-80) exhibits a high reversible capacity of 378.2 and 260.2 mAh g-1 at 0.1 and 1 A g-1, respectively, and still delivers a large capacity retention of 76.6% after the 1000th cycle at 0.5 A g-1.

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Facile lattice tensile strain compensation in mixed-cation halide perovskite solar cells Shurong Wang, Jie Hu, Aili Wang, Yuying Cui, Bin Chen, Xiaobin Niu, Feng Hao 2022, 66(3): 422-428.  DOI: 10.1016/j.jechem.2021.08.044 Abstract ( 7 )   PDF (5313KB) ( 3 )   Despite the rapid development of power conversion efficiency (PCE) for halide perovskite solar cells (PSCs), the lattice strain engineering in perovskite thin films has been rarely probed in recent years. Herein, a strain compensation by homogeneous crystallization in perovskite films is achieved with the aid of precursor aging in the mixed-cation perovskite of Cs0.05(FA0.83MA0.17)Pb(I0.90Br0.10)3 with near 20% PCE in inverted devices. The homogeneous crystallization releases the residual tensile stress and induces more compressive stress at the edges of perovskite films, thus elongating the carrier lifetime and reducing the trap-assisted carrier recombination. The high dependence on the perovskite components in strain engineering strategy was systematically revealed, wherein MAPbI3 and Cs0.05(FA0.83MA0.17)PbI3 film showed an increased compressive strain and FAPbI3 film showed adverse tensile strain after aging. The density functional theory (DFT) calculations are further performed to reveal the change of electronic features. The precursor aging-induced strain modulation was correlated with a systematic characterization of the charge carrier transport and recombination dynamics in the mixed-cation perovskite films. We believe that this facile approach provides a novel strain engineering strategy for PSCs technology.

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3D MXene architectures as sulfur hosts for high-performance lithium-sulfur batteries Yu-Hong Liu, Cao-Yu Wang, Si-Lin Yang, Fei-Fei Cao, Huan Ye 2022, 66(3): 429-439.  DOI: 10.1016/j.jechem.2021.08.040 Abstract ( 5 )   PDF (10674KB) ( 1 )   Lithium-sulfur batteries (LSBs) are one of the most promising energy storage devices because of their high theoretical energy density; however, inherent issues including poor electrical conductivity and severe dissolution of S and its discharged products hinder their practical applications. MXenes have metallic conductivity, ultra-thin two-dimensional (2D) structures, rich surface functional groups, and macrostructural adjustability and have been widely used to design advanced sulfur hosts. 3D network structures assembled by 2D MXene nanosheets have shown superior performance for improving reaction kinetics, accommodating and dispersing sulfur at the micro-/nanoscale, and capturing polysulfides due to their porous interconnected structure. Herein, the applications of MXene architectures related to 2D layered structures, 3D multilayered structures, and 3D spherical structures as sulfur hosts are reviewed. The structure-performance relationship, challenges for current designs, and opportunities for future 3D architectures for LSBs are also analyzed.

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A model cathode for mechanistic study of organosulfide electrochemistry in Li-organosulfide batteries WeiZhang, FenfenMa, SibeiGuo, XinChen, ZiqiZeng, QiangWu, ShupingLi, ShijieCheng, JiaXie 2022, 66(3): 440-447.  DOI: 10.1016/j.jechem.2021.08.045 Abstract ( 4 )   PDF (6826KB) ( 2 )   Organosulfides offer new opportunities for high performance lithium-sulfur (Li-S) batteries because of materials abundance, versatile structures and unique properties. Yet, their redox kinetics as well as cycling performance need to be further improved. Employing redox mediators is a highly effective strategy to address above challenges. However, the underlying mechanism in this chemistry is so far insufficiently explored. Here, phenyl disulfide (PhS-SPh) and phenyl diselenide (PhSe-SePh) are used as a model system for mechanistic understanding of organosulfide electrochemistry, particularly the rate acceleration. Profiling the reaction thermodynamics and charge-discharge process reveals redox of both S-S and C-S bonds, as well as that the coupling between radical exchange and electrochemical redox is the key to enhance the sulfur kinetics. This study not only establishes a basic understanding of orgaonsulfide electrochemistry in Li-S batteries, but also points out a general strategy for enhancing the kinetics of sulfur electrodes in electrochemical devices.

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Insights into the thermochemical evolution of maleic anhydride-initiated esterified starch to construct hard carbon microspheres for lithium-ion batteries Ming-Xin Song, Li-Jing Xie, Jia-Yao, Cheng, Zong-Lin Yi, Ge Song, Xiao-Yang Jia, Jing-Peng Chen, Quan-Gui Guo, Cheng-Meng Chen 2022, 66(3): 448-458.  DOI: 10.1016/j.jechem.2021.08.050 Abstract ( 28 )   PDF (8983KB) ( 23 )   Starch, as a typical polysaccharide with natural spherical morphology, is not only a preferred precursor for preparing carbon materials but also a model polymer for investigating thermochemical evolution mechanisms. However, starch usually suffers from severe foaming and low carbon yield during direct pyrolysis. Herein, we report a simple and eco-friendly dry strategy, by maleic anhydride initiating the esterification of starch, to design carbon microspheres against the starch foaming. Moreover, the influence of ester grafting on the pyrolytic behavior of starch is also focused. The formation of ester groups in precursor guarantees the structural stability of starch-based intermediate because it can promote the accumulation of unsaturated species and accelerate the water elimination during pyrolysis. Meanwhile, the esterification and dehydration reactions greatly deplete the primary hydroxyl groups in the starch molecules and thus the rapid levoglucosan release is inhibited, which well keeps the spherical morphology of starch and ensures the high carbon yield. In further exploration as anode materials for Lithium-ion batteries, the obtained carbon microspheres exhibit good cyclability and rate performance with a reversible capacity of 444 mAh g-1 at 50 mA g-1. This work provides theoretical fundamentals for the controllable thermal transformation of biomass towards wide applications.

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Effect of dimensional expansion on carrier transport behaviors of the hexagonal Bi-based perovskite crystals Qihao Sun, Bao Xiao, Leilei Ji, Dou Zhao, Jinjin Liu, Wei Zhang, Menghua Zhu, Wanqi Jie, Bin-Bin Zhang, Yadong Xu 2022, 66(3): 459-465.  DOI: 10.1016/j.jechem.2021.08.052 Abstract ( 3 )   PDF (7137KB) ( 2 )   All-inorganic Cs3Bi2I9 (CBI) halide perovskites are sought to be candidate for photoelectrical materials because of their low toxicity and satisfactory stability. Unfortunately, the discrete molecular [Bi2I9]3- clusters limit the charge-transport behaviors. Herein, the defect halide perovskite based on trivalent Bi3+ is expanded to Cs3Bi2I6Br3 (CBIB). Centimeter-size CBIB single crystal (Φ 15 × 70 mm3) was grown by the vertical Bridgeman method. The powder X-ray diffraction analysis shows that CBIB has P3-m1 structure with lattice parameters of a = b = 8.223 Å, c = 10.024 Å, α = β = 90° and γ = 120°. The density functional theory (DFT) calculations demonstrate that the charge density distribution was enhanced after the dimensional expansion. The enhancement of carrier transport ability of (00l) in-plane is characterized before and after dimensional improvement. The obtained CBIB(001) exhibited an electron mobility up to 40.03 cm2 V-1 s-1 by time-of-flight (TOF) technique, higher than 26.46 cm2 V-1 s-1 of CBI(001). Furthermore, the X-ray sensitivity increases from 707.81 μC Gy-1 cm-2 for CBI(001) to 3194.59 μC Gy-1 cm-2 for CBIB(001). This research will deepen our understanding of Bi-based perovskite materials and afford more promising strategies for lead-free perovskite optoelectronic devices modification.

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Enhanced bifunctional catalytic activities of N-doped graphene by Ni in a 3D trimodal nanoporous nanotubular network and its ultralong cycling performance in Zn-air batteries Yanyi Zhang, Xiang-Peng Kong, Xiaorong Lin, Kailong Hu, Weiwei Zhao, Guoqiang Xie, Xi Lin, Xingjun Liu, Yoshikazu Ito, Hua-Jun Qiu 2022, 66(3): 466-473.  DOI: 10.1016/j.jechem.2021.08.054 Abstract ( 5 )   PDF (7751KB) ( 4 )   Free-standing and flexible air electrodes with long-lasting bifunctional activities for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are crucial to the development of wearable Zn-air rechargeable batteries. In this work, we synthesize a flexible air electrode consisting of 3D nanoporous N-doped graphene with trimodal shells and Ni particles through repeated chemical vapor deposition (CVD) and acidic etching processes. Our results indicate that such trimodal graphene morphology significantly enhances the active N-dopant sites and graphene-coated Ni surface, which consequentially boosts both the ORR and OER activities, as well as catalytic durability. First-principles density functional theory (DFT) calculations reveal the synergetic effects between the Ni and the N-doped graphene; namely, the Ni nanoparticles boost the bifunctional activities of the coated N-doped graphene, and in turn the graphene-covering layers enhance the stability of Ni. Thanks to the better protection from the triple graphene shells, our trimodal N-doped graphene/Ni-based Zn-air battery can be stably discharged/recharged beyond 2500 h with low overpotentials. It is reasonable to expect that such free-standing trimodal graphene/Ni would be promising in many flexible energy conversion/storage devices.

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Direct insight into sulfiphilicity-lithiophilicity design of bifunctional heteroatom-doped graphene mediator toward durable Li-S batteries Haina Ci, Menglei Wang, Zhongti Sun, Chaohui Wei, Jingsheng Cai, Chen Lu, Guang Cui, Zhongfan Liu, Jingyu Sun 2022, 66(3): 474-482.  DOI: 10.1016/j.jechem.2021.08.048 Abstract ( 6 )   PDF (8800KB) ( 2 )   The practical applications of lithium-sulfur (Li-S) battery have been greatly hindered by the severe polysulfide shuttle at the cathode and rampant lithium dendrite growth at the anode. One of the effective solutions deals with concurrent management of both electrodes. Nevertheless, this direction remains in a nascent stage due to a lack of material selection and mechanism exploration. Herein, we devise a temperature-mediated direct chemical vapor deposition strategy to realize the controllable synthesis of three-dimensional boron/nitrogen dual-doped graphene (BNG) particulated architectures, which is employed as a light-weighted and multi-functional mediator for both electrodes in Li-S batteries. Benefiting from the “sulfiphilic” and “lithiophilic” features, the BNG modified separator not only enables boosted kinetics of polysulfide transformation to mitigate the shuttle effect but also endows uniform lithium deposition to suppress the dendritic growth. Theoretical calculations in combination with electro-kinetic tests and operando Raman analysis further elucidate the favorable sulfur and lithium electrochemistry of BNG at a molecular level. This work offers direct insight into the mediator design via controllable synthesis of graphene materials to tackle the fundamental challenges of Li-S batteries.

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High valence state of Ni and Mo synergism in NiS2-MoS2 hetero-nanorods catalyst with layered surface structure for urea electrocatalysis Shuli Wang, Linyu Zhao, Jiaxin Li, Xinlong Tian, Xiang Wu, Ligang Feng 2022, 66(3): 483-492.  DOI: 10.1016/j.jechem.2021.08.042 Abstract ( 5 )   PDF (12125KB) ( 4 )   High valence state species are significant in the energy-relevant electrochemical oxidation reactions. Herein, the high active state of Ni3+ formation induced by Mo6+ and their efficient synergism in NiS2-MoS2 hetero-nanorods powder catalyst with the rough layered structure are demonstrated, as proof of concept, for the urea-assisted water electrolysis. This catalyst can be derived from the sulfidation of NiMoO4 nanorods that can realize individual metal sulfides sufficiently mixing at a domain size in the nanoscale which creates lots of active sites and nanointerfaces. The high valence state of Mo6+ and Ni3+ formation and increased conductive phase of 1 T MoS2 in the hetero-nanorods compared to the counterpart pure phases are revealed by spectral study and microscopic analysis; high electrochemical surface area and active site exposure are found due to the nano-interface formation and layered rough nanosheets over the surface of nanorods. They show much higher catalytic performance than their pure phases for urea oxidation, including high catalytic activity, stability, charge transfer ability and catalytic kinetics resulting from more active Ni3+ species formation and electronic synergism of high valence metals. Transformation of 1 T MoS2 to Mo6+ and increased amount of Mo6+ and Ni3+ after stability test indicate their involvement and synergism for the catalysis reaction. The current work offers a novel understanding of the synergistic effect based on the high valence state synergism for heterogeneous catalysts in electrocatalysis.

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One stone two birds: Vanadium doping as dual roles in self-reduced Ptclusters and accelerated water splitting Yihan Feng, Zichuang Li, Shanlin Li, Minghui Yang, Ruguang Ma, Jiacheng Wang 2022, 66(3): 493-501.  DOI: 10.1016/j.jechem.2021.08.061 Abstract ( 4 )   PDF (5382KB) ( 2 )   Integrating active Pt clusters into transition-metal oxides with water-dissociation ability is effective to prepare a bifunctional electrocatalyst for water splitting in alkaline. However, the additional utilization of a reductant and/or the operation at the elevating temperature causes the over-growth and agglomeration of Pt clusters, thus losing the high catalytic performance. Herein, we report that V dopant not only favors self-reducing Pt clusters on NiFe layered double hydroxide (LDH) (Pt/NiFeV) at room temperature, but also regulates interfacial charge redistribution to enhance the water-splitting performance. Experimental and theoretical studies reveal that V dopant into NiFe LDH triggers more electrons to transfer to adjacent Fe atoms, thus leading to a higher reducing ability compared to that without V-doping. When used as water-splitting electrocatalyst, V doping promotes electron loss of Pt clusters in Pt/NiFeV, optimizing the free energy of hydrogen adsorption and proton recombination kinetics at the cathode. Meanwhile, it also moves the d-band center of Ni away from the Fermi level to optimize the adsorption of *OH intermediates and facilitate the desorption of oxygen molecules at the anode. Thereby, Pt/NiFeV exhibits much higher bifunctional performance than V-free Pt/NiFe LDH toward both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This work can spark inspiration of designing other bifunctional electrocatalysts for energy conversion and storage.

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Interface-directed epitaxially growing nickle ensembles as efficient catalysts in dry reforming of methane Ping Wang, Song Wei, Shiyi Wang, Ronghe Lin, Xiaoling Mou, Yunjie Ding 2022, 66(3): 502-513.  DOI: 10.1016/j.jechem.2021.08.065 Abstract ( 9 )   PDF (15917KB) ( 3 )   Supported nickel catalysts are promising candidates for dry reforming of methane, but agglomeration of Ni0 and coke deposition hinder the industrial applications. Herein, we report a novel interface-directed synthetic approach to construct distinct metal ensembles by carefully tuning the compositions of the carriers. A Zr-Mn-Zn ternary oxide-supported Ni catalyst, together with the respective binary oxide-supported analogues, was synthesized by adopting a sequential co-precipitation and wetness impregnation method. Combined characterization techniques identify distinct catalyst models, including (i) conventional NiO nanoparticles with different sizes on Zr-Mn and Zr-Zn, and (ii) epitaxially growing NiO ensembles of a few nanometers thickness at the periphery of MnZnOx particles. These catalysts exhibit divergent responses in the catalytic testing, with the ternary oxide system significantly outperforming the binary analogues. The strong electronic interactions between Mn-Ni increase Ni dispersion and the activity while the stability is strengthened upon Zn addition. Both high activity, high selectivity, and remarkable stability are attained upon co-adding Mn and Zn. The interfaces between Ni and Zr-Mn-Zn rather than the physical contacts of individual oxide-supported analogues through mechanical mixing are keys for the outstanding performance.

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Boron modulating electronic structure of FeN4C to initiate high-efficiency oxygen reduction reaction and high-performance zinc-air battery Xue Zhao, Xue Li, Zenghui Bi, Yuwen Wang, Haibo Zhang, Xiaohai Zhou, Quan Wang, Yingtang Zhou, Huaisheng Wang, Guangzhi Hu 2022, 66(3): 514-524.  DOI: 10.1016/j.jechem.2021.08.067 Abstract ( 8 )   PDF (6145KB) ( 4 )   The biggest challenge is to develop a low cost and readily available catalyst to replace expensive commercial Pt/C for efficient electrochemical oxygen reduction reaction (ORR). In this research, closo-[B12H12]2- and 1,10-phenanthroline-iron complexes were introduced into the porous metal-organic framework by impregnation method, and further annealing treatment achieved the successful anchoring of single-atom-Fe in B-doped CN Matrix (FeN4CB). The ORR activity of FeN4CB is comparable to the widely used commercial 20 wt% Pt/C. Where the half-wave potential (E1/2) in alkaline medium up to 0.84 V, and even in the face of challenging ORR in acidic medium, the E1/2 of ORR driven by FeN4CB is still as high as 0.81 V. When FeN4CB was used as air cathode, the open circuit voltage of Zn-air battery reaches 1.435 V, and the power density and specific capacity are as high as 177 mW cm-2 and 800 mAh gZn-1 (theoretical value: 820 mAh gZn-1), respectively. The dazzling point of FeN4CB also appears in the high ORR stability, whether in alkaline or acidic media, E1/2 and limiting current density are still close to the initial value after 5000 times cycles. After continuously running the charge-discharge test for 220 h, the charge voltage and discharge voltage of the rechargeable zinc-air battery with FeN4CB as the air cathode maintained the initial state. Density functional theory calculations reveals that introducing B atom to Fe-N4-C can adjust the electronic structure to easily break O = O bond and significantly reduce the energy barrier of the rate-determining step resulting in an improved ORR activity.

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Intermarriage between amorphous and polycrystalline materials in perovskite solar cells: positive or not? Ying Tan, Xueqing Chang, Bing-Xin Lei, Wu-Qiang Wu 2022, 66(3): 525-528.  DOI: 10.1016/j.jechem.2021.08.063 Abstract ( 10 )   PDF (2378KB) ( 5 )

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Recent advances in non-metal doped titania for solar-driven photocatalytic/photoelectrochemical water-splitting Ying-Ying Wang, Yan-Xin Chen, Tarek Barakat, Yu-Jia Zeng, Jing Liu, Stéphane Siffert, Bao-Lian Su 2022, 66(3): 529-559.  DOI: 10.1016/j.jechem.2021.08.038 Abstract ( 30 )   PDF (15175KB) ( 26 )   Photocatalytic (PC) / Photoelectrochemical (PEC) water splitting under solar light irradiation is considered as a prospective technique to support the sustainable and renewable H2 economy and to reach the ultime goal of carbon neutral. TiO2 based photocatalysts with high chemical stability and excellent photocatalytic properties have great potential for solar-to-H2 conversion. To conquer the challenges of the large band-gap and rapid recombination of photo generated electron-holepairs in TiO2, non-metal doping turns out to be economic, facile, and effective on boosting the visible light activity. The localized defect states such as oxygen vacancy and Ti3+ generated by non-metal doping are located in the band-gap of TiO2, which result in the reduction of band-gap, thus a red-shift of the absorption edge. The hetero doping atoms such as B3+, I7+, S4+/S6+, P5+ can also act as electron donors or trap sites which facilitate the charge carrier separation and suppress the recombination of electron-hole pairs. In this comprehensive review, we present the most recent advances on non-metal doped TiO2 photocatalysts in terms of fundamental aspects, origin of visible light activity and the PC / PEC behaviours for water splitting. In particular, the characteristics of different non-metal elements (N, C, B, S, P, Halogens) as dopants are discussed in details focusing on the synthesis approaches, characterization as well as the efficiency of PC and PEC water splitting. The present review aims at guiding the readers who want quick access to helpful information about how to efficiently improve the performance of photocatalysts by simple doping strategies and could stimulate new intuitive into the new doping strategies.

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Pollen-like self-supported FeIr alloy for improved hydrogen evolution reaction in acid electrolyte Shengyu Ma, Jun Deng, Yaping Xu, Weiying Tao, Xiaoqi Wang, Zhiping Lin, Qinghua Zhang, Lin Gu, Wenwu Zhong 2022, 66(3): 560-565.  DOI: 10.1016/j.jechem.2021.08.066 Abstract ( 3 )   PDF (5614KB) ( 2 )   Ir is recognized as efficient catalyst for hydrogen evolution reaction (HER). The high price, however, has hindered its application in the production of hydrogen. In this work, we prepared the self-supported FeIr alloy nanoparticles, taking advantage of solid-state synthesis method. The as-prepared FeIr alloy possesses a novel morphology of pollen, which is consist of smaller FeIr nanoparticles. DFT calculations reveal that the change of the free Gibbs for Ir is negative after the adsorption of active H, while it is positive for the case of Fe. Thus, the alloying of Fe and Ir not only effectively reduces the cost, but also can achieve more adequate adsorption of active H species. Benefitting from this, the as-prepared FeIr alloy nanoparticle exhibits superior HER performance with an overpotential of 19 mV at a current density of 10 mV/cm2 and a Tafel slope of 32 mV/dec, when tested in 0.5 M H2SO4, better than pure Ir and Pt/C. This work paves the way to the exploration of efficient alloy electrocatalysts for HER.

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Surface functionalized Pt/SnNb2O6 nanosheets for visible-light-driven the precise hydrogenation of furfural to furfuryl alcohol Yingzhang Shi, Huan Wang, Zhiwen Wang, Cheng Liu, Mingchuang Shen, Taikang Wu, Ling Wu 2022, 66(3): 566-575.  DOI: 10.1016/j.jechem.2021.09.003 Abstract ( 3 )   PDF (10845KB) ( 1 )   Photocatalytic upgrading of renewable biomass is a promising way to relieve energy crisis and environmental pollution. However, low photocatalytic efficiency and uncontrollable selectivity still limit its development. Herein, ultrathin SnNb2O6 nanosheets with high dispersed Pt nanoparticles (Pt/SN) were successfully developed as an efficient photocatalyst for the precise hydrogenation of furfural (FUR) to furfuryl alcohol (FOL) under visible light irradiation and exhibited the high conversion of FUR (99.9%) with the high selectivity for FOL (99.9%). It was revealed that SN with only 4.1 nm thickness possess good separation ability of photo-generated carriers and abundant surface Lewis acid sites (Nb5+) which would selectively chemisorb and activate FUR molecules via the Nb···O = C coordination. Meanwhile, Pt nanoparticles would gather photo-generated electrons for greatly promoting the generation of active H species to support the hydrogenation of FUR to FOL. The synergistic effects between SnNb2O6 nanosheets and Pt nanoparticles remarkably facilitate the photocatalytic performance for hydrogenation. This work not only confirms the great potential of ultrathin nanosheet photocatalyst with functional metal sites for precise upgrading of biomass but also provides an in-depth view to understand the surface/interface interaction between reactant molecules and surface sites of a photocatalyst.

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Regulating the nanoscale intimacy of metal and acidic sites in Ru/γ-Al2O3 for the selective conversions of lignin-derived phenols to jet fuels Shanshuai Chen, Weichen Wang, Xue Li, Puxiang Yan, Wanying Han, Tian Sheng, Tiansheng Deng, Wanbin Zhu, Hongliang Wang 2022, 66(3): 576-586.  DOI: 10.1016/j.jechem.2021.08.058 Abstract ( 7 )   PDF (10649KB) ( 1 )   Catalytic hydrodeoxygenation (HDO) of biomass-derived oxy-compounds to advanced hydrocarbon fuels usually requires bifunctional catalysts containing metals and acidic sites. The appropriate tuning of metal and/or acidic active sites at interfaces of bifunctional catalysts can significantly improve catalyst activity and product selectivity. Here, 4-trifuoromethyl salicylic acid (TFMSA), as a hydrothermal stable organic acid, was employed to tailor the bifunctional interface of Ru/γ-Al2O3 to enhance the catalytic performance on converting lignin-derived phenols to jet fuel range cycloalkanes. More than 80% phenol was converted into cyclohexane at 230 °C for 1 h over Ru/γ-Al2O3 modified by TFMSA, which was about three times higher than that over unmodified Ru/γ-Al2O3. X-ray diffraction (XRD), Transmission electron microscope (TEM), H2 chemisorption, and energy dispersive X-ray spectroscopy (EDS) elemental mapping results indicated that Ru nanoparticles and TFMSA were well distributed on γ-Al2O3, and a nanoscale intimacy between Ru and TFMSA was reached. Meanwhile, Fourier transform infrared spectroscopy after pyridine adsorption (Py-FT-IR) analysis proved that Brønsted acidic sites on the catalytic interfaces of TFMSA modified Ru/γ-Al2O3 had been improved. Moreover, the kinetic and density functional theory (DFT) results suggested that the synergistic effects of adjacent Ru nanoparticles and acidic sites were crutial for promoting the rate-limiting conversion step of phenol HDO to cyclohexane.

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Sulfurized-polyacrylonitrile in lithium-sulfur batteries: Interactions between undercoordinated carbons and polymer structure under low lithiation Samuel Bertolini, Timo Jacob 2022, 66(3): 587-596.  DOI: 10.1016/j.jechem.2021.08.070 Abstract ( 8 )   PDF (9913KB) ( 3 )   Lithium-sulfur battery (LSB) represents an important candidate to be used in energy storage applications, due to its high specific capacities. Sulfurized-polyacrylonitrile (SPAN) is a candidate as a host material in LSB to replace graphite, due to its ability to chemisorb polysulfides (PSs). The sulfur chains attached to the polymer can reversibly form Li2S, and SPAN indicates to have a good cyclability and better performance than graphite, thus, SPAN acts partially as an active and also as a host material. In this study, we investigated the capacity of the solvent or the SPAN to lose a hydrogen atom from the backbone, to predict possible anodic reactions between solvent and host material. The simulation suggests that the photophilic salts may preferentially react with the solvent, and possibly building a cathode electrolyte interphase (CEI). We observed that an undercoordinated carbon (Cuc) can be thermodynamically created, due to lithiation. The Cuc can react with the solvent on the polymer backbone through different mechanisms, however, the simulations indicated that the reaction should be affected by the interaction between the solvent and Cuc, according to SPAN's configuration. Moreover, Cuc reacts with long sulfur chains attached to SPAN, capturing sulfur and forming a C-S bond. A sulfur chain from one SPAN can connect to another polymer backbone, however, this process is affected by lithiation and vice-versa. Therefore, this work also investigates the formation of interconnected SPAN structures and the multiple Cuc effects.

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Achieving high conversion of syngas to aromatics Yi Fu, Youming Ni, Zhiyang Chen, Wenliang Zhu, Zhongmin Liu 2022, 66(3): 597-602.  DOI: 10.1016/j.jechem.2021.03.044 Abstract ( 5 )   PDF (4090KB) ( 2 )   Realizing high CO conversion and high aromatics selectivity simultaneously in syngas-to-aromatics (STA) reaction is still challenging. Herein, we report a 57.5% CO conversion along with 74% aromatics selectivity over a composite catalyst consisting of Fe/ZnCr2O4 (Fe modified ZnCr2O4 spinel) oxide and H-ZSM-5 zeolite. Impregnation of only 3 wt% of Fe onto ZnCr2O4 can remarkably increase CO conversion without sacrificing the aromatics selectivity. Oxygen vacancy concentration is improved after impregnating Fe. The highly dispersed iron carbide species is formed during the reaction over Fe/ZnCr2O4 spinel oxide. The synergistic effect of oxygen vacancy and iron carbide results in a rapid formation of abundant oxygenated intermediate species, which can be continuously transformed to aromatics in H-ZSM-5. This study provides a new insight into the design of highly efficient catalyst for syngas conversion.

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Rational design of CO2 electroreduction cathode via in situ electrochemical phase transition Shiqing Hu, Huan Li, Xue Dong, Zhongwei Cao, Bingjie Pang, Liming Zhang, Wenguang Yu, Jianping Xiao, Xuefeng Zhu, Weishen Yang 2022, 66(3): 603-611.  DOI: 10.1016/j.jechem.2021.08.069 Abstract ( 5 )   PDF (7192KB) ( 2 )   CO2 electroreduction reaction (CO2RR), combined with solid oxide electrolysis cells (SOECs), is a feasible technology for the storage of renewable electric energy, while its development is limited by the catalytic activity and stability on cathodes. Here, a novel garnet oxide (Gd3Fe5O12) cathode is designed, where the garnet oxide is converted to perovskite oxide and iron via in situ electrochemical phase transition during CO2 electroreduction, resulting in high activity with Faradaic efficiency close to 100% and great stability over 1000 h galvanostatic test. A variety of experimental characterizations and density functional theory calculations indicate that in situ exsolved Fe clusters can effectively enhance the adsorption energies of intermediates and lowering the CO2 dissociation barriers. Microkinetic modelling confirms that CO2RR goes through a dissociative adsorption mechanism and the electronic transfer for CO2 dissociation is the rate-determining step.

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Atmospheric stable and flexible Sn-based perovskite solar cells via a bio-inspired antioxidative crystal template Rui Guo, Li Rao, Qianjin Liu, Hongyu Wang, Chenxiang Gong, Baojin Fan, Zhi Xing, Xiangchuan Meng, Xiaotian Hu 2022, 66(3): 612-618.  DOI: 10.1016/j.jechem.2021.09.013 Abstract ( 6 )   PDF (3171KB) ( 2 )   Sn-based perovskite solar cells (PSCs) demonstrate a potential development in eco-friendly devices due to their hypotoxicity. However, poor stability and crystalline quality are still the challenges for achieving high-performance and long-term operating devices. In this work, inspired by biological protein, nickel-porphyrin (Ni-P) with electron cloud on conjugate ring is applied into Sn-based perovskite to prevent perovskite from being eroded. The synergistic effect of water and oxygen is broken in grain boundaries and surface so that the stability of PSCs can be improved obviously, despite there is hardly any barrier for water to erode. Simultaneously, the electron-rich molecules can passivate the defects of perovskite such as iodine vacancy. Moreover, the ester group in Ni-P molecule can bind with SnI2 to form complex and then restrain nucleation. Combining with the template effect of 2D molecular, the crystallization of perovskite films is optimized. Therefore, the Sn-based PSCs with Ni-P achieve a stabilized power conversion efficiency (PCE) of 7.79% with negligible hysteresis in flexible devices, respectively. Moreover, the PSCs can maintain 80% of the pristine PCE after 300 h under air environment.

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An ultrathin two-dimensional iridium-based perovskite oxide electrocatalyst with highly efficient {001} facets for acidic water oxidation Lan Yang, Kexin Zhang, Hui Chen, Lei Shi, Xiao Liang, Xiyang Wang, Yipu Liu, Qing Feng, Mingjie Liu, Xiaoxin Zou 2022, 66(3): 619-627.  DOI: 10.1016/j.jechem.2021.09.016 Abstract ( 19 )   PDF (9007KB) ( 7 )   The oxygen evolution reaction (OER) is an electrochemical bottleneck half-reaction in some important energy conversion systems (e.g., water splitting), which is traditionally mediated by iridium oxides in acidic environment. Perovskite-structured Ir-containing oxides (e.g., SrIrO3) are a family of striking electrocatalysts due to their high specific activity, but this excellent quality is difficultly transferred to a nano-electrocatalyst with large active surface and good structural stability. Here, we present a synthesis method that produces a 2D ultrathin {001}-faceted SrIrO3 perovskite (2D-SIO) with a thickness of ∼5 nm and high surface area (57.6 m2 g-1). We show that 2D-SIO can serve as a highly active and stable electrocatalytic nanomaterial for OER under acidic conditions. This perovskite nanomaterial produces 10 mA cm-2 current density at a low overpotential (η, 243 mV), and maintains its catalytic activity after 5000 continuous cyclic measurements. Besides ultrathin structure and large surface area, the exposed {001} facets are found to be the most crucial and unique structural factor for achieving high catalytic activity and structural stability. Our joint experimental and theoretical results demonstrate that these advantageous microstructural features of 2D-SIO endow it with a strong capability to generate the key O* intermediates, and thereby facilitate O-O bond formation and the OER.

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Achieving efficient N2 electrochemical reduction by stabilizing the N2H* intermediate with the frustrated Lewis pairs Zhe Chen, Jingxiang Zhao, Yan Jiao, Tao Wang, Lichang Yin 2022, 66(3): 628-634.  DOI: 10.1016/j.jechem.2021.09.020 Abstract ( 4 )   PDF (5914KB) ( 2 )   Electrocatalytic nitrogen reduction reaction (eNRR) with sustainable energy under ambient conditions represents an attractive approach to producing ammonia, but the design of the-state-of-the-art electrocatalyst with high efficiency and selectivity still faces formidable challenges. In contrast to traditional eNRR catalyst design strategies focusing on N≡N triple bond activation, we herein theoretically proposed an alternative strategy to improve eNRR performance via stabilizing the N2H* intermediate using catalysts with the frustrated Lewis pairs (FLPs), i.e., transition metal (TM) atoms and boron (B) atom co-doped 2D black phosphorus (TM-B@BP). Our density functional theory (DFT) results reveal that the TM atom donates electrons to the adsorbed N2 molecule, while B atom provides empty orbital to stabilize the adsorption of N2H* intermediate. This framework successfully identifies five promising candidates (i.e., Ti-B@BP, V-B@BP, Cr-B@BP, Mn-B@BP and Fe-B@BP) with low theoretical limiting potentials (-0.60, -0.41, -0.45, -0.43 and -0.50 V, respectively) and high selectivity for eNRR. We believe that the intermediate stabilization strategy introduced in current work offers a new opportunity to achieve accelerated and cost-effective ammonia synthesis with electrocatalysis.

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Conversion of CO2 to added value products via rWGS using Fe-promoted catalysts: Carbide, metallic Fe or a mixture? Qi Zhang, Laura Pastor-Pérez, Qiang Wang, Tomas Ramirez Reina 2022, 66(3): 635-646.  DOI: 10.1016/j.jechem.2021.09.015 Abstract ( 3 )   PDF (3134KB) ( 3 )   Fe-based catalysts are efficient systems for CO2 conversion via reverse water-gas shift (rWGS) reaction. Nevertheless, the nature of the active phase, namely metallic iron, iron oxide or iron carbide remains a subject of debate which our paper is meant to close. Fe0 is a much better catalyst for the rWGS than Fe3C. The activity of Fe0 can be promoted by the addition of Cs and Cu whose presence hinders iron carburisation while favouring both higher conversion and enhanced selectivity. When the samples are aged in the rWGS reaction mixture during stability test a new phase appear: Fe5C2, resulting in a more active but less selective catalysts than Fe0 for the rWGS reaction. Hence our results indicate that we could potentially achieve an optimal activity/selective balance upon finely tuning the proportion Fe/Fe5C2. Beyond the fundamental information concerning active phase we have observed the presence of advanced Fischer-Tropsch-like products at ambient pressure opening new opportunities for the design of hybrid rWGS/Fischer-Tropsch systems.

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Organic fast ion-conductor with ordered Li-ion conductive nano-pathways and high ionic conductivity for electrochemical energy storage Yibin Yang, He Zhou, Jiaying Xie, Lixia Bao, Tianshi Li, Jingxin Lei, Jiliang Wang 2022, 66(3): 647-656.  DOI: 10.1016/j.jechem.2021.09.011 Abstract ( 13 )   PDF (6145KB) ( 4 )   Solid electrolyte (SE) is the most crucial factor to fabricate safe and high-performance all-solid-state lithium-ion batteries. However, the most commonly reported SE, including solid polymer electrolyte (SPE) and inorganic oxides and sulfides, suffer problems of low ionic conductivity at room temperature for SPE and large interfacial impedance with electrodes for inorganic electrolytes. Here we for the first time demonstrate a novel ionic plastic crystal lithium salt solid electrolyte (OLiSSE) fast ion-conductor dilithium (1,3-diethyl-4,5-dicarboxylate) imidazole bromide with ordered Li-ion conductive nanopathways and an exceptional ionic conductivity of 4.4 × 10-3 S cm-1 at 30 °C. The prepared OLiSSE exhibits apparent characters of typical ionic plastic crystals in the temperature range of -20 to 70 °C, and shows remarkable thermal stability and electrochemical stability below 150 °C and 4.7 V, respectively. No lithium dendrite or short circuit behavior is detected for the Li|OLiSSE|Li cell after the galvanostatic charge-discharge test for 500 h. The fabricated Li|OLiSSE|LiFePO4 all-solid-state cell without using any separator and liquid plasticizer directly delivers an initial discharge capacity of 151.4 mAh g-1 at the discharge rate of 0.1 C, and shows excellent charge-discharge cycle stability, implying large potential application in the next generation of safe and flexible all-solid-state lithium batteries.

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Instant formation of excellent oxygen evolution catalyst film via controlled spray pyrolysis for electrocatalytic and photoelectrochemical water splitting Na An, Hengzheng Tian, Yang Zhou, Yalong Zou, Hao Xiu, Yufeng Cao, Ying Wang, Jianming Li, Deyu Liu, Yongbo Kuang 2022, 66(3): 657-665.  DOI: 10.1016/j.jechem.2021.09.023 Abstract ( 3 )   PDF (8010KB) ( 3 )   The retarded kinetics of oxygen evolution on electrodes is a bottleneck for electrochemical energy conversion and storage systems. NiFe-based electrocatalysts provide a cost-effective choice to confront this challenge. However, there is a lack of facile techniques for depositing compact catalytic films of high coverage and possessing a state-of-the-art performance, which is especially desired in photoelectrochemical (PEC) systems. Herein, we demonstrate a spray pyrolysis (SP) route to address this issue, featuring the kinetic selective preparation towards the desired catalytic-active material. Differing from reported SP protocols which only produce inactive oxides, this approach directly generates a unique composite film consisting of NiFe layered oxyhydroxides and amorphous oxides, exhibiting an overpotential as small as 255 mV (10 mA cm-2) and a turnover frequency of ∼0.4 s-1 per metal atom. By using such a facile protocol, the surface rate-limiting issue of BiVO4 photoanodes can be effectively resolved, resulting in a charge injection efficiency of over 90%. Considering this deposition directly start from simple nitrates but only takes several seconds to complete, we believe it can be developed as a widely applicable and welcomed functionalization technique for diverse electrochemical devices.

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Understanding Li roles in chemical reversibility of O2-type Li-rich layered cathode materials Jie Feng, Yun-Shan Jiang, Fu-Da Yu, Wang Ke, Lan-Fang Que, Jenq-Gong Duh, Zhen-Bo Wang 2022, 66(3): 666-675.  DOI: 10.1016/j.jechem.2021.08.064 Abstract ( 4 )   PDF (7349KB) ( 2 )   Traditional O3-type Li-rich layered materials are attractive with ultra-high specific capacities, but suffering from inherent problems of voltage hysteresis and poor cycle performance. As an alternative, O2-type materials show the potential to improve the oxygen redox reversibility and structural stability. However, their structure-performance relationship is still unclear. Here, we investigate the correlation between the Li component and dynamic chemical reversibility of O2-type Li-rich materials. By exploring the formation mechanism of a series of materials prepared by Na/Li exchange, we reveal that insufficient Li leads to an incomplete replacement, and the residual Na in the Li-layer would hinder the fast diffusion of Li+. Moreover, excessive Li induces the extraction of interlayer Li during the melting chemical reaction stage, resulting in a reduction in the valence of Mn, which leads to a severe Jahn-Teller effect. Structural detection confirms that the regulation of Li can improve the cycle stability of Li-rich materials and suppress the trend of voltage fading. The reversible phase evolution observed in in-situ X-ray diffraction confirms the excellent structural stability of the optimized material, which is conducive to capacity retention. This work highlights the significance of modulating dynamic electrochemical performance through the intrinsic structure.

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Gradient solid electrolyte interphase induced by bisfluoroacetamide for stable lithium metal batteries Qin Zhao, Tianyi Ma 2022, 66(3): 676-679.  DOI: 10.1016/j.jechem.2021.09.024 Abstract ( 6 )   PDF (3072KB) ( 5 )

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Phenylformamidinium-enabled quasi-2D Ruddlesden-Popper perovskite solar cells with improved stability Xingcheng Li, Wanpei Hu, Yanbo Shang, Xin Yu, Xue Wang, Weiran Zhou, Mingtai Wang, Qun Luo, Chang-Qi Ma, Yalin Lu, Shangfeng Yang 2022, 66(3): 680-688.  DOI: 10.1016/j.jechem.2021.09.026 Abstract ( 4 )   PDF (8113KB) ( 2 )   Two-dimensional (2D)/quasi-2D perovskite solar cells (PSCs) incorporating organic spacer cations exhibit appealing ambient stability in comparison with their 3D analogs. Most reported organic spacer cations are based on ammonium, whereas formamidinium (FA+) has been seldom applied despite that FA has been extensively used in high-efficiency 3D PSCs. Herein, a novel FA-based organic spacer cation, 4-chloro-phenylformamidinium (CPFA+), is applied in quasi-2D Ruddlesden-Popper (RP) PSCs for the first time, and methylammonium chloride (MACl) is employed to promote crystal growth and orientation of perovskite film, resulting in high power conversion efficiency (PCE) with improved stability. Upon incorporating CPFA+ organic spacer cation and MACl additive, high-quality quasi-2D CPFA2MAn-1Pbn(I0.857Cl0.143)3n+1 (n = 9) perovskite film forms, exhibiting improved crystal orientation, reduced trap state density, prolonged carrier lifetime and optimized energy level alignment. Consequently, the CPFA2MAn-1Pbn(I0.857Cl0.143)3n+1 (n = 9) quasi-2D RP PSC devices deliver a highest PCE of 14.78%. Moreover, the un-encapsulated CPFA-based quasi-2D RP PSC devices maintain ∼ 80% of its original PCE after exceeding 2000 h storage under ambient condition, whereas the 3D MAPbI3 counterparts retain only ∼ 45% of its original PCE. Thus, the ambient stability of quasi-2D RP PSC devices is improved obviously relative to its 3D MAPbI3 counterpart.