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2022, Vol. 73, No. 10　Online: 15 October 2022

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Unraveling the decomposition mechanism of Li2CO3 in the aprotic medium by isotope-labeled differential electrochemical mass spectrometry Lipo Ma, Aiping Wang, Shoufeng Zhang, Peng Zhang, Jiawei Wang 2022, 73(10): 1-4.  DOI: 10.1016/j.jechem.2022.05.045 Abstract ( 23 )   PDF (1165KB) ( 12 )

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Ultralong cycle life enabled by in situ growth of CoMo1-xP/Mo heterostructure for lithium-sulfur batteries Donghua Guo, Mengwei Yuan, Xingzi Zheng, Miaomiao Li, Caiyun Nan, Genban Sun, Xianqiang Huang, Huifeng Li 2022, 73(10): 5-12.  DOI: 10.1016/j.jechem.2022.05.025 Abstract ( 15 )   PDF (8506KB) ( 10 )   Lithium-sulfur batteries (Li-S batteries) are considered as promising new-generation electrochemical energy storage devices due to their extremely high theoretical energy density (2600 Wh kg-1) and theoretical specific capacity (1675 mAh g-1). However, numerous problems such as poor conductivity and the shuttle effect during discharge-charge process limit the practical application of lithium-sulfur batteries. In this work, porous tubular CoMo1-xP/Mo constructed by in situ growth of metal Mo was designed as the sulfur host for lithium-sulfur batteries. The introduction of Mo modulated the electronic structure of CoMoP to improve the conductivity of cathode and facilitate the redox kinetics, as well as the CoMo1-xP/Mo heterostructure was beneficial to inhibit the shuttle effect through the interaction with lithium polysulfides, which improved cycling stability. As a result, CoMo1-xP/Mo/S cathode had a low-capacity decay rate of only 0.029% per cycle after 2000 cycles at 0.5 C. This work provided a new perspective for the further design of high-performance lithium-sulfur battery cathode materials.

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A sustainable integration of removing CO2/NOx and producing biomass with high content of lipid/protein by microalgae Junying Zhu, Baowen Guo, Fengxiang Qie, Xu Li, Xikang Zhao, Junfeng Rong, Baoning Zong 2022, 73(10): 13-25.  DOI: 10.1016/j.jechem.2022.04.008 Abstract ( 14 )   PDF (251KB) ( 9 )   Due to the boost of CO2/NOx emissions which cause environmental pollution, processes that remove such pollutants from flue gas have attracted increasing attention in recent years. Among these technologies, biological CO2/NOx emission reduction has received more interest. Microalgae, a kind of photosynthetic microorganism, offer great promise to convert CO2/NOx to biomass with high content of lipid and protein, which can be used as feedstock for various products such as biodiesel, health products, feedstuff and biomaterials. In this paper, biological CO2/NOx removing technologies by microalgae, together with the products (such as biofuel and protein) and their economic viability are discussed. Although commercial applications of microalgae for biodiesel and protein products are hampered by the high production cost of biomass, the use of CO2/NOx from flue gas as carbon and nitrogen sources can reduce the cost of biomass production, which makes these technologies more competent for real-life applications. Moreover, it is projected that the increasing in CO2 allowances will lead to further reduction in the cost of biomass production, which especially favors related products with lower values such as biodiesel. Furthermore, by combining various process optimization and integration, biorefinery is proposed and considered as the crucial component for the sustainable and economically feasible bulk applications of microalgae biomass.

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Competing reduction induced homogeneous oxygen doping to unlock MoS2 basal planes for faster polysulfides conversion Da Lei, Wenzhe Shang, Xu Zhang, Yongpeng Li, Xiaoshan Shi, Shaoming Qiao, Qian Wang, Qiang Zhang, Ce Hao, Hui Xu, Guohua Chen, Gaohong He, Fengxiang Zhang 2022, 73(10): 26-34.  DOI: 10.1016/j.jechem.2022.06.002 Abstract ( 14 )   PDF (8766KB) ( 7 )   The parasitic polysulfides shuttle effect greatly hinders the practical application of lithium sulfur batteries, and this issue can be addressed by promoting polysulfides conversion with catalytic materials such as MoS2. However, the catalytic activity of MoS2 mainly relies on edge sites, but is limited by inert basal planes. We herein report a novel, facile, ethylene glycol enabled competing reduction strategy to dope MoS2 homogeneously with oxygen atoms so that its inert basal planes can be unlocked. Ethylene glycol works as a reducing agent and competes with thiourea to react with ammonium molybdate, leading to insufficient sulfuration of Mo, and consequent formation of O-MoS2. Our theoretical and experimental investigations indicate that the homogeneously distributed O dopants can create abundant adsorption/catalytic sites in the MoS2 basal planes, enlarge the inter-plane distance to promote ion transport, and thus enhance the catalytic conversion of polysulfides. The oxygen doped MoS2 (O-MoS2) is supported on carbon nanosheets (CNS) and the composite (O-MoS2/CNS) is employed to modify the separator of Li-S battery. It gives the battery an initial discharge capacity of 1537 mAh g-1 at 0.2 C, and the battery retains a discharge capacity of 545 mAh g-1 after ultra-long 2000 cycles at 1 C, corresponding to a very small cyclic decay rate of 0.0237%. Even under a raising sulfur loading of 8.2 mg cm-2, the Li-S battery also delivers a high discharge capacity (554 mAh g-1) with outstanding cycle stability (84.6% capacity retention) after 100 cycles at 0.5 C. Our work provides a novel, facile approach to fabricate highly catalytically active oxygen-doped MoS2 for advanced Li-S batteries.

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Effect of ultramicropores and inner space of carbon materials on the capacitive sodium storage performance Zimu Jiang, Su Zhang, Jing Feng, Yuting Jiang, Shichuan Liang, Qiqi Li, Mengjiao Shi, Meng Cao, Mingyi Zhang, Tong Wei, Zhuangjun Fan 2022, 73(10): 35-40.  DOI: 10.1016/j.jechem.2022.06.006 Abstract ( 29 )   PDF (3074KB) ( 14 )

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Hierarchical monolithic carbon with high transfer performance for hydrogen evolution reaction Yazhang Lin, Weijie Zhu, Yunhua Li 2022, 73(10): 41-48.  DOI: 10.1016/j.jechem.2022.05.019 Abstract ( 11 )   PDF (8863KB) ( 4 )   Electrocatalysis is an efficient green process for energy conversion. However, for gas-related electrocatalytic reaction, sluggish gas transport has inhibited significantly the promotion of electrocatalytic performances. Herein, hierarchical monolithic material 3DPC-650 and 3DPC-650@Ni/Ni(OH)2 were prepared by 3D printing polyethyleneimine cross-linking oxygenated carbon nanotube and following nickel electrodeposition. 3DPC-650 and 3DPC-650@Ni/Ni(OH)2 have regular pore structure in consistence with 3D printing design and uniform dispersed elements. Amide bonds and carbon defects are presented on the surface of 3DPC-650 and 3DPC-650@Ni/Ni(OH)2 as well as uniformly distributed β-Ni(OH)2 on 3DPC-650@Ni/Ni(OH)2. 3DPC-650 and 3DPC-650@Ni/Ni(OH)2 present lower overpotentials of 322 and 160 mV for hydrogen evolution reaction in 1.0 M KOH at 50 mA cm-2, respectively. The ordered channel, high turnover frequency and electrochemically active surface area, hydrophilic and aerophobic properties result in the higher performance of 3DPC-650 and 3DPC-650@Ni/Ni(OH)2 than traditional supports (carbon paper, carbon cloth, and nickel foam) and electrocatalysts. This work provides an efficient pathway for design and preparation of the monolithic electrocatalyst and electrode used for electrochemical reactions where gas is involved.

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Elucidating the effect of barium halide promoters on La2O3/CaO catalyst for oxidative coupling of methane Yue Wang, Xiao Yang, Fumin Yin, Kai Zhang, Hongfei Guo, Guowei Wang, Guiyuan Jiang, Chunyi Li, Xiaolin Zhu 2022, 73(10): 49-59.  DOI: 10.1016/j.jechem.2022.05.013 Abstract ( 6 )   PDF (10343KB) ( 9 )   The industrialization of oxidative coupling of methane (OCM) is restricted by the low once through yield of C2 hydrocarbons. Recently, the halogen-assisted OCM process has been attempted to overcome this issue, but the reaction stability was poor due to the rapid loss of gas-phase halides or molten alkali halides. In this work, the barium salts, particularly barium halides (BaCl2 and BaF2), were demonstrated to be efficient promoters to improve the OCM reactivity of La2O3/CaO catalyst by increasing both C2 selectivity and C2H4/C2H6 ratio, and simultaneously achieving outstanding reaction stability. The promoting mechanism can be understood in two aspects. On the one hand, the introduction of barium salts increased the amount of surface electrophilic oxygen species, serving as the alkaline active sites for selective methane activation. On the other hand, the barium halide additives induced the in-situ formation of methyl halide intermediates facilitating C2H6 dehydrogenation, and their intimate contact with catalyst substrate restricted the rapid halogen loss and thereby improved the catalytic stability. This work not only provides a class of efficient OCM catalyst, but also offers a highly stable halogen-assisted reaction strategy.

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Efficient plasmon-enhanced perovskite solar cells by molecularly isolated gold nanorods Yong Hui, En-Ming You, Qing-Peng Luo, Tan Wang, Zi-Ang Nan, Yu Gu, Wen-Han Zhang, Zhuan-Yun Cai, Liang Chen, Jian-Zhang Zhou, Jia-Wei Yan, Zhao-Xiong Xie, Bing-Wei Mao, Zhong-Qun Tian 2022, 73(10): 60-67.  DOI: 10.1016/j.jechem.2022.05.015 Abstract ( 11 )   PDF (8413KB) ( 4 )   Perovskite solar cells (PSCs) are becoming a promising candidate for next-generation photovoltaic cells due to their attractive power conversion efficiency (PCE). Plasmonic enhancement is regarded as an optical tuning approach for further improving the PCE of single-junction PSCs toward Shockley-Queisser limit. Herein, we introduce molecularly isolated gold nanorods (Au NRs), bearing relatively stronger scattering ability and localized surface plasmonic resonance (LSPR) effect, in the rear side of perovskites in PSCs, for promoting light harvesting and for electrical enhancement. Owing to the larger refractive index and better matched energy level alignment, the 4-mercaptobenzoic acid molecules coated on Au NRs prove to play important dual roles: isolating the metallic Au NRs from contacting with perovskite, and facilitating more efficient charge separation and transport across the interface under the synergetic LSPR effect of Au NRs. Our work highlights the capability of the plasmonic approach by nanorods and by molecular isolation, extending nanoparticle-based plasmonic approaches, toward highly efficient plasmon-enhanced PSCs.

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Molybdenum carbide as catalyst in biomass derivatives conversion Xiangze Du, Rui Zhang, Dan Li, Changwei Hu, Hermenegildo Garcia 2022, 73(10): 68-87.  DOI: 10.1016/j.jechem.2022.05.014 Abstract ( 14 )   PDF (17009KB) ( 8 )   The present energy dilemma in conjunction with the adverse environmental impacts caused by fossil fuel combustion motivates researchers to seek for new renewable energy with minimal CO2 footprint. As a practice pathway, it is of significance to produce biofuel and platform chemicals from sustainable biomass resources. However, the research and development of high-efficiency catalysts remain one key scientific challenge. Among the catalysts developed, transition metal carbides, especially molybdenum carbide, show promising performances on biomass-based conversion. Significant efforts have been made in past few decades on tuning the structure and electronic property of molybdenum carbide via controlling particle size and morphology, metal and nonmetal doping and vacancies, etc. The review summarizes recent developments of molybdenum carbide as catalysts in converting biomass into fuel, mainly focused on the preparation methods, the structure-dependent effects and the electronic modulation. The controllable selective cleavage of C-C, C-O and C-H bonds over modified molybdenum carbides that has been demonstrated in the conversion of biomass feedstocks is then highlighted. In addition, the possible deactivation mechanisms of molybdenum carbide are also presented in the review. This review provides systematic and fundamental information for the further design and development of molybdenum carbide for the conversion of biomass resources.

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Current trending and beyond for solar-driven water splitting reaction on WO3 photoanodes Magno B. Costa, Moisés A. de Araújo, Marcos V. de Lima Tinoco, Juliana F. de Brito, Lucia H. Mascaro 2022, 73(10): 88-113.  DOI: 10.1016/j.jechem.2022.06.003 Abstract ( 18 )   PDF (11343KB) ( 5 )   This review shows the importance of WO3 photoanode as a potentially low-cost, efficient, stable, and photoactive material for light-driven water splitting. For such, this manuscript aims to review the most recent publications regarding the strategies to improve the phoelectroactivity of WO3 films for water oxidation. In addition, this review aims to graphically highlight and discuss the general trendings of the photocurrent density response and stability test of the recent outstanding studies in the literature for photoelectrochemical water splitting application. The strategies covered in this review will not only concern the WO3 morphology and crystal plane growth, but also the many arrangements possibilities to improve the WO3 efficiency for water photoelectrooxidation, such as defect engineering based on oxygen vacancies, doping, decorations, and homo and heterojunctions. All these strategies are compared by the photocurrent density results and by the stability of these photocatalysts. The best results in this sense were observed in cases where the use of heterojunction was applied together with a desired morphology and crystal plane of the WO3 photoanode. However, the modifications that caused a decrease in the photocurrent density reaching values that are even lower than the pure WO3 were also discussed. In this way, this review intends to improve the knowledge about the synthesis and design of WO3 photoanodes to further obtain an efficient photocatalyst to minimize the recombination losses or losses across the interfaces and improve the photoelectroactivity for water splitting in the large-scale application.

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Construction of internal electric field to suppress oxygen evolution of Ni-rich cathode materials at a high cutoff voltage Youqi Chu, Anjie Lai, Qichang Pan, Fenghua Zheng, Youguo Huang, Hongqiang Wang, Qingyu Li 2022, 73(10): 114-125.  DOI: 10.1016/j.jechem.2022.06.019 Abstract ( 14 )   PDF (4884KB) ( 4 )   The Nickel-rich layered cathode materials have been considered as promising cathode for lithium-ion batteries (LIBs), which due to it can achieve a high capacity of than 200 mAh g-1 under a high cutoff voltage of 4.5 V. However, the nickel-rich layered cathode materials show severely capacity fading at high voltage cycling, induced by the hybrid O anion and cation redox promote Oα- (α< 2) migration in the crystal lattice under high charge voltage, lead to the instability of the oxygen skeleton and oxygen evolution, promote the phase transition and electrolyte decomposition. Here, Li1-xTMO2-y/Li2SO4 hybrid layer is designed by a simple pyrolysis method to enhance the high voltage cycle stability of NCM. In such constructed hybrid layer, the inner spinel structure of Li1-xTMO2-y layer is the electron-rich state, which could form an electron cloud coupling with the NCM with surface oxygen vacancies, while Li2SO4 is p-type semiconductors, thus constructing a heterojunction interface of Li1-xTMO2-y//Li2SO4 and Li1-xTMO2-y//NCM, thereby generating internal self-built electric fields to inhibit the outward migration of bulk oxygen anions. Moreover, the internal self-built electric fields could not only strengthen the bonding force between the Li1-xTMO2-y/Li2SO4 hybrid layer and host NCM material, but also boost the charge transfer. As consequence, the modified NCM materials show excellent electrochemical performance with capacity retention of 97.7% and 90.1% after 200 cycles at 4.3 V and 4.5 V, respectively. This work provides a new idea for the development of high energy density applications of Nickel-rich layered cathode materials.

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Synthesis of multicore-shell FeS2@C nanocapsules for stable potassium-ion batteries Zhuangzhuang Zhang, Liping Duan, Yifan Xu, Chuanfeng Zhao, Jianchun Bao, Jian Shen, Xiaosi Zhou 2022, 73(10): 126-132.  DOI: 10.1016/j.jechem.2022.04.039 Abstract ( 7 )   PDF (5247KB) ( 2 )   Transition-metal sulfides are widely used as anodes for potassium-ion batteries (PIBs) due to their low cost and high theoretical capacity. The practical application of such materials, however, is still impeded by their inherent low conductivity and obvious volume change during cycling. Herein, a flexible etch-assisted sulfidation strategy is reported. According to the strategy, the multicore-shell (MCS) nanocapsule structure is constructed, and then mesoporous FeS2 nanoparticles are encapsulated in the hollow carbon shell with adjustable interior space. The product, MCS-FeS2@C-20, not only features optimized inner space, but also delivers a large reversible capacity (519 mAh g-1 at a current density of 50 mA g-1), good rate capability (107 mAh g-1 at a high current density of 5 A g-1) and excellent cycling stability (capacity retention rate of 84.2% over 500 cycles at 0.5 A g-1), making it the promising anode material for PIBs. Notably, potassium-ion full cells (MCS-FeS2@C-20//K0.4CoO2) also show an improved potassium storage performance.

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Alcohol-assisted hydrodeoxygenation as a sustainable and cost-effective pathway for biomass derivatives upgrading Hao Xu, Hao Li 2022, 73(10): 133-159.  DOI: 10.1016/j.jechem.2022.05.021 Abstract ( 9 )   PDF (17074KB) ( 3 )   Hydrodeoxygenation (HDO) is one of the most promising strategies for the upgrading of biomass-derived compounds to chemicals and fuels. However, the conventional HDO process accompanied by insecure high-pressure H2 leads to the hefty infrastructure cost on the industrial scale and inevitably trigger overall hydrogenation which is considered as an uncontrollable and risky approach. Accordingly, the developments of alcohol-assisted HDO can be viewed as a sustainable and cost-effective alternative. This review critically summarizes the potentials and challenges of alcohol-assisted strategy from diverse perspectives including safety, economics and catalytic efficiency. Based on the discrepancies of in-situ hydrogen generation, the alcohol-assisted strategy is divided into combined reforming-HDO route and catalytic transfer hydrogenation/hydrogenolysis (CTH) route. Furthermore, describe different catalytic behaviors and elaborate their applications among several upgrading processes of representative biomass model compounds, aiming to illustrate their potentials in biomass utilization. The influence of alcohols is highlighted because they act both hydrogen donor and solvent. At last, the current challenges and perspectives of alcohol-assisted HDO are proposed for further development and improvement.

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Approaches for enhancing the photocatalytic activities of barium titanate: A review Gopal Panthi, Mira Park 2022, 73(10): 160-188.  DOI: 10.1016/j.jechem.2022.06.023 Abstract ( 20 )   PDF (6885KB) ( 10 )   Barium titanate (BaTiO3), a dielectric/ferroelectric semiconductor with perovskite structures is the most widely used photocatalyst in the field of environmental applications due to its low-cost, chemical stability, and non-toxicity. Different types and forms of BaTiO3 have shown their great potential toward the significant photocatalytic reactions owing to the several beneficial properties, including appropriate band positions, high oxygen vacancies, multiple crystal structures, the feasibility of size and morphology tailoring, spontaneous polarization, rapid migration of photogenerated charge carriers, and band bending. However, the large band gap and recombination of photogenerated charge carriers limit the overall photocatalytic efficiency of BaTiO3. These difficulties can be further overcome by modifying the electronic band structure of BaTiO3 to broaden its absorption to the visible region of the spectrum. Hence, this review encompasses various strategies, including modification of sizes and morphologies of particles by varying the reaction time and synthesis temperature, doping with non-metals/metals, loading with noble metals, and forming heterojunctions for enhancing the photocatalytic activities of BaTiO3-based photocatalysts possessing the effective capability of charge carrier separation, trapping and their transfer to the surface of photocatalyst. Also, this review highlights the photocatalytic applications of BaTiO3-based photocatalysts along with the proposed mechanism in dyes/drugs degradation, H2 production, and bacteria killing.

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Metal chalcogenide-based photoelectrodes for photoelectrochemical water splitting Marwa Mohamed Abouelela, Go Kawamura, Atsunori Matsuda 2022, 73(10): 189-213.  DOI: 10.1016/j.jechem.2022.05.022 Abstract ( 11 )   PDF (9237KB) ( 5 )   Photoelectrochemical water splitting (PEC-WS) is a promising technique for transforming solar energy into storable and environmentally friendly chemical energy. Designing semiconductor photoelectrodes with high light absorption capability, rapid e-/h+ separation and transfer, and sufficient chemical stability is vital for developing an efficient PEC-WS system. Metal chalcogenides (MCs) have emerged as promising candidates for light absorbers because of their unique electrical and optical characteristics. In this review, we present recent developments in hydrogen generation via PEC-WS using MC-based photoelectrodes. First, we present a simple illustration of PEC-WS fundamentals. Second, the current performance of various metal (mono-, di-, and tri-) chalcogenide/semiconductor photoelectrodes in PEC-WS is summarized. Then, the charge transfer mechanism at the MC/semiconductor interface and the PEC-WS mechanism is thoroughly explained. Finally, we discuss future research perspectives toward developing efficient and stable MC/semiconductor photoelectrodes.

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Tuning anionic redox activity to boost high-performance sodium-storage in low-cost Na0.67Fe0.5Mn0.5O2 cathode Jianyue Jiao, Kang Wu, Na Li, Enyue Zhao, Wen Yin, Zhongbo Hu, Fangwei Wang, Jinkui Zhao, Xiaoling Xiao 2022, 73(10): 214-222.  DOI: 10.1016/j.jechem.2022.04.042 Abstract ( 16 )   PDF (8998KB) ( 11 )   Na-based layered iron-manganese oxide Na0.67Fe0.5Mn0.5O2 containing only low-cost elements is a promising cathode for Na-ion batteries used in large-scale energy storage systems. However, the poor cycle stability restricts its practical application. The capacity decay of Na0.67Fe0.5Mn0.5O2 mainly originates from the irreversible anionic redox reaction charge compensation due to the high-level hybridization between oxygen and iron. Herein, we rationally design a surface Ti doping strategy to tune the anionic redox reaction activity of Na0.67Fe0.5Mn0.5O2 and improve its Na-storage properties. The doped Ti ions not only enlarge the Na migration spacing layer but also improve the structure stability thanks to the strong Ti-O bond. More importantly, the d0-shell electronic structure of Ti4+ can suppress the charge transfer from the oxidized anions to cations, thus reducing the anionic redox reaction activity and enhancing the reversibility of charge compensation. The modified Na0.67Fe0.5Mn0.5O2 cathode shows a reversible capacity of 198 mA h g-1 and an increased capacity retention from 15% to 73% after about 1 month of cycling. Meanwhile, a superior Na-ion diffusion kinetics and rate capability are also observed. This work advances the commercialization process of Na-based layered iron-manganese oxide cathodes; on the other hand, the proposed modification strategy paves the way for the design of high-performance electrode materials relying on anionic redox reactions.

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From protonation & Li-rich contamination to grain-boundary segregation: Evaluations of solvent-free vs. wet routes on preparing Li7La3Zr2O12 solid electrolyte Xiao Huang, Yang Lu, Yajun Niu, Jiawen Tang, Yongjian Zhou, Yan Yang, Bingbing Tian 2022, 73(10): 223-239.  DOI: 10.1016/j.jechem.2022.05.036 Abstract ( 5 )   PDF (13967KB) ( 2 )   Garnet-type Li7La3Zr2O12 (LLZO) has been recognized as a candidate solid electrolyte for high-safety Li-anode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent (e.g., isopropanol (IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of as-calcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets, the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations (e.g., LiOH∙H2O and Li2CO3) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.

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Accelerated intermediate conversion through nickel doping into mesoporous Co-N/C nanopolyhedron for efficient ORR Jianxin Mao, Peng Liu, Jiawen Li, Jianyue Yan, Shen Ye, Wenbo Song 2022, 73(10): 240-247.  DOI: 10.1016/j.jechem.2022.04.047 Abstract ( 4 )   PDF (7396KB) ( 2 )   Engineering non-precious metals into nitrogen-doped carbon is employed to improve electrocatalyst activity towards oxygen reduction reaction (ORR). A nickel-doped Co-N/C mesoporous nanopolyhedron is successfully evoluted from a Ni-doped ZIF-67 precursor. The Ni & Co synergistic N/C catalyst exhibits a half-wave potential of 0.895 V (vs. reversible hydrogen electrode (RHE)) with a diffusion-limiting current density of 6.1 mA cm-2 for alkaline ORR at 1600 r min-1, which is competitive to commercial Pt/C in terms of cost, methanol tolerance, and long-term stability. In situ surface-enhanced Raman scattering (SERS) study reveals the formation and fast conversion of superoxide ion (O2-) intermediate on the catalyst surface. Density functional theory (DFT) calculations demonstrate the decrease of energy barrier for potential-determining step (O* protonation) by Co-Ni synergy as well as the reduction of adsorption energy on catalyst surface upon nickel doping. The joint results of in situ SERS study and DFT calculations suggest a favourable ORR process on nickel-doped Co-N/C.

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Protein-modified SEI formation and evolution in Li metal batteries Chenxu Wang, Ryan Odstrcil, Jin Liu, Wei-Hong Zhong 2022, 73(10): 248-258.  DOI: 10.1016/j.jechem.2022.06.017 Abstract ( 12 )   PDF (12676KB) ( 7 )   Despite numerous reported lithium metal batteries (LMBs) with excellent cycling performance achieved in labs, transferring the high performing LMBs from lab-scale to industrial-production remains challenging. Therefore, via imitating the stand-still process in battery production, a conventional but important procedure, to investigate the formation and evolution of a solid electrolyte interface (SEI) is particularly important for LMBs. Our previous studies indicate that zein (corn protein)-modified carbonate-ester electrolyte (the most commercialized) effectively improves the performance of LMBs through guiding Li-ions and repairing cracked SEI. Herein, we investigate the formation and evolution of the protein-modified SEIs on Li anodes by imitating the stand-still temperature and duration. A simulation study on the protein denaturation in the electrolyte under different temperatures demonstrates a highly unfolded configuration at elevated temperatures. The experiments show that this heat-treated-zein (H-zein) modified SEI forms quickly and becomes stable after a stand-still process of less than 100 min. Moreover, the H-zein SEI exhibits excellent wetting behavior with the electrolyte due to the highly unfolded protein structures with more functional groups exposed. The Li|Li cell with the H-zein SEI achieves prolonged cycling performance (>360 h vs. ∼260 h of the cell with the untreated-zein (U-zein) modified SEI). The LiFePO4|Li cell with the H-zein SEI shows much stable long-term cycling performance of capacity retention (70% vs. 42% of the cell with U-zein SEI) after 200 cycles. This study confirms that the appropriately treated protein is able to effectively improve the performance of LMBs, and will inspire future studies for the production process of LMBs toward their commercialization.

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Water promoted photocatalytic transfer hydrogenation of furfural to furfural alcohol over ultralow loading metal supported on TiO2 Shuang Lv, Huifang Liu, Jian Zhang, Qiang Wu, Feng Wang 2022, 73(10): 259-267.  DOI: 10.1016/j.jechem.2022.06.012 Abstract ( 21 )   PDF (7526KB) ( 13 )   Photocatalytic hydrogenation of furfural offers an ideal method for selective biomass upgrading into value-added chemicals or fuel additives under mild conditions. However, it is still challenging to control the product selectivity due to side reactions of functional groups and reactive radical intermediates. Herein, photocatalytic transfer hydrogenation of furfural was studied using the TiO2-based photocatalysts with alcohols as both the solvent and hydrogen donor. Ultralow loading metal supported on TiO2, together with adding a small amount of water in the system, were demonstrated to greatly increase the selectivity of furfuryl alcohol product. Electron paramagnetic resonance (EPR), ultraviolet-visible spectroscopy (UV-Vis) and photoluminescence (PL) measurements gave evidence that ultralow loading Pt or Pd on TiO2 increase the oxygen vacancy concentration and the photogenerated charge separation efficiency, which accelerates the photocatalytic reduction of furfural. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mechanistic studies confirmed that photogenerated holes and electrons are active species, with dissociatively adsorbed methanol being directly oxidized by holes, furfural hydrogenated by protons and electrons and H2O modifying the intermediate diffusion which contributes to high selectivity of furfuryl alcohol. This work demonstrates a simple approach to design photocatalysts and tune product selectivity in biomass valorization.

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Lithiophilic seeds and rigid arrays synergistic induced dendrite-free and stable Li anode towards long-life lithium-oxygen batteries Yue Li, Haichang Zhang, Rui Zhang, Junwei Sha, Liying Ma, Dongdong Zhao, Chunsheng Shi, Naiqin Zhao 2022, 73(10): 268-276.  DOI: 10.1016/j.jechem.2022.06.021 Abstract ( 8 )   PDF (11695KB) ( 2 )   High energy density lithium-oxygen battery (LOB) is currently regraded as a promising candidate for next-generation power system. However, the dendrite and instability issues of Li metal anode lead to its poor cyclic stability and low energy density. In this work, lithiophilic Al2O3 seeds induced rigid carbon nanotube arrays (CNTA)/three-dimensional graphene (3DG) is developed as a host material for Li anode, namely Al2O3-CNTA/3DG. It is demonstrated that the lithiophilic feature of Al2O3 seeds and the enhanced rigidity of arrays can synergistically induce the uniform Li flux, inhibit the collapse of arrays, and stabilize electrolyte/electrode interfaces. As a result, the Al2O3-CNTA/3DG-Li anode delivers a high Coulombic efficiency above 97% after 140 cycles (8 mAh cm-2 at 4 mA cm-2). With this anode and the breathable CNTA/3DG cathode, the full LOB exhibits a significantly increased life-span up to 160 cycles (500 mAh g-1 at 100 mA g-1), which is almost 3 times longer than that with pure Li foil as the anodes. This work demonstrates a new approach to highly reversibly long-cycling performance of LOBs towards practical application.

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MXene-assisted polymer coating from aqueous monomer solution towards dendrite-free zinc anodes Ning Wang, Zhitan Wu, Yu Long, Derong Chen, Chuannan Geng, Xiaochen Liu, Daliang Han, Jing Zhang, Ying Tao, Quan-Hong Yang 2022, 73(10): 277-284.  DOI: 10.1016/j.jechem.2022.06.009 Abstract ( 8 )   PDF (5356KB) ( 4 )   Coating polymer on the surface is an effective way to realize functional modification of the materials for diverse applications, which has been proved to enhance the stability of metal anodes in batteries. However, given the limited operability of coating from polymer dispersions, it is imperative to develop simple aqueous-based strategies from monomers for versatile polymer coating. Herein, a Ti3C2Tx MXene-assisted approach is proposed to construct polymer coating on zinc metal surfaces directly from the aqueous solution of monomers in an ice bath. By combining a doctor-blading method with spontaneous polymerization of monomers on the substrates at room temperature, a uniform, adhesive, and versatile coating layer assisted by a small amount of MXene is produced in one step. Additionally, MXene nanosheets serve as nanofillers to further enhance the mechanical strength and ionic conductivity of the polymer coating. Benefiting from good film formation and improved interfacial contact, the coated zinc anode exhibits a long cycling lifespan of over 1900 h. The assembled full cells show excellent cycling stability with a high capacity retention of 85.0% at 16 A g-1 over 2600 cycles. This work provides a simple and efficient way to produce polymer coatings directly from monomers, which may give new insights into design multifunctional polymer coatings for various applications.

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Driving lithium to deposit inside structured lithium metal anodes: A phase field model Rui Zhang, Xin Shen, Hao-Tian Ju, Jun-Dong Zhang, Yu-Tong Zhang, Jia-Qi Huang 2022, 73(10): 285-291.  DOI: 10.1016/j.jechem.2022.06.010 Abstract ( 8 )   PDF (4715KB) ( 4 )   Lithium metal anode is one of the most important anode materials for next-generation high-specific-energy secondary batteries. Structured lithium metal anodes have received extensive attention in the development of practical lithium metal batteries. Methods of driving lithium metal to deposit inside the pores of structured lithium metal anodes have always been one of the most concerned issues, especially for highly conductive frameworks. An electrochemical phase field theory with galvanostatic lithium plating process is employed in this work, the mechanism that illustrates the preference of lithium metal to deposit at the top of the framework structure has been revealed, and through the simulation analysis of various regulating strategies, the strategies that can efficiently drive lithium to deposit inside structured pores are summarized. This work presents the theoretical calculation and analysis methods that can be used for the rational design of lithium metal batteries.

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Towards electrochemical hydrogen storage in liquid organic hydrogen carriers via proton-coupled electron transfers Hamid Ghorbani Shiraz, Mikhail Vagin, Tero-Petri Ruoko, Viktor Gueskine, Krzysztof Karoń, Mieczys ławŁapkowski, Tobias Abrahamsson, Thomas Ederth, Magnus Berggren, Xavier Crispin 2022, 73(10): 292-300.  DOI: 10.1016/j.jechem.2022.06.015 Abstract ( 24 )   PDF (5615KB) ( 6 )   Green hydrogen is identified as one of the prime clean energy carriers due to its high energy density and a zero emission of CO2. A possible solution for the transport of H2 in a safe and low-cost way is in the form of liquid organic hydrogen carriers (LOHCs). As an alternative to loading LOHC with H2 via a two-step procedure involving preliminary electrolytic production of H2 and subsequent chemical hydrogenation of the LOHC, we explore here the possibility of electrochemical hydrogen storage (EHS) via conversion of proton of a proton donor into a hydrogen atom involved in covalent bonds with the LOHC (R) via a proton-coupled electron transfer (PCET) reaction: $2 n H^{+}+2 n e^{-}+R_{\mathrm{ox}} \leftrightarrow n H_2^0 R_{\text {red }}$. We chose 9-fluorenone/fluorenol (Fnone/Fnol) conversion as such a model PCET reaction. The electrochemical activation of Fnone via two sequential electron transfers was monitored with in-situ and operando spectroscopies in absence and in presence of different alcohols as proton donors of different reactivity, which enabled us to both quantify and get the mechanistic insight on PCET. The possibility of hydrogen extraction from the loaded carrier molecule was illustrated by chemical activation.

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Development of covalent-organic frameworks derived hierarchical porous hollow carbon spheres based LiOH composites for thermochemical heat storage Xiangyu Yang, Shijie Li, Jianguo Zhao, Hongyu Huang, Lisheng Deng 2022, 73(10): 301-310.  DOI: 10.1016/j.jechem.2022.06.022 Abstract ( 7 )   PDF (9495KB) ( 3 )   Under the joint assistance of its excellent storage strength, accessible long storage lifespan, and high heat utilization efficiency, salt hydrate-based thermochemical heat storage (THS) materials give renewable energy an important outlet to alleviate the pressure of underutilization. Herein, an activated hollow spherical carbon (AHSC) with hierarchical porous architectures converted from covalent-organic frameworks (COFs) is constructed and utilized as the supporting matrix for LiOH·THS composite material for the first time. The obtained Li/AHSC3 composites have distinguished hydration performance while manifesting impressive storage ability up to 1916.4 kJ kg-1 with low operating temperature stemming from the collective effect of the void spherical framework, multimodal porosity, and high surface area of AHSC3. And the Li/AHSC3-40 composite with evidently progressed thermal conductivity is capable of realizing 94.5% heat preservation after twenty-five adsorption-desorption cycles, exhibiting its eminent cyclability and great heat transfer performance. This study not only brings new hope for overcoming the underutilization of low-grade heat but also may enlighten new ideas for enriching the application scenarios of COFs-derived carbonaceous materials.

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A cerium-doped NASICON chemically coupled poly(vinylidene fluoride-hexafluoropropylene)-based polymer electrolyte for high-rate and high-voltage quasi-solid-state lithium metal batteries Tao Huang, Wei Xiong, Xue Ye, Zhencheng Huang, Yuqing Feng, Jianneng Liang, Shenghua Ye, Jishou Piao, Xinzhong Wang, Yongliang Li, Xiangzhong Ren, Chao Chen, Shaoluan Huang, Xiaoping Ouyang, Qianling Zhang, Jianhong Liu 2022, 73(10): 311-321.  DOI: 10.1016/j.jechem.2022.06.030 Abstract ( 17 )   PDF (9924KB) ( 6 )   The isolated inorganic particles within composite polymer electrolytes (CPEs) are not correlated to the Li+ transfer network, resulting in the polymer dominating the low ionic conductivity of CPEs. Therefore, we developed novel quasi-solid-state CPEs of a Ce-doped Na super ion conductors (NASICON) Na1.3+xAl0.3CexTi1.7-x(PO4)3 (NCATP) chemically coupled poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP)/Li-bis(trifluoromethanes-ulfonyl)imide (LiTFSI) matrix. A strong interaction between Ce3+ from NCATP and TFSI- anion from the polymer matrix contributes to the fast Li+ transportation at the interface. The PVDF-HFP/NCATP CPEs exhibit an ionic conductivity of 2.16 × 0-3 S cm-1 and a Li+ transference number of 0.88. A symmetric Li/Li cell with NCATP-integrated CPEs at 0.1 mA cm-2 presents outstanding cycling stability over 2000 h at 25 °C. The quasi-solid-state Li metal batteries of Li/CPEs/LiFePO4 at 2 C after 400 cycles and Li/CPEs/LiCoO2 at 0.2 C after 120 cycles deliver capacities of 100 and 152 mAh g-1 at 25 °C, respectively.

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Co2P nanorods with exposure of high-index facets for efficient photochemical reduction of CO2 by promoting the directional transfer of electrons Yong Xu, Jiang Mo, Jianfei Long, Lingxiao Tu, Weili Dai, Lixia Yang, Shenglian Luo 2022, 73(10): 322-329.  DOI: 10.1016/j.jechem.2022.06.018 Abstract ( 6 )   PDF (7395KB) ( 3 )   Herein, Co2P nanorods (NRs) with exposure to high-index facets (HIFs) were prepared by a special assembly-calcination method using thioacetamide (TAA) as a structure-directing reagent. The analysis of adsorption energies of S atoms on different facets as well as the surface energies of Co2P indicate that the HIFs become more stable after adsorbing S atoms. With rich unsaturated sites on HIFs, the photochemical reduction rate of CO2 over Co2P NRs is 14.5 mmol h-1 g-1 for the production of CO within 3 h. The analysis of electron transfer, bond lengths, bond angles and adsorption energies indicate that the CO2 molecules are more easily adsorbed and activated on the HIFs. The free energy calculations and d band theory demonstrate that the HIFs are conducive to reducing the formation energy barriers as well as improving the stability of the intermediate *COOH, then enhancing the catalytic performance of CO2 reduction.

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Tailoring interfacial electron redistribution of Ni/Fe3O4 electrocatalysts for superior overall water splitting Wenli Xu, Wenda Zhong, Chenfan Yang, Rong Zhao, Jing Wu, Xuanke Li, Nianjun Yang 2022, 73(10): 330-338.  DOI: 10.1016/j.jechem.2022.06.042 Abstract ( 10 )   PDF (5832KB) ( 4 )   Exploring highly active earth-abundant bifunctional electrocatalysts for water splitting at a high output is essential for the forthcoming hydrogen economy. Non-noble Fe3O4 catalyst owns outstanding conductivity and its octahedral Fe sites can markedly promote water dissociation. However, it lacks active centers on the surface, resulting in its poor activity when used as a catalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, an electron redistribution strategy is proposed by introducing Ni sites onto the surface of Fe3O4 (Ni/Fe3O4). The abundant delocalized electrons, derived from the electronic interaction of Ni and Fe3O4 species, significantly optimize the electronic structure of the Ni/Fe3O4 catalyst, leading to its improved adsorption behavior. This Ni/Fe3O4 catalyst exhibits remarkable bifunctional activity, steadily outputting 1000 mA cm-2 at the low overpotential of 387 mV for HER and 338 mV for OER, respectively. Using Ni/Fe3O4 as a bifunctional catalyst for overall water splitting reaction exhibits the optimal performance with outstanding stability, obtaining a current density of 1000 mA cm-2 at 1.98 V, much superior to a Pt/C||IrO2 cell. Experimental analysis and theoretical calculations collectively corroborate that the electron redistribution of Fe3O4 is activated by coupling Ni species, leading to the promoted HER and OER kinetics. This electron redistribution strategy provides an effective method to activate transition metal-based catalysts which are promising to be utilized as superior electrocatalysts for the industrial overall water splitting reaction.

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In situ formation of lithiophilic Li22Sn5 alloy and high Li-ion conductive Li2S/Li2Se via metal chalcogenide SnSSe for dendrite-free Li metal anodes Yaya Wang, Yang Guo, Jiang Zhong, Meng Wang, Lei Wang, Shengyang Li, Song Chen, Hongli Deng, Yong Liu, Yidi Wu, Jian Zhu, Bingan Lu 2022, 73(10): 339-347.  DOI: 10.1016/j.jechem.2022.06.039 Abstract ( 9 )   PDF (8400KB) ( 5 )   Lithium metal has gained extensive attention as the most ideal candidate for next-generation battery anode owing to the ultrahigh specific capacity and the lowest electrochemical potential. However, uncontrollable dendrite growth and huge volume variation extremely restrict the future deployment of lithium metal batteries. Herein, we report metal chalcogenide SnSSe with unique nanoplate stacking structure as a robust substrate for stable Li metal anode. During the initial Li plating process, lithiophilic Li22Sn5 alloy and Li2S/Li2Se sites are obtained via in-situ electrochemical reaction of Li metal and SnSSe. Density functional theory (DFT) calculation demonstrates that the formed Li2S/Li2Se achieves low Li diffusion energy barrier, ensuring rapid Li+ migration. Li22Sn5 alloy provides strong nucleation sites, promoting uniform Li nucleation. Furthermore, in-situ optical microscopy analysis suggests that the synthesized effect fundamentally inhibits lithium dendrite growth. Consequently, SnSSe modified Cu foil delivered an ultralow nucleation overpotential, superior cycling stability with 450 cycles (Coulombic efficiency, >98%), and excellent plating/stripping behavior over 2200 h at 0.5 mA cm-2. Moreover, the brilliant reversible cycles and rate capability were also realized in Li@SnSSe//LiFePO4 (LFP) full cell, shedding light on the feasibility of SnSSe for stable and dendrite-free lithium metal anode.

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Performance and potential of porous carbons derived of electrospun metal-organic frameworks for supercapacitor applications Petra Ágota Szilágyi, Ana Jorge Sobrido 2022, 73(10): 348-353.  DOI: 10.1016/j.jechem.2022.06.029 Abstract ( 11 )   PDF (7740KB) ( 7 )

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Revealing the dominant factor of domain boundary resistance on bulk conductivity in lanthanum lithium titanates Xuefeng Zhou, Cong Gao, Dandan Wang, Shang Peng, Lujun Huang, Wenge Yang, Wen-Hua Zhang, Xiang Gao 2022, 73(10): 354-359.  DOI: 10.1016/j.jechem.2022.06.020 Abstract ( 12 )   PDF (4602KB) ( 14 )   Perovskite-type lithium lanthanum titanates (LLTO) display a high bulk ionic conductivity and are considered a promising electrolyte for building up to advanced solid-state Li-ion batteries. The LLTO crystals contain a high concentration of intrinsically formed 90°-rotated domain boundaries (DBs) serving as barriers to bulk Li-ion conduction. However, the mechanism of how the DB concentration and DB resistance can compete with each other to determine the bulk conductivity of LLTO is still unknown. Here we report a comprehensive study of LLTO compounds, aimed to unravel the mechanism and hence explore new path(s) for further improving the conductivity of this material. Our results show that both the sintering temperature and chemical composition can affect significantly the domain structures in LLTO. It is found that a decrease in the DB concentration is always accompanied by increased DB resistance due to the increased lattice mismatch at DBs, and vice versa. By unifying the electrochemical impedance spectroscopy and transmission electron microscopy analysis, it is clearly shown that the high DB resistance, instead of DB concentration, acts as the dominant factor governing the bulk conductivity of LLTO. The results thus renew the conventional understanding of the bulk Li-ion conduction in LLTO and shed light on developing novel LLTO electrolyte materials with improved ionic conductivity.

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Poly(carbonate)-based ionic plastic crystal fast ion-conductor for solid-state rechargeable lithium batteries He Zhou, Jiaying Xie, Lixia Bao, Sibo Qiao, Jiefei Sui, Jiliang Wang 2022, 73(10): 360-369.  DOI: 10.1016/j.jechem.2022.06.038 Abstract ( 6 )   PDF (5602KB) ( 2 )   Liquid plasticizers with a relatively higher dielectric coefficient like ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) are the most commonly used electrolyte materials in commercial rechargeable lithium batteries (LIBs) due to their outstanding dissociation ability to lithium salts. However, volatility and fluidity result in their inevitable demerits like leakage and potential safety problem of the final LIBs. Here we for the first time device a subtle method to prepare a novel thermal-stable and non-fluid poly(carbonate) solid-state electrolyte to merge EC with lithium carriers. To this aim, a series of carbonate substituted imidazole ionic plastic crystals (G-NTOC) with different polymerization degrees have been synthesized. The resulting G-NTOC shows an excellent solid-state temperature window (R.T.-115 °C). More importantly, the maximum ionic conductivity and lithium transference number of the prepared G-NTOC reach 0.36 × 10-3 S cm-1 and 0.523 at 30 °C, respectively. Galvanostatic cycling test results reveal that the developed G-NTOC solid-state electrolytes are favorable to restraining the growth of lithium dendrite due to the excellent compatibility between the electrode and the produced plastic crystal electrolyte. The fabricated Li|G-NTOC|LiFePO4 all-solid-state cell initially delivers a maximum discharge capacity of 152.1 mAh g-1 at the discharge rate of 0.1C. After charging-discharging the cell for 60 times, Coulombic efficiency of the solid-state cell still exceeds 97%. Notably, the Li|G-NTOC|LiFePO4 cell can stably light a commercial LED with a rated power of 0.06 W for more than 1 h at 30 °C, and the output power nearly maintains unchanged with the charging-discharging cycling test, implying a sizeable potential application in the next generation of solid-state LIBs.

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Solid-state electrolytes for solid-state lithium-sulfur batteries: Comparisons, advances and prospects Xin Liang, Lulu Wang, Xiaolong Wu, Xuyong Feng, Qiujie Wu, Yi Sun, Hongfa Xiang, Jiazhao Wang 2022, 73(10): 370-386.  DOI: 10.1016/j.jechem.2022.06.035 Abstract ( 16 )   PDF (13562KB) ( 10 )   Compared with other secondary batteries, lithium-sulfur batteries (LSBs) have unparalleled advantages such as high energy density, low cost, etc. In liquid LSB systems, it is extremely easy to cause severe “shuttle effect” and safety issues. Hence, the development of solid-state LSBs (SSLSBs) has been attracting much more attention. As the most essential part of the SSLSBs, the solid-state electrolyte (SSE) has received significant attention from researchers. In this review, we concentrate on discussing the core of SSLSBs, which is the SSE. Moreover, we also highlight the differences in the properties of the different SSEs, which are polymer-based electrolytes and ceramic-based electrolytes. In addition, the challenges and advances in different types of SSEs are also compared and described systematically. Furthermore, the prospects for new SSE systems and the design of effective SSE structures to achieve high-performance SSLSBs are also discussed. Thus, this review is expected to give readers a comprehensive and systematic understanding of SSEs for SSLSBs.

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In-situ chemical conversion film for stabilizing zinc metal anodes Hao Fu, Qing Wen, Pei-Yao Li, Zhen-yu Wang, Zhen-jiang He, Cheng Yan, Jing Mao, Kehua Dai, Xia-hui Zhang, Jun-chao Zheng 2022, 73(10): 387-393.  DOI: 10.1016/j.jechem.2022.05.033 Abstract ( 9 )   PDF (4968KB) ( 3 )   Zinc metal anodes face several challenges, including the uncontrolled formation of dendrites, hydrogen evolution, and corrosion, which seriously hinder their application in practice. To address the above problems such as dendrite formation and corrosion, we present a simple and applicable immersion method that enables in situ formation of a zinc phytate (PAZ) coating on the surface of commercial Zn flakes via a substitution reaction. This protective coating mitigates corrosion of zinc flakes by the electrolyte, reduces the interfacial impedance, and accelerates the migration kinetics of zinc ions. Besides, this method can preferentially expose the (002) crystal plane with strong atomic bonding, which not only improves the corrosion resistance of the zinc flake, but can also guide the parallel deposition of zinc ions along the (002) crystal plane and reduce the formation of dendrites. Benefiting from the above advantages, the PAZ@Zn||Cu half-cell has shown over 900 cycles with average coulombic efficiency (CE) of 99.81% at 4 mA cm-2. Besides, the PAZ@Zn||PAZ@Zn symmetric cell operate stably for >1000 h at 5 mA cm-2 and >340 h at 10 mA cm-2. Furthermore, we demonstrated that this in situ chemical treatment enables the formation of a robust, well-bound protective coating. This method provides insights for advancing the commercialization of zinc anodes and other metal anodes.

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Electrolyte inhomogeneity induced lithium plating in fast charging lithium-ion batteries Yi Yang, Lei Xu, Shi-Jie Yang, Chong Yan, Jia-Qi Huang 2022, 73(10): 394-399.  DOI: 10.1016/j.jechem.2022.06.001 Abstract ( 25 )   PDF (5960KB) ( 12 )   Fast charging capability of lithium-ion batteries is in urgent need for widespread economic success of electric vehicles. However, the application of the fast charging technology often leads to the inevitable lithium plating on the graphite anode, which is one of the main culprits that endanger battery safety and shorten battery lifespan. The in-depth understanding of the initiation of lithium metal nucleation and the following plating behavior is a key to the development of fast charging cells. Herein, we investigate the overlooked effect of the non-uniform distribution of electrolyte on lithium plating during fast charging. Prior lithium plating occurs on the saturated lithium-graphite compounds in the anode region with sufficient electrolyte since the lithium-ion transport is blocked in the anode region lacking electrolyte. The uniform distribution of electrolyte is crucial for the construction of safe lithium-ion batteries especially in fast charging scenarios.

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Sodiophilic skeleton based on the packing of hard carbon microspheres for stable sodium metal anode without dead sodium Ruoxue Qiu, Si Zhao, Zhijin Ju, Yiyin Huang, Lituo Zheng, Ruqian Lian, Xinyong Tao, Zhensheng Hong 2022, 73(10): 400-406.  DOI: 10.1016/j.jechem.2022.06.033 Abstract ( 14 )   PDF (4878KB) ( 7 )   The propensity of metallic Na dendrites from uneven electrodeposits and the low Coulombic efficiency due to the inevitable existence of “dead sodium” are crucial barriers to realizing the Na metal anode. Herein, we report a multifunctional sodiophilic skeleton based on the packing of hard carbon (HC) microspheres for stable sodium metal electrodeposition without “dead sodium”. Firstly, HC is sodiophilic substrate due to the intrinsic heteroatoms or defects which is a favor for the nucleation of Na. Secondly, silver nanoparticles electroplating on HC (Ag-HC) was adopted to boost the Na diffusion and further regulate the uniform Na metal epitaxial deposition due to well compatibility with AIMD simulation. Finally, the packing of HC microspheres provides the inner space for Na plating. Importantly, it was first found by Cryo-TEM that Na metal deposition in nanoscale is achieved by oriented attachment along [110] direction, leading to the formation of polycrystalline Na metal film on Ag-HC. Such epitaxial deposition can efficiently reduce the formation of “dead sodium” as revealed by chromatography tests, allowing the high Coulombic efficiency and good cycling stability robust kinetics. Finally, HC-Ag||Na3V2(PO4)3 full cell with a low negative/positive ratio of 0.6 is firstly achieved and displays good cycling stability. This finding provides a new practical strategy without pre-plating of Na metals and demonstrates a highly reversible polycrystalline Na metal anode toward a high-energy Na-based battery.

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Enhancing anchoring and catalytic conversion of polysulfides by nitrogen deficient cobalt nitride for advanced lithium-sulfur batteries Min Luo, Yu Bai, Rui Sun, Meixiu Qu, Mengyuan Wang, Zhanfeng Yang, Zhenhua Wang, Wang Sun, Kening Sun 2022, 73(10): 407-415.  DOI: 10.1016/j.jechem.2022.05.029 Abstract ( 10 )   PDF (3783KB) ( 6 )   While lithium-sulfur (Li-S) battery has attracted remarkable attention owing to the high theoretical capacity, its practical application is still hindered by the shuttle and sluggish conversion kinetics of intermediate lithium polysulfides (LiPSs). Defect engineering, which can regulate the electronic structure and in turn influence the surface adsorption and catalytic capability, has been regarded as a feasible strategy to deal with the above challenges. However, few studies on nitrogen vacancies and their mechanisms are reported. Herein, cobalt nitride with nitrogen vacancies grown on multi-walled carbon nanotube (CNT-CoN-VN) is designed and applied as the separator modification material to investigate the enhancing mechanism of nitrogen vacancies on Li-S batteries. The experimental evidence and theoretical calculation indicate that the introduction of nitrogen vacancies into cobalt nitride can enhance the chemical affinity to LiPSs and effectively hamper the shuttle effect. Meanwhile the reduced band gap of the d-band center of Co and p-band center of N for CNT-CoN-VN and the promoted diffusion of Li+ can expedite the solid-liquid and liquid-liquid conversions of sulfur species. Due to these superiorities, the cell with CNT-CoN-VN modified separator delivers a favorable initial capacity of 901 mAh g-1 and a capacity of 660 mAh g-1 can be achieved after 250 cycles at 2 C. This work explores the application of metal nitride with nitrogen vacancies and sheds light on the development of functional separators for high-efficient Li-S batteries.

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Modulated hydrocarbon distribution of gasoline deriving from butene conversion in the presence of syngas Yi Ding, Feng Jiao, Xiulian Pan, Xinhe Bao 2022, 73(10): 416-421.  DOI: 10.1016/j.jechem.2022.06.007 Abstract ( 8 )   PDF (2627KB) ( 3 )   With the expansion of butene production capacity, clean and efficient conversion of mixed butene attracts increasing attention. Herein we report direct co-conversion of butene and syngas to high-quality gasoline enabled by a bifunctional OXZEO catalyst comprising ZnCrOx oxide and ZSM-5 zeolite. A gasoline selectivity of 71.6% at 98.1% butene conversion and 26.2% CO conversion have been obtained under the reaction conditions of 360 °C, 3 MPa and 3000 mL g-1 h-1. The space time yield of gasoline of 0.25 g·g-1·h-1 is achieved. Interestingly, the presence of syngas can effectively facilitate iso-paraffin production while hindering the formation of aromatics. This is attributed to the prohibited hydrogen transfer aromatization process of butene on ZSM-5 in the presence of H2. Furthermore, the formation of isomers of gasoline range hydrocarbons is favored because the active intermediates generated from CO/H2 activation over ZnCrOx oxide could react with butene over ZSM-5 zeolite. Thus, the product distribution among gasoline range hydrocarbons is modulated with reduced heavy aromatics and improved iso-paraffins, which is desirable for application as fuels. This provides an alternative environmentally friendly technology to utilize still increasing mixed butene.

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Regulating dissolution chemistry of nitrates in carbonate electrolyte for high-stable lithium metal batteries Yazhen Zhu, Xiang Li, Yubing Si, Xiuqing Zhang, Pengfei Sang, Yongzhu Fu 2022, 73(10): 422-428.  DOI: 10.1016/j.jechem.2022.06.046 Abstract ( 25 )   PDF (5233KB) ( 12 )   Lithium metal batteries (LMBs) have received increasing attention due to the high energy density. However, the practical application of LMBs is limited due to the incompatibility of ester electrolytes. Transition metal (TM) nitrates have been reported as effective additives in ester electrolyte to improve the stability of lithium anode. Unfortunately, the nitrates are restricted to use due to their poor solubility. We find that the nitrates containing crystal water have high solubility in ester electrolytes. Considering that most TM nitrates contain crystal water and the crystal water can be used as a perfect solubilizer of nitrates, thus, the method is of universality and facile without introducing any solubilizing agent. Herein, In(NO3)3·6H2O is chosen as one typical case with increased solubility up to 0.2 M compared with In(NO3)3 which hardly dissolves in ester electrolyte. The additive promotes the rapid and stable formation of the solid electrolyte interface (SEI), which effectively inhibits the lithium dendrites formation. Moreover, the induced cathode electrolyte interface (CEI) maintains the structural stability of LiNi0.8Co0.1Mn0.1O2 (NCM811). As a result, the electrochemical performance of Li|NCM811 cell is obviously improved. Our study provides a new idea for dissolving nitrates in ester electrolytes and discloses the synergistic function of TM-ions.

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Unveiling the key factor affecting the illumination deterioration and response measures for lead halide perovskite solar cells Feihong Ye, Haibing Wang, Weijun Ke, Chen Tao, Guojia Fang 2022, 73(10): 429-435.  DOI: 10.1016/j.jechem.2022.05.011 Abstract ( 8 )   PDF (5764KB) ( 2 )   So far, it's been widely acknowledged that the PbI2 decomposition under illumination mainly accounts for the degradation of perovskite solar cells (PSCs) under maximum power point (MPP) tracking condition. However, PSCs without excess PbI2 were also reported to deteriorate rapidly under the same condition. Here, we demonstrate that the key to enhance PSCs stability under MPP tracking condition is not to have fascinating surface morphology with effective suppression of nonradiative recombination traps but to prevent the migration of iodine ion (I-) under light illumination. By partially substituting methylammonium chloride (MACl) with methylammonium iodide (MAI) and simutaneouly introducing I2 during the sequential deposition, the iodine vacancies in perovskite films are substantially suppressed, thereby limiting the pathways for I- migration. As a consequence, PSCs with efficiency of 24.28% are fabricated with remarkably enhanced working stability.

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Suppression of partially irreversible phase transition in O′3-Na3Ni2SbO6 cathode for sodium-ion batteries by interlayered structural modulation Jingjie Feng, Jiajie Li, Ni Wen, Siyuan Chen, Jian Wu, Qinghua Fan, Youzhong Dong, Quan Kuang, Yanming Zhao 2022, 73(10): 436-444.  DOI: 10.1016/j.jechem.2022.06.037 Abstract ( 9 )   PDF (10853KB) ( 2 )   As a promising cathode material for sodium ion batteries, honeycomb-ordered layered Na3Ni2SbO6 still suffers from rapid capacity fading because of partially irreversible phase transition. Herein, a substitution of Na+ by Rb+ with a larger ionic radius in honeycomb layered Na3-xRbxNi2SbO6 is proposed to modulate the interlayer structure. The results unveil that biphasic transition reversibility of the intermediate P′3 phase is substantially enhanced, and the structure evolution behavior during the charge/discharge process changes due to the structural modulation, which contributes to a suppression of the unfavorable O1 phase and an alleviation of the lattice distortion. Moreover, Rb substituted samples exhibited an improved Na+ (de)intercalation thermodynamics and kinetics. Attributed to the modifications, the sample with optimized Rb content delivers superior cycle stability and rate capacity, demonstrating a feasible strategy for suppressing irreversible phase transition and developing high-performance honeycomb layered materials for sodium ion batteries.

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Low-cost all-iron flow battery with high performance towards long-duration energy storage Xiaoqi Liu, Tianyu Li, Zhizhang Yuan, Xianfeng Li 2022, 73(10): 445-451.  DOI: 10.1016/j.jechem.2022.06.041 Abstract ( 13 )   PDF (3176KB) ( 10 )   Long duration energy storage (LDES) technologies are vital for wide utilization of renewable energy sources and increasing the penetration of these technologies within energy infrastructures. Herein, we propose a low-cost alkaline all-iron flow battery by coupling ferri/ferro-cyanide redox couple with ferric/ferrous-gluconate complexes redox couple. The designed all-iron flow battery demonstrates a coulombic efficiency of above 99% and an energy efficiency of ∼83% at a current density of 80 mA cm-2, which can continuously run for more than 950 cycles. Most importantly, the battery demonstrates a coulombic efficiency of more than 99.0% and an energy efficiency of ∼83% for a long duration (∼12, 16 and 20 h per cycle) charge/discharge process. Benefiting from the low cost of iron electrolytes, the overall cost of the all-iron flow battery system can be reached as low as $76.11 per kWh based on a 10 h system with a power of 9.9 kW. This work provides a new option for next-generation cost-effective flow batteries for long duration large scale energy storage.

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Free-standing ultrathick LiMn2O4@single-wall carbon nanotubes electrode with high areal capacity Yuntao Guo, Xinhai Li, Zhixing Wang, Jiexi Wang, Huajun Guo, Guochun Yan 2022, 73(10): 452-459.  DOI: 10.1016/j.jechem.2022.05.028 Abstract ( 12 )   PDF (7472KB) ( 2 )   The ever-increasing demands for advanced lithium-ion batteries with high energy density have greatly stimulated the pursuit of thick electrodes with high active material loading. However, it is not feasible to prepare thick electrodes with traditional coating methods due to mechanical instability. Herein, using single-wall carbon nanotubes (SWCNT) as conductive carbon and binder, free-standing LiMn2O4 thick electrodes (F-LMO) with ultrahigh-mass loading up to ∼190 mg cm-2 were prepared by vacuum filtration combined with freeze-drying. The thick electrodes with ∼30 mg cm-2 mass loading achieved a high specific capacity of 106.7 mAh g-1 with a good capacity retention of 94% over 50 cycles at 0.5 C, which was superior to the traditional coating electrodes (∼20 mg cm-2) of 99.3 mAh g-1 with 95% because of the enhanced electronic conductivity originated from SWCNT. In addition, the high active material ratio of 97.5 wt%, near-theoretical reversible capacity, and high mass loading gave ultrathick F-LMO electrodes (600 μm) of ∼190 mg cm-2 with a remarkable areal capacity of 20 mAh cm-2. Moreover, the concentration polarization that occurred in the thick F-LMO electrodes under high current density was discussed via electrochemical stimulation.

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Unraveling the morphological evolution mechanism of solid sulfur species in lithium-sulfur batteries with operando light microscopy Jingqiang Zheng, Chaohong Guan, Huangxu Li, Yangyang Xie, Junxian Hu, Kai Zhang, Bo Hong, Yanqing Lai, Jie Li, Zhian Zhang 2022, 73(10): 460-468.  DOI: 10.1016/j.jechem.2022.04.041 Abstract ( 11 )   PDF (19183KB) ( 1 )   Solid-liquid phase conversion between various sulfur species in lithium-sulfur (Li-S) batteries is a fundamental reaction of the sulfur cathode. Disclosing the morphological evolution of solid sulfur species upon cycling is of great significance to achieving high energy densities. However, an in-depth investigation of the internal reaction is still lacking. In this work, the evolution process of solid sulfur species on carbon substrates is systematically studied by using an operando light microscope combined with in situ electrochemical impedance spectra technology. The observation of phenomena such as bulk solid sulfur species can form and dissolve independently of the conductive substrates and the transformation of supercooled liquid sulfur to crystalline sulfur. Based on the phenomena mentioned above, a possible mechanism was proposed in which the dissolution reaction of solid sulfur species is a spatially free reaction that involves isotropic physical dissolution, diffusion of molecules, and finally the electrochemical reaction. Correspondingly, the formation of solid sulfur species tends to be a form of crystallization in a saturated solution rather than electrodeposition, as is commonly believed. Our findings offer new insights into the reaction of sulfur cathodes and provide new opportunities to design advanced sulfur cathodes for Li-S batteries.

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Engineering the morphology and electronic structure of atomic cobalt-nitrogen-carbon catalyst with highly accessible active sites for enhanced oxygen reduction Zhijun Li, Leipeng Leng, Siqi Ji, Mingyang Zhang, Hongxue Liu, Jincheng Gao, Jiangwei Zhang, J. Hugh Horton, Qian Xu, Junfa Zhu 2022, 73(10): 469-477.  DOI: 10.1016/j.jechem.2022.05.009 Abstract ( 12 )   PDF (8953KB) ( 11 )   The stabilization of non-precious metals as isolated active sites with high loading density over nitrogen-doped carbon materials is essential for realizing the industrial application of single atom catalysts. However, achieving high loading of single cobalt active sites with greatly enhanced oxygen reduction reaction (ORR) activity and stability remains challenging. Here, an efficient approach was described to create a single atom cobalt electrocatalyst (Co SAs/NC) which possesses enhanced mesoporosity and specific surface area that greatly favor the mass transportation and exposure of accessible active sites. The electronic structure of the catalyst by the strong metal-support interaction has been elucidated through experimental characterizations and theoretical calculations. Due to dramatically enhanced mass transport and electron transfer endowed by morphology and electronic structure engineering, Co SAs/NC exhibits remarkable ORR performance with excellent activity (onset and half-wave potentials of 1.04 V (RHE) and 0.90 V (RHE), Tafel slope of 69.8 mV dec-1 and Jk of 18.8 mA cm-2 at 0.85 V) and stability (7 mV activity decay after 10,000 cycles). In addition, the catalyst demonstrates great promise as an alternative to traditional Pt/C catalyst in zinc-air batteries while maintaining high performance in terms of high specific capacity of (796.1 mAh/gZn), power density (175.4 mW/cm2), and long-term cycling stability (140 h). This study presents a facile approach to design SACs with highly accessible active sites for electrochemical transformations.

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Regeneration of single-atom catalysts deactivated under acid oxygen reduction reaction conditions Chang-Xin Zhao, Ding Ren, Juan Wang, Jia-Ning Liu, Cheng Tang, Xiao Chen, Bo-Quan Li, Qiang Zhang 2022, 73(10): 478-484.  DOI: 10.1016/j.jechem.2022.06.005 Abstract ( 10 )   PDF (4679KB) ( 3 )   Single-atom catalysts serve as a promising candidate to realize noble-metal-free electrocatalytic oxygen reduction in acid media. However, their poor stability under working conditions strictly restrains their practical applications. Therefore, regeneration of their electrocatalytic activity is of great significance. Herein, the regeneration of a Fe-N-C single-atom catalyst is demonstrated to be feasible by a facile annealing regeneration strategy. The activity after regeneration recovers to that of the pristine electrocatalyst and surpasses the deactivated electrocatalyst. The regeneration mechanism is identified to be self-etching of the surface carbon layer and consequent exposure of the previously buried single-atom sites. Furthermore, the regeneration strategy is applicable to other single-atom catalysts. This work demonstrates the feasibility of regenerating oxygen reduction electrocatalysts and affords a pioneering approach to deal with rapid deactivation under working conditions.

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Trends and advances in the development of coal fly ash-based materials for application in hydrogen-rich gas production: A review Kang Gao, Maria C. Iliuta 2022, 73(10): 485-512.  DOI: 10.1016/j.jechem.2022.05.016 Abstract ( 12 )   PDF (8830KB) ( 4 )   Coal fly ash (FA), a valuable industrial solid residue generated from coal combustion, is composed of various metal oxides and has a high thermal stability. Given that the coal-based energy will continue to account for a significant portion of global electricity generation in the coming years, the lack of effective management strategies exacerbates the threat of FA wastes to the surrounding environment and human health. For a sustainable development, green and renewable hydrogen economy and CO2 capture efforts provide appealing opportunities to valorize FA as catalysts and/or sorbents due to their appealing physicochemical properties. Hydrogen applications along with carbon neutrality are potential strategies to mitigate climate change crisis, but high processing costs (catalysts/sorbents) are challenging to realize this purpose. In this context, the utilization of FA not only enhances industrial competitiveness (by reducing manufacturing costs), but also provides ecologically friendly approaches to minimizing this solid waste. This state-of-the-art review highlights a wide-ranging outlook on the valorization of FA as catalysts and sorbents for hydrogen-rich gas production via conventional/intensified processes (CO2/H2O reforming, ammonia decomposition, hydride hydrolysis). The fundamental physicochemical characterizations and hazards/utilization of FA, which significantly affect the FA's utilization in various fields, are first introduced. The influence of several factors (like FA types and catalysis/sorption operation conditions) on the activity performance of FA-based materials is then discussed in detail. This critical review aims to open the window to further innovative ideas regarding the application of different FA residues in other catalytic and sorption processes.

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Iron (Fe, Ni, Co)-based transition metal compounds for lithium-sulfur batteries: Mechanism, progress and prospects Junhao Li, Zhangshi Xiong, Yujie Wu, Hao Li, Xinyan Liu, Hongjie Peng, Yuying Zheng, Qiang Zhang, Quanbing Liu 2022, 73(10): 513-532.  DOI: 10.1016/j.jechem.2022.05.034 Abstract ( 8 )   PDF (8130KB) ( 9 )   Lithium-sulfur batteries (LSBs) have a high theoretical capacity, which is considered as one of the most promising high-energy-density secondary batteries due to the double electrons reaction of sulfur. However, the shuttle effects of lithium polysulfides (LiPSs) and sluggish redox kinetics lead to their materials capacity loss and cycle stability deterioration, which restrains LSBs commercialization. Metallic compounds as additions can improve the electrochemical performance of the Li-S system, through the trap of LiPSs and accelerate the conversion of the soluble LiPSs. Among of them, the iron group elements (Fe, Ni, Co)-based compounds are the promising materials for the LSBs, due to their unique outer electronic structure and its tunable properties, low cost, abundant in the earth, environmental benignity, controllable and scalable prepared, and so on. In this review, we have made a summary for iron-based compounds to capture LiPSs according to lithium bond, sulfur bond and magnetic force. The type of iron-based compound including oxides, sulfides, nitrides, phosphides, carbides, and so on, and we have investigated the electrocatalytic mechanism of these materials. Besides, some improvement strategies are proposed, such as the engineering of the special micro/nanostructure, defect concentrations, band structures, and heterostructures. We hope to shed an in-depth light on the rationally design and fabrication of robust, commercial and stable materials for high-performance LSBs.

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Synergistic coupling of amorphous carbon and graphitic domains toward high-rate and long-life K+ storage Hehe Zhang, Wangqin Li, Jianhai Pan, Zhefei Sun, Bensheng Xiao, Weibin Ye, Chengzhi Ke, Haowen Gao, Yong Cheng, Qiaobao Zhang, Ming-Sheng Wang 2022, 73(10): 533-541.  DOI: 10.1016/j.jechem.2022.07.004 Abstract ( 13 )   PDF (8885KB) ( 1 )   Amorphous carbon materials hold great potential for practical use in potassium-ion batteries (PIBs) due to their abundant resources, low cost and high structural stability. However, given the challenge of sluggish potassiation kinetics, the rate performance of amorphous carbon is severely hindered. Herein, amorphous carbon compounded with graphitic domains (HG-CNTs) was proposed as an advanced anode for PIBs. As directly verified by in situ transmission electron microscopy (TEM), the graphitic domains guarantee fast K-ions transport in the carbon composite at a high current density, while the amorphous carbon shells ensure the structural integrity during potassiation, thus boosting its fast and durable K+ storage. As a PIB anode, the HG-CNTs electrode exhibits not only a super-stable long-term cyclability (191.6 mAh g-1 at 1 A g-1 with almost no capacity decay over 3000 cycles), but also an outstanding rate performance (184.5 mAh g-1 at 2 A g-1). Ex situ Raman and TEM results further suggest that the highly reversible structure of HG-CNTs is responsible for its superior electrochemical stability. This work provides helpful insights into the development of carbonaceous electrodes with both high rate capability and long cycle life for PIBs.

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Insights into Ti doping for stabilizing the Na2/3Fe1/3Mn2/3O2 cathode in sodium ion battery Tingting Yang, Yalan Huang, Jian Zhang, He Zhu, Jincan Ren, Tianyi Li, Leighanne C. Gallington, Si Lan, Ligao Yang, Qi Liu 2022, 73(10): 542-548.  DOI: 10.1016/j.jechem.2022.06.016 Abstract ( 6 )   PDF (7937KB) ( 4 )   Iron-and manganese-based layered metal oxides, as cathodes for sodium ion batteries, have received widespread attention because of the low cost and high specific capacity. However, the Jahn-teller effect of Mn3+ ions and the resulted unstable structure usually lead to continuously capacity decay. Herein, Titanium (Ti) has been successfully doped into Na2/3Fe1/3Mn2/3O2 to suppress the Jahn-Teller distortion and improve both cycling and rate performance of sodium ion batteries. In situ high-energy synchrotron X-ray diffraction study shows that Ti-doped compound (Na2/3Fe1/3Mn0.57Ti0.1O2) can maintain the single P2 phase without any phase transition during the whole charging/discharging process. Various electrochemical characterizations are also applied to explore the better kinetics of sodium ions transfer in the Na2/3Fe1/3Mn0.57Ti0.1O2. This work provides a comprehensive insight into the Ti-doping effects on the performance from both structural and electrokinetic perspectives.

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Fluorinated bimetallic nanoparticles decorated carbon nanofibers as highly active and durable oxygen electrocatalyst for fuel cells Yiming Leng, Bolong Yang, Yun Zhao, Zhonghua Xiang 2022, 73(10): 549-555.  DOI: 10.1016/j.jechem.2022.04.026 Abstract ( 5 )   PDF (5514KB) ( 4 )   The low activity and durability are still the critical barriers for non-precious metal electrocatalyst, mainly involving M-N/C (M = Fe, Co, Mn et al), applied in fuel cell. Constructing bimetallic sites has been explored as an effective method to boost the performance of the catalyst for the synergistic effect between metal atoms. However, this synergistic effect is always suppressed in acidic conditions and results in unstable catalytic performance. Here we create novel fluorinated iron (Fe) and cobalt (Co) bimetallic nanoparticles distributed on nitrogen-doped carbon nanofibers (CNFs) for oxygen reduction reaction (ORR). The fluorination strongly increased the charge density of the bimetallic catalyst and resulted in a remarkable catalytic performance with the half-wave potential of 804 mV in 0.1 M HClO4 and 1.6 times power density improvement for the proton exchange membrane fuel cell device. Importantly, the chemical and mechanical robust CNFs support improved the electric conductivity and stability of bimetallic catalysts, which leads to an ultra-stable electrocatalyst. The fuel cell voltage can keep stable even after 110 h, instead of the continuingly decrease in the traditional M-N/C.

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In-situ photoisomerization of azobenzene to inhibit ion-migration for stable high-efficiency perovskite solar cells Xuejiao Zuo, Yiyang He, Hongyu Ji, Yong Li, Xiuying Yang, Binxun Yu, Tao Wang, Zhike Liu, Wenliang Huang, Jing Gou, Ningyi Yuan, Jianning Ding, Shengzhong Frank Liu 2022, 73(10): 556-564.  DOI: 10.1016/j.jechem.2022.06.013 Abstract ( 4 )   PDF (5702KB) ( 2 )

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Fast ion diffusion alloy layer facilitating 3D mesh substrate for dendrite-free zinc-ion hybrid capacitors Huaming Yu, Quanyu Li, Wen Liu, Han Wang, Xuyan Ni, Qiwen Zhao, Weifeng Wei, Xiaobo Ji, Yuejiao Chen, Libao Chen 2022, 73(10): 565-574.  DOI: 10.1016/j.jechem.2022.06.028 Abstract ( 8 )   PDF (12369KB) ( 2 )   Although aqueous zinc ion hybrid capacitors have advantageous integration of batteries and supercapacitors, they still suffer from the inherent problems of dendrite growth and interfacial side reactions on Zn anodes. Herein, a universal fast zinc-ion diffusion layer on a three-dimensional (3D) mesh structure model is demonstrated to effectively improve Zn plating/stripping reversibility. The fast ion diffusion alloy layer accelerates the Zn2+ migration in an orderly manner to homogenize Zn2+ flux and overcomes the defects of the commercial mesh substrate, effectively avoiding dendrite growth and side reactions. Consequently, the proof-of-concept silver-zinc alloy modified stainless steel mesh delivers superb reversibility with the high coulombic efficiency over 99.4% at 4 mA cm-2 after 1600 cycles and excellent reliability of over 830 h at 1 mA cm-2, Its feasibility is also evidenced in commercial zinc ion hybrid capacitors with activated carbon as the cathode. This work enriches the fundamental comprehension of fast zinc-ion diffusion layer combined with a 3D substrate on the Zn deposition and opens a universal approach to design advanced host for Zn electrodes in zinc ion hybrid capacitors.

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Electrolyte design strategies towards long-term Zn metal anode for rechargeable batteries Ming Xu, Jiahang Chen, Yang Zhang, Bareera Raza, Chunyan Lai, Jiulin Wang 2022, 73(10): 575-587.  DOI: 10.1016/j.jechem.2022.06.050 Abstract ( 10 )   PDF (5049KB) ( 8 )   Rechargeable Zinc (Zn) batteries exhibit great potentials as alternative energy storage devices due to their high safety, low cost, and environmental friendliness. However, the long-standing issues of low Coulombic efficiency (CE) and poor cycle stability of Zn anode, derived from dendrite, H2 evolution, and passivation are directly related to their thermodynamic instability in aqueous electrolyte, severely shorten the battery's cycle life. Recently reported electrolyte design strategies, which have made great progress to address Zn metal anode problems, are summarized into two categories, that is, aqueous electrolytes about cation-water interaction controlling and interface adjusting, and novel types of electrolytes towards less water, non-aqueous solvents, even no solvents. The final section shows the brief comparisons, including failure mechanisms of electrolyte exhaustion and short circuit for aqueous and non-aqueous electrolyte based full cells respectively, and possible perspectives for future research.

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Microstructure formation mechanism of catalyst layer and its effect on fuel cell performance: Effect of dispersion medium composition Hong Ren, Xiangchao Meng, Yongli Lin, Zhigang Shao 2022, 73(10): 588-598.  DOI: 10.1016/j.jechem.2022.06.034 Abstract ( 15 )   PDF (10205KB) ( 8 )   The design of the catalyst layer (CL) offers a feasible way to realize the commercialization of proton exchange membrane fuel cells (PEMFCs). An in-depth understanding of catalyst inks is critical to achieving the optimal CL structure and cell performance. In this work, the effects of the solvent evaporation process during ink drying on the formation of the CL microstructure are particularly considered to reveal the structure-property correlations among the catalyst ink, drying process, CL microstructure and fuel cell performance. An increase in the alcohol content of the catalyst ink increases the amount of free ionomers while allowing the ionomer backbone to be more stretched in the dispersion medium. The higher alcohol content contributes to rapid solvent evaporation and thus inhibits the formation of coffee rings; as a result, a more developed ionomer network with a denser pore structure is obtained. Therefore, the alcohol-rich electrode exhibits better proton conduction capability, but higher oxygen transport resistance. For complex fuel cell operating conditions, a catalyst ink formulation with 50 wt% alcohol content is preferred due to its proper ionomer and pore size distribution, providing satisfactory fuel cell performance.

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In-depth understanding of ionic liquid assisted perovskite film formation mechanism for two-step perovskite photovoltaics Fei Wang, Patrick Wai-Keung Fong, Zhiwei Ren, Hai-Lun Xia, Kang Zhou, Kai Wang, Jiajie Zhu, Xiaoxi Huang, Xiao-Yuan Liu, Hao Wang, Yumeng Shi, Haoran Lin, Quanyao Zhu, Gang Li, Hanlin Hu 2022, 73(10): 599-606.  DOI: 10.1016/j.jechem.2022.06.040 Abstract ( 18 )   PDF (6010KB) ( 12 )   Ionic liquids (ILs) have been widely applied in the one-step fabrication of perovskite with noticeable enhancement in the device performance. However, in-depth mechanism of ionic-liquid-assisted perovskite film formation is not well understood for also important two-step perovskite fabrication method, with better control of crystallization behavior. In this work, we introduced ionic liquid methylammonium formate (MAFa) into organic salt to produce perovskite film via a two-step method. Systematic investigations on the influence of MAFa on the perovskite thin film formation mechanism were performed. Ionic liquid is shown to assist lowering the perovskite formation enthalpy upon the density functional theory (DFT) calculation, leading to an accelerated crystallization process evidenced by in-situ UV-Vis absorption measurement. A gradient up-down distribution of ionic liquid has been confirmed by time-of-flight SIMS. Importantly, besides the surface passivation, we found the HCOO- can diffuse into the perovskite crystals to fill up the halide vacancies, resulting in significant reduction of trap states. Uniform perovskite films with significantly larger grains and less defect density were prepared with the help of MAFa IL, and the corresponding device efficiency over 23% was obtained by two-step process with remarkably improved stability. This research work provides an efficient strategy to tune the morphology and opto-electronic properties of perovskite materials via ionic-liquid-assisted two-step fabrication method, which is beneficial for upscaling and application of perovskite photovoltaics.

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Selective production of acetol or methyl lactate from cellulose over RuSn catalysts Dawang Chu, Zhicheng Luo, Chen Zhao 2022, 73(10): 607-614.  DOI: 10.1016/j.jechem.2022.06.043 Abstract ( 7 )   PDF (5255KB) ( 2 )   Designing a catalytic system that could convert cellulose to switchable C3 alcohols or esters with controllable selectivity is highly desired to meet the rapidly changing market demand. Herein, we develop RuSn catalysts with the altering Sn loadings that can achieve acetol formation from cellulose hydrogenation at 240 °C in presence of H2 or yield methyl lactate production from cellulose conversion in methanol and water mixture at 200 °C in presence of N2. The increased Sn contents from 3% to 6% lead to form different surface sites from Ru3Sn7, Ru, and SnOx to Ru3Sn7 and SnOx. The integrated Ru3Sn7, Ru, and SnOx species on 1.5%Ru-3%Sn/SiO2 catalyze isomerization, retro-aldol condensation, and hydrogenation individual steps with coordinated reaction rates, resulting in the acetol formation with a high yield of 53.7C%. Furthermore, the optimum combination of Ru3Sn7 and SnOx on 1.5%Ru-6%Sn/SiO2 contributes to the isomerization, retro-aldol condensation, dehydration, and 1,2-hydride shift, giving rise to the preferential production of methyl lactate at a 25.1C% yield. These results illustrate the feasibility of controlling the selective conversion of cellulose to C3 acetol or methyl lactate by devising a tunable catalytic system, which guides the rational design of catalysts for the selective conversion of cellulose.

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Recent advances in Pb-Sn mixed perovskite solar cells Yanyu Deng, Guanhua Ren, Danao Han, Wenbin Han, Zhuowei Li, Chunyu Liu, Wenbin Guo 2022, 73(10): 615-638.  DOI: 10.1016/j.jechem.2022.07.003 Abstract ( 30 )   PDF (21998KB) ( 13 )   Organic-inorganic hybrid lead-tin perovskite solar cells (Pb-Sn PSCs) have attracted much attention because of their advantages of low toxicity, variable bandgap, and feasibility for all-perovskite tandem solar cells, and the current power conversion efficiency (PCE) has exceeded 23%. However, due to the rambunctious crystallization process, easily oxidized Sn(Ⅱ) and inadequate energy level arrangement, there are many defects in perovskite films resulting in serious carrier recombination, which makes PCE still lag Pb-based PSCs. The quality of perovskite films is an important factor affecting the overall device performance. The selection and optimization of transport layers not only determines the interface energy level arrangement but also affects the carrier transport. In this paper, the research progress in improving performance of Pb-Sn PSCs in recent years is reviewed from aspects of perovskite layer and transport layers. The profound understanding of different promotion methods is summarized as well. These results have certain guiding significance for the future development and commercial application of Pb-Sn PSCs.

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X-ray ptychographic tomography reveals buried 3D structural defects in metal halide perovskites Yalan Zhang, Mingwei Hao, Hua Zhou, Junjing Deng, Yuanyuan Zhou 2022, 73(10): 639-642.  DOI: 10.1016/j.jechem.2022.06.025 Abstract ( 21 )   PDF (1426KB) ( 6 )

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The future challenges in molecular water oxidation catalysts Tianqi Liu, Licheng Sun 2022, 73(10): 643-645.  DOI: 10.1016/j.jechem.2022.07.001 Abstract ( 9 )   PDF (648KB) ( 3 )