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2020, Vol. 42, No. 3　Online: 2020-03-15

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Improving metallic lithium anode with NaPF6 additive in LiPF6-carbonate electrolyte Jiarui Liu, Yingli Wang, Fangming Liu, Fangyi Cheng, Jun Chen 2020, 42(3): 1-4.  DOI: 10.1016/j.jechem.2019.05.017 摘要 ( 6 )

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Molten salt-assisted synthesis of bulk CoOOH as a water oxidation catalyst Sanzhao Song, Hongliang Bao, Xiao Lin, Xian-Long Du, Jing Zhou, Linjuan Zhang, Ning Chen, Jun Hu, Jian-Qiang Wang 2020, 42(3): 5-10.  DOI: 10.1016/j.jechem.2019.05.021 摘要 ( 13 )   Different sizes of layered CoOOH were synthesized by the molten-salt-assisted method at different temperatures. X-ray diffraction and scanning electron microscope studies reveal that CoOOH grew at (003) with increasing temperature, and its size can reach dozens of microns. X-ray absorption near edge structure and XPS studies demonstrate that the Co valence state of CoOOH-750 is trivalent, and X-ray Absorption Fine Structure shows that it had a higher symmetry and lower disorder degree, indicating that CoOOH-750 has higher crystallinity and Co3+. The results of electrochemical tests show that CoOOH-750 exhibited the best oxygen-evolution-reaction (OER) catalytic activity.

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A study on hydrogen uptake and release of a eutectic mixture of biphenyl and diphenyl ether Munjeong Jang, Byeong Soo Shin, Young Suk Jo, Jeong Won Kang, Sang Kyu Kwak, Chang Won Yoon, Hyangsoo Jeong 2020, 42(3): 11-16.  DOI: 10.1016/j.jechem.2019.05.024 摘要 ( 10 )   Hydrogen storage in Liquid Organic Hydrogen Carrier (LOHC) systems is appealing for the safe storage and distribution of excess renewable energy via existing gasoline infrastructures to end-users. We present the eutectic mixture of biphenyl and diphenyl ether of its first use as a LOHC material. The material is hydrogenated with 99% selectivity without the cleavage of C-O bond, with commercial heterogeneous catalysts, which is confirmed by nuclear magnetic spectroscopy and gas chromatography-mass spectrometry. Equilibrium concentration, dehydrogenation enthalpy, and thermo-neutral temperature are calculated using a density functional theory. The results indicate that O-atom-containing material exhibits more favorable dehydrogenation thermodynamics than that of the hydrocarbon analogue. The H2-rich material contains 6.8 wt% of gravimetric hydrogen storage capacity. A preliminary study of catalytic dehydrogenation on a continuous reactor is presented to demonstrate a reversibility of this material.

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All-carbon positive electrodes for stable aluminium batteries Zhili Zhou, Na Li, Peng Wang, Wei-Li Song, Shuqiang Jiao, Haosen Chen, Daining Fang 2020, 42(3): 17-26.  DOI: 10.1016/j.jechem.2019.03.027 摘要 ( 13 )   For addressing the critical problems in current collectors in the aluminium batteries, a variety of carbonbased current collectors, including carbon fiber textiles and three-dimensional (3D) biomass-derivative carbon (BDC) networks, are employed for serving as lightweight non-metal current collectors. The results indicate that all the carbon-based current collectors have electrochemical stability in the acidic electrolyte environments. In the assembled aluminium batteries with all-carbon positive electrodes, thermal annealing process on the carbon-based current collectors has substantially promoted the entire electrochemical energy storage performance. Additionally, both the structure configuration and chemical components of the current collectors have also great impact on the rate capability and cycling stability, implying that the 3D BDC networks are more favorable to offer promoted energy storage capability. Implication of the results from suggests that the carbon-based current collectors and all-carbon positive electrodes are able to deliver more advantages in energy storage behaviors in comparison with the traditional positive electrodes with metal Mo current collectors. Such novel strategy promises a new route for fabricating highperformance positive electrodes for stable advanced aluminium batteries.

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Grafting polymeric sulfur onto carbon nanotubes as highly-active cathode for lithium-sulfur batteries Junfeng Wu, Siyu Ding, Shihai Ye, Chao Lai 2020, 42(3): 27-33.  DOI: 10.1016/j.jechem.2019.05.020 摘要 ( 12 )   Lithium-sulfur (Li-S) batteries are being explored as promising advanced energy storage systems due to their ultra-high energy density. However, fast capacity fading and low coulombic efficiency, resulting from the dissolution of polysulfides, remain a serious challenge. Compared to weak physical adsorptions or barriers, chemical confinement based on strong chemical interaction is a more effective approach to address the shuttle issue. Herein, we devise a novel polymeric sulfur/carbon nanotube composite for Li-S battery, for which 2, 5-dithiobiurea is chosen as the stabilizer of long-chain sulfur. This offers chemical bonds which bridge the polymeric sulfur and carbon nanotubes. The obtained composite can deliver an ultra-high reversible capacity of 1076.2 mAh g-1 (based on the entire composite) at the rate of 0.1 C with an exceptional initial Coulombic efficiency of 96.2%, as well as remarkable cycle performance. This performance is mainly attributed to the reaction reversibility of the obtained polymeric sulfur-based composite during the discharge/charge process. This was confirmed by density functional theory calculations for the first time.

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Bio-templated formation of defect-abundant VS2 as a bifunctional material toward high-performance hydrogen evolution reactions and lithium-sulfur batteries Tianqi Guo, Yingze Song, Zhongti Sun, Yuhan Wu, Yu Xia, Yayun Li, Jianhui Sun, Kai Jiang, Shixue Dou, Jingyu Sun 2020, 42(3): 34-42.  DOI: 10.1016/j.jechem.2019.06.007 摘要 ( 13 )   Transition metal chalcogenides have nowadays garnered burgeoning interest owing to their fascinating electronic and catalytic properties, thus possessing great implications for energy conversion and storage applications. In this regard, their controllable synthesis in a large scale at low cost has readily become a focus of research. Herein we report diatomite-template generic and scalable production of VS2 and other transition metal sulfides targeting emerging energy conversion and storage applications. The conformal growth of VS2 over diatomite template would endow them with defect-abundant features. Throughout detailed experimental investigation in combination with theoretical simulation, we reveal that the enriched active sites/sulfur vacancies of thus-derived VS2 architectures would pose positive impacts on the catalytic performance such in electrocatalytic hydrogen evolution reactions. We further show that the favorable electrical conductivity and highly exposed sites of VS2 hold promise for serving as sulfur host in the realm of Li-S batteries. Our work offers new insights into the templated and customized synthesis of defect-rich sulfides in a scalable fashion to benefit multifunctional energy applications.

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Selective extraction of titanium from Ti-bearing slag via the enhanced depolarization effect of liquid copper cathode Zhenghao Pu, Handong Jiao, Zhishan Mi, Mingyong Wang, Shuqiang Jiao 2020, 42(3): 43-48.  DOI: 10.1016/j.jechem.2019.06.004 摘要 ( 13 )   Ti-bearing slag (TiO2>20 wt%) is a valuable titanium secondary resource. The extraction of titanium from the slag is difficult due to the complex composition and structure. Although molten oxide electrolysis is considered as a promising method, silicon will be preferentially electroreduced compared to titanium due to low theoretical decomposition voltage. In this work, a liquid copper cathode is used to selectively extract titanium from molten Al2O3-MgO-CaO-TiO2-SiO2 electrolyte. It is found that comparing to silicon, titanium can be preferentially reduced by one-step electron transfer due to the enhanced depolarization effect on a liquid copper cathode. So, Ti-Cu alloys are firstly obtained from molten Ti-bearing slag, and then Ti-Si alloys are co-electrodeposited in the molten oxide electrolyte with low TiO2 content. It may be ascribed to the larger binding force between titanium and copper than that between silicon and copper. It provides an effective strategy for the separation of titanium from of Ti-bearing slag.

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Investigation of polysulfone film on high-performance anode with stabilized electrolyte/electrode interface for lithium batteries Yuyan Ma, Chen Dong, Qiuli Yang, Yuxin Yin, Xiaoping Bai, Shuying Zhen, Cheng Fan, Kening Sun 2020, 42(3): 49-55.  DOI: 10.1016/j.jechem.2019.06.008 摘要 ( 10 )   Lithium metal has been considered to be the most promising anode material for the new generation of energy-storage system. However, challenges still stand in protecting lithium metal from spontaneous reactions with electrolytes and preventing the dendritic propagation, both of which would lead to undesirable decrease in Coulombic efficiency. Polysulfone (PSf) membrane with high rigidity and free-volume cavities of approximately 0.3 nm was employed to provide a stable interface on the surface of anodic electrode. The isotropic channels were constructed by the interconnected and uniformly distributed free volumes in the polymer matrix, and were expected to be swelled by solvent molecules and anions of lithium salt and to allow Li+ ions to pass through onto the electrode surface. As a result, dendrite-free morphology of deposited lithium was observed. The stabilized interface arose from the PSf film was verified by the promoted performances of Cu|Li cells and steady voltage polarization of Li|Li cells. The full cell with PSf coated anode exhibited excellent cyclability (85% capacity retention rate over 400 cycles at 1 C) and an outstanding rate capability (117 mAh g-1 at 5 C). The beneficial performances were further verified by the EIS results. This work provides a new strategic idea to settle the dendritic problems of Li metal anodes.

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Synthesis of mechanically robust porous carbon monoliths for CO2 adsorption and separation Jie Du, Wen-Cui Li, Zhan-Xin Ren, Li-Ping Guo, An-Hui Lu 2020, 42(3): 56-61.  DOI: 10.1016/j.jechem.2019.06.006 摘要 ( 7 )   Porous carbon materials with developed porosity, high surface area and good thermal- and chemicalresistance are advantageous for gas adsorption and separation. However, most carbon adsorbents are in powder form which exhibit high pressure drop when deployed in practical separation bed. While monolithic carbons have largely addressed the pulverization problem and preserved kinetics and usually suffer from abrasion during multiple adsorption-desorption cycles. Herein, we proposed the designed synthesis of mechanically robust carbon monoliths with hierarchical pores, solid nitrogen-containing framework. The synthesis started with the polymerization of resorcinol and formaldehyde under weakly acidic conditions generated from cyanuric acid, and then an appropriate amount of hexamethylenetetramine (HMTA) was added as a crosslinker to prompt the formation of three dimensional frameworks. After carbonization process, the as-obtained porous carbon monoliths have a high radial compressive strength of 886 N/cm as well as a BET specific surface area of up to 683 m2/g. At approximately 1 bar, the CO2 equilibrium capacities of the monoliths are in the range of 3.1-4.0 mmol/g at 273 K and of 2.3-3.0 mmol/g at 298 K, exhibiting high selectivity for the capture of CO2 over N2 from a stream which consists of 16.7% (v%) CO2 in N2. Meanwhile, they undergo a facile CO2 release in an argon stream at 298 K, indicating a good regeneration capacity. After cycle testing, sieving and regeneration, the adsorbent has no mass loss, compared to that of its fresh counterpart.

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Exploring high-voltage fluorinated carbonate electrolytes for LiNi0.5Mn1.5O4 cathode in Li-ion batteries Xi Zheng, Ying Liao, Zhongru Zhang, Jianping Zhu, Fucheng Ren, Huajin He, Yuxuan Xiang, Yezhen Zheng, Y. Yang 2020, 42(3): 62-70.  DOI: 10.1016/j.jechem.2019.05.023 摘要 ( 36 )   Ethyl-(2,2,2-trifluoroethyl) carbonate (ETFEC) is investigated as a solvent component in high-voltage electrolytes for LiNi0.5Mn1.5O4 (LNMO). Our results show that the self-discharge behavior and the high temperature cycle performance can be significantly improved by the addition of 10% ETFEC into the normal carbonate electrolytes, e.g., the capacity retention improved from 65.3% to 77.1% after 200 cycles at 60℃. The main reason can be ascribed to the high stability of ETFEC which prevents large oxidation of the electrolyte on the cathode surface. In addition, we also explore the feasibility of electrolytes using single fluoriated-solvents with and without additives. Our results show that the cycle performance of LNMO material can be greatly improved in 1 M LiPF6 + pure ETFEC-solvent system with 2 wt% ethylene carbonate (EC) or ethylene sulfate (DTD). The capacity retention of the LNMO materials is 93% after 300 cycles, even better than that of carbonate-based electrolytes. It is shown that the additives are oxidized on the surface of LNMO particles and contribute to the formation of cathode/electrolyte interphase (CEI) films. This composite CEI film plays a crucial role in suppressing the serious decomposition of the electrolyte at high voltage.

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Self-supported Ni2P nanosheets on low-cost three-dimensional Fe foam as a novel electrocatalyst for efficient water oxidation Mengrong Zhang, Taotao Wang, Hongyun Cao, Shengsheng Cui, Pingwu Du 2020, 42(3): 71-76.  DOI: 10.1016/j.jechem.2019.06.010 摘要 ( 5 )   Electrochemical water splitting into hydrogen and oxygen is a promising strategy for future renewable energy conversion devices. The oxygen evolution reaction (OER) is considered as the bottleneck reaction in an overall water splitting system because it involves 4e- and 4H+ transfer processes. Currently, it is highly desirable to explore low-cost alternative catalysts for OER at ambient conditions. Herein, we report for the first time that nickel phosphide (Ni2P) nanosheets can be facilely grown on Fe foam (FF) as an efficient electrocatalyst for OER with excellent durability and catalytic activity under alkaline conditions. To reach a current density of 10 mA/cm2, the Ni2P-FF catalyst required a low overpotential of only 198 mV for OER. The catalyst's high OER activity and durability were well maintained at a high current density. The required overpotentials were only 267 and 313 mV to achieve the current densities of 100 and 300 mA/cm2, respectively. The combination of low-cost Fe foam with Ni2P provides a promising low-cost catalyst for large-scale application of electrocatalytic water splitting.

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Novel two-step CdS deposition strategy to improve the performance of Cu2ZnSn(S,Se)4 solar cell Lifang Teng, Junye Tong, Gang Wang, Lingling Wang, Liping Chen, Shaotong Wang, Yinglin Wang, Daocheng Pan, Xintong Zhang, Yichun Liu 2020, 42(3): 77-82.  DOI: 10.1016/j.jechem.2019.06.011 摘要 ( 12 )   Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cells have drawn worldwide attention for their promising photovoltaics performance and earth-abundant element composition, yet the record efficiency of this type of device is still far lower than its theoretical conversion efficiency. Undesirable band alignment and severe non-radiative recombination at CZTSSe/CdS heterojunction interfaces are the major causes limiting the current/voltage output and overall device performance. Herein, we propose a novel two-step CdS deposition strategy to improve the quality of CZTSSe/CdS heterojunction interface and thereby improve the performance of CZTSSe solar cell. The two-step strategy includes firstly pre-deposits CdS thin layer on CZTSSe absorber layer by chemical bath deposition (CBD), followed with a mild heat treatment to facilitate element inter-diffusion, and secondly deposits an appropriate thickness of CdS layer by CBD to cover the whole surface of pre-deposited CdS and CZTSSe layers. The solar energy conversion efficiency of CZTSSe solar cells with two-step deposited CdS layer approaches to 8.76% (with an active area of about 0.19 cm2), which shows an encouraging improvement of over 87.98% or 30.16% compared to the devices with traditional CBD-deposited CdS layer without and with the mild annealing process, respectively. The performance enhancement by the two-step CdS deposition is attributed to the formation of more favorable band alignment at CZTSSe/CdS interface as well as the effective decrease in interfacial recombination paths on the basis of material and device characterizations. The two-step CdS deposition strategy is simple but effective, and should have large room to improve the quality of CZTSSe/CdS heterojunction interface and further lift up the conversion efficiency of CZTSSe solar cells.

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PIM-1 as an artificial solid electrolyte interphase for stable lithium metal anode in high-performance batteries Qiuli Yang, Wenli Li, Chen Dong, Yuyan Ma, Yuxin Yin, Qibing Wu, Zhitao Xu, Wei Ma, Cheng Fan, Kening Sun 2020, 42(3): 83-90.  DOI: 10.1016/j.jechem.2019.06.012 摘要 ( 30 )   Lithium metal anode is a promising electrode with high theoretical specific capacity and low electrode potential. However, its unstable interface and low Coulombic efficiency, resulting from the dendritic growth of lithium, limits its commercial application. PIM-1 (PIM:polymer of intrinsic microporosity), which is a polymer with abundant micropores, exhibits high rigidity and flexibility with contorted spirocenters in the backbone, and is an ideal candidate for artificial solid electrolyte interphases (SEI). In this work, a PIM-1 membrane was synthesized and fabricated as a protective membrane on the surface of an electrode to facilitate the uniform flux of Li ions and act as a stable interface for the lithium plating/stripping process. Nodule-like lithium with rounded edges was observed under the PIM-1 membrane. The Li@PIM-1 electrode delivered a high average Coulombic efficiency (99.7%), excellent cyclability (80% capacity retention rate after 600 cycles at 1 C), and superior rate capability (125.3 mAh g-1 at 10 C). Electrochemical impedance spectrum (EIS) showed that the PIM-1 membrane could lower the diffusion rate of Li+ significantly and change the rate-determining step from charge transfer to Li+ diffusion. Thus, the PIM-1 membrane is proven to act as an artificial SEI to facilitate uniform and stable deposition of lithium, in favor of obtaining a compact and dense Li-plating pattern. This work extends the application of PIMs in the field of lithium batteries and provides ideas for the construction of artificial SEI.

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Recent advances in graphene based materials as anode materials in sodium-ion batteries Kimal Chandula Wasalathilake, Henan Li, Li Xu, Cheng Yan 2020, 42(3): 91-107.  DOI: 10.1016/j.jechem.2019.06.016 摘要 ( 29 )   Sodium-ion batteries (SIBs) have emerged as a promising alternative to Lithium-ion batteries (LIBs) for energy storage applications, due to abundant sodium resources, low cost, and similar electrochemical performance. However, the large radius of Na+ and high molar mass compared to Li+, result in large volume strain during charge/discharge and low reversible capacity and poor cycling stability. Due to exceptional physical and chemical properties, graphene has attracted increasing attention as a potential anode material for SIBs. When integrated with other nanomaterials in electrodes, graphene can improve the electrical conductivity, accommodate the large volume change and enhance reaction kinetics. This paper provides a systematic review of recent progress in the application of graphene based anodes for SIBs, with a focus on preparation, structural configuration, Na+ storage mechanism and electrochemical performance. Additionally, some challenges and future perspectives are provided to improve the sodium storage performance of graphene based electrodes.

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Free-standing ternary metallic sulphides/Ni/C-nanofiber anodes for high-performance lithium-ion capacitors Ting Xing, Yinghui Ouyang, Liping Zheng, Xianyou Wang, Hong Liu, Manfang Chen, Ruizhi Yu, Xingyan Wang, Chun Wu 2020, 42(3): 108-115.  DOI: 10.1016/j.jechem.2019.06.002 摘要 ( 12 )   As a promising energy-storage device, the hybrid lithium-ion capacitor coupling with both a large energy density battery-type anode and a high power density capacitor-type cathode is attracting great attention. For the sake of improving the energy density of hybrid lithium-ion capacitor, the free-standing anodes with good electrochemical performance are essential. Herein, we design an effective electrospinning strategy to prepare free-standing MnS/Co4S3/Ni3S2/Ni/C-nanofibers (TMSs/Ni/C-NFs) film and firstly use it as a binder-free anode for hybrid lithium-ion capacitor. We find that the carbon nanofibers can availably prevent MnS/Co4S3/Ni3S2/Ni nanoparticles from aggregation as well as significantly improve the electrochemical performance. Therefore, the binder-free TMSs/Ni/C-NFs membrane displays an ultrahigh reversible capacity of 1246.9 mAh g-1 at 100 mA g-1, excellent rate capability (398 mAh g-1 at 2000 mA g-1), and long-term cyclic endurance. Besides, we further assemble the hybrid lithium-ion capacitor, which exhibits a high energy density of 182.0 Wh kg-1 at 121.1 W kg-1 (19.0 Wh kg-1 at 3512.5 W kg-1) and remarkable cycle life.

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Ultra-lightweight Ti3C2Tx MXene modified separator for Li-S batteries: Thickness regulation enabled polysulfide inhibition and lithium ion transportation Nuo Li, Ying Xie, Shuting Peng, Xiang Xiong, Kai Han 2020, 42(3): 116-125.  DOI: 10.1016/j.jechem.2019.06.014 摘要 ( 17 )   The practical application of lithium-sulfur (Li-S) batteries is limited by the easy dissolution of polysulfides in the electrolyte, resulting in the lithium polysulfide (LPS) shuttle effect. Several two-dimensional (2D) materials with abundant active binding sites and high surface-to-volume ratios have been developed to prepare functional separators that suppress the diffusion of polysulfides. However, the influence of modified layer thickness on Li+ transport has not been considered. Herein, we synthesized individual and multilayered 2D Ti3C2Tx MXene nanosheets and used them to fabricate a series of Ti3C2Tx-PP modified separators. The separators had mass loadings ranging from 0.16 to 0.016 mg cm-2, which is the lowest value reported for 2D materials to the best of our knowledge. The corresponding reductions in thickness ranged from 1.2 μm to 100 nm. LPS shuttling was effectively suppressed, even at the lowest mass loading of 0.016 mg cm-2. Suppression was due to the strong interaction between LPS intermediates and Ti atoms and hydroxyl functional groups on the separator surface. The lithium-ion diffusion coefficient increased with the reduction of Ti3C2Tx layers on the separator. Superior cycling stability and rate performance were attained when the separator with a Ti3C2Tx-PP mass loading of 0.016 mg cm-2 was incorporated into a Li-S battery. Carbon nanotubes (CNTs) were introduced into the separators to further improve the electrical and Li+ ionic conductivity in the cross-plane direction of the 2D Ti3C2Tx layers. With the ultralightweight Ti3C2Tx/CNTs modified PP separator, the cell maintained a capacity of 640 mAh g-1 after 200 cycles at 1 C with a capacity decay of only 0.079% per cycle.

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A new insight into the stability of nanofiber electrodes used in proton exchange membrane fuel cells Yanyan Gao, Ming Hou, Liang He, Manman Qi, Haiping Chen, Shaojing Hong, Yongyi Jiang, Zhigang Shao, Baolian Yi 2020, 42(3): 126-132.  DOI: 10.1016/j.jechem.2019.06.017 摘要 ( 13 )   The nanofiber electrodes have been considered as promising candidates for commercial proton exchange membrane fuel cells due to their high catalyst utilization and enhanced mass transport efficiency. However, for the first time our research determined that the nanofiber electrodes were restricted by the poor chemical stability of the polymer carriers. To gain further insight into the durability of nanofiber electrodes, both cyclic voltammetry aging tests and Fenton's tests were conducted. Similar to previous reports, our research demonstrated that nanofiber electrodes showed remarkable stability in the cyclic voltammetry aging process. However, Fenton's tests indicated that nanofibers in the electrodes would decompose easily while being attacked by reactive oxygen species such as HO· or HOO·, which greatly limits their practicability and reliability. The different performances under the two tests also demonstrated that the cyclic voltammetry aging protocols, which have been applied extensively, cannot well mirror the real operating conditions of fuel cells.

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Crystal structure evolution of complex metal aluminum hydrides upon hydrogen release Claudia Weidenthaler 2020, 42(3): 133-143.  DOI: 10.1016/j.jechem.2019.05.026 摘要 ( 8 )   Complex aluminum hydrides have been widely studied as potential hydrogen storage materials but also, for some time now, for electrochemical applications. This review summarizes the crystal structures of alkali and alkaline earth aluminum hydrides and correlates structure properties with physical and chemical properties of the hydride compounds. The crystal structures of the alkali metal aluminum hydrides change significantly during the stepwise dehydrogenation. The general pathway follows a transformation of structures built of isolated[AlH4]- tetrahedra to structures built of isolated[AlH6]3- octahedra. The crystal structure relations in the group of alkaline earth metal aluminum hydrides are much more complicated than those of the alkali metal aluminum hydrides. The structures of the alkaline earth metal aluminum hydrides consist of isolated tetrahedra but the intermediate structures exhibit chains of cornershared octahedra. The coordination numbers within the alkali metal group increase with cation sizes which goes along with an increase of the decomposition temperatures of the primary hydrides. Alkaline earth metal hydrides have higher coordination numbers but decompose at slightly lower temperatures than their alkali metal counterparts. The decomposition pathways of alkaline metal aluminum hydrides have not been studied in all cases and require future research.

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Recent advances in chemical adsorption and catalytic conversion materials for Li-S batteries Xiaodong Hong, Rui Wang, Yue Liu, Jiawei Fu, Ji Liang, Shixue Dou 2020, 42(3): 144-168.  DOI: 10.1016/j.jechem.2019.07.001 摘要 ( 27 )   Owing to their low cost, high energy densities, and superior performance compared with that of Li-ion batteries, Li-S batteries have been recognized as very promising next-generation batteries. However, the commercialization of Li-S batteries has been hindered by the insulation of sulfur, significant volume expansion, shuttling of dissolved lithium polysulfides (LiPSs), and more importantly, sluggish conversion of polysulfide intermediates. To overcome these problems, a state-of-the-art strategy is to use sulfur host materials that feature chemical adsorption and electrocatalytic capabilities for LiPS species. In this review, we comprehensively illustrate the latest progress on the rational design and controllable fabrication of materials with chemical adsorbing and binding capabilities for LiPSs and electrocatalytic activities that allow them to accelerate the conversion of LiPSs for Li-S batteries. Moreover, the current essential challenges encountered when designing these materials are summarized, and possible solutions are proposed. We hope that this review could provide some strategies and theoretical guidance for developing novel chemical anchoring and electrocatalytic materials for high-performance Li-S batteries.

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A new non-fullerene acceptor based on the heptacyclic benzotriazole unit for efficient organic solar cells Mei Luo, Liuyang Zhou, Jun Yuan, Can Zhu, Fangfang Cai, Jiefeng Hai, Yingping Zou 2020, 42(3): 169-173.  DOI: 10.1016/j.jechem.2019.07.002 摘要 ( 55 )

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Concrete-like high sulfur content cathodes with enhanced electrochemical performance for lithium-sulfur batteries Bolan Gan, Kaikai Tang, Yali Chen, Dandan Wang, Na Wang, Wenxian Li, Yong Wang, Hao Liu, Guoxiu Wang 2020, 42(3): 174-179.  DOI: 10.1016/j.jechem.2019.06.003 摘要 ( 18 )   Nowadays, lithium-sulfur batteries have attracted numerous attention due to their high specific capacity, high energy density, low cost and environmental benignancy. However, there are some critical challenges to be overcome such as low electronic conductivity and capacity fading caused by shuttle effect. Many attempts have been conducted to improve the electrochemical performance by designing effective sulfur hosts. In this paper, we synthesize a concrete-like sulfur/carbon cathode with high sulfur content (84%) by using 3D macroporous hosts with high pore volume. Sophisticated strategies of using polarized carbon framework and polymer coating are applied to synergistically control the dissolution of polysulfides so that the capacity retention and high rate performance can be remarkably enhanced. As a result, the composite exhibits a specific discharge capacity of 820 mAh g-1 at a discharge current of 800 mA g-1 (approximate to 0.5 C) after 100 cycles, calculated on the integrated mass of composite, which is superior to most report results.

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Dual-ion hybrid supercapacitor: Integration of Li-ion hybrid supercapacitor and dual-ion battery realized by porous graphitic carbon Changzhen Zhan, Xiaojie Zeng, Xiaolong Ren, Yang Shen, Ruitao Lv, Feiyu Kang, Zheng-Hong Huang 2020, 42(3): 180-184.  DOI: 10.1016/j.jechem.2019.06.009 摘要 ( 22 )   Lithium-ion hybrid supercapacitors (Li-HSCs) and dual-ion batteries (DIBs) are two types of energy storage devices that have attracted extensive research interest in recent years. Li-HSCs and DIBs have similarities in device structure, tendency for ion migration, and energy storage mechanisms at the negative electrode. However, these devices have differences in energy storage mechanisms and working potentials at the positive electrode. Here, we first realize the integration of a Li-HSC and a DIB to form a dual-ion hybrid supercapacitor (DIHSC), by employing mesocarbon microbead (MCMB)-based porous graphitic carbon (PGC) with a partially graphitized structure and porous structure as a positive electrode material. The MCMB-PGC-based DIHSC exhibits a novel dual-ion battery-capacitor hybrid mechanism:it exhibits excellent electronic double-layer capacitor (EDLC) behavior like a Li-HSC in the low-middle wide potential range and anion intercalation/de-intercalation behavior like a DIB in the high-potential range. Two types of mechanisms are observed in the electrochemical characterization process, and the energy density of the new DIHSC is significantly increased.

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Catalytic performance of zinc-supported copper and nickel catalysts in the glycerol hydrogenolysis R. J. Chimentão, B. C. Miranda, D. Ruiz, F. Gispert-Guirado, F. Medina, J. Llorca, J. B. O. Santos 2020, 42(3): 185-194.  DOI: 10.1016/j.jechem.2019.07.003 摘要 ( 10 )   Gas-phase catalytic conversion of glycerol to value added chemicals was investigated over zinc-supported copper and nickel catalysts. The addition of aluminum in the support was also investigated in glycerol conversion and the results indicate an increase in the acidity and adsorption capacity for both copper and nickel catalysts. HRTEM and XRD analysis revealed NiZn alloy formation in the Ni/ZnO catalyst. The XRD patterns of the prepared ZnAl mixed oxide catalysts show the presence of Gahanite phase (ZnAl2O4). In addition, H2 chemisorption and TPR results suggest a strong metal-support interactions (SMSI) effect between Ni and ZnO particles. Bare supports ZnO and ZnAl (Zn/Al=0.5) were investigated in the glycerol conversion and they did not present activity. Copper supported on ZnO and ZnAl mixed oxide (Zn/Al=0.5) was active towards hydroxyacetone formation. Nickel was active in the hydrogenolysis of glycerol both for C-C and C-O bonds cleavage of glycerol producing CH4. Strong metal-support interactions (SMSI) between Ni and ZnO has a remarkable suppression effect on the methanation activity during the glycerol conversion.

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The role of functional materials to produce high areal capacity lithium sulfur battery Masud Rana, Bin Luo, Mohammad Rejaul Kaiser, Ian Gentle, Ruth Knibbe 2020, 42(3): 195-209.  DOI: 10.1016/j.jechem.2019.06.015 摘要 ( 13 )   The lithium sulfur batteries (LSBs) are considered as one of the promising next generation energy storage devices due to the high theoretical specific capacity of sulfur (1675 mAh g-1), naturally available, low cost. However, the practical LSBs are impeded by the well-known "shuttle effect" combined with other technical drawbacks. The "shuttle effect" causes rapid capacity decay, severe self-discharging and low active material utilization. The polysulfide (PS) which has lone pair electrons in each sulfur atom is considered as Lewis base and shows strong affinity to various polar, Lewis acid and catenation interactive materials but very weakly interacts with the non-polar conductive carbons. The "shuttle effect" occurs due to the diffusion of high order PS from the cathode to the anode and then low-order PS back to the cathode. The PS is polar and, due to a lone pair of electrons associated with the sulfur atom, is considered a Lewis base. As such, the PS shows a strong affinity with various polar and Lewis acid materials. In addition, a more novel trapping can be performance through a catenation reaction. For LSBs to compete with the state-of-the-art lithium ion batteries (LIBs), the LSB areal capacity need to be ～6 mAh cm-2 (which is proportional to sulfur loading). To achieve this target the PS shuttling needs to mitigate, which can be achieved through using functional materials. This review addresses the aforementioned phenomena by considering the PS phase interacts with the various functional materials and how this impacts areal capacity and cycling stability of LSBs.

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TTA as a potential hole transport layer for application in conventional polymer solar cells Le Liu, Saisai Zhou, Chengjie Zhao, Tonggang Jiu, Fuzhen Bi, Hongmei Jian, Min Zhao, Guodong Zhang, Lejia Wang, Fenfen Li, Xunwen Xiao 2020, 42(3): 210-216.  DOI: 10.1016/j.jechem.2019.07.005 摘要 ( 14 )   Hole transport layers (HTLs) play a vital role in organic solar cells (OSCs). In this work, a derivative of tetrathiafulvalene with four carboxyl groups TTA was introduced as a novel HTL to fabricate OSC with high performance. Displaying a better energy level match between HTL and active layers, the TTA based devices show a peak power conversion efficiency of 9.09%, which is comparable to the devices based on PEDOT:PSS. The favorable surface morphology recorded via atomic force microscopy, low series loss and charge recombination indicated by electrochemical impedance spectroscopy, synchronously verify the potential of TTA for application in OSCs as a valid kind of HTLs.

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Polymer-free electrospun separator film comprising silica nanofibers and alumina nanoparticles for Li-ion full cell Syed Danish Ali Zaidi, Chong Wang, Qinjun Shao, Jing Gao, Shengdong Zhu, Haifeng Yuan, Jian Chen 2020, 42(3): 217-226.  DOI: 10.1016/j.jechem.2019.06.018 摘要 ( 9 )   A separator film for high-performance Li-ion batteries was prepared by electrospinning. The film had a hybrid morphology of silica nanofibers (SNFs) and alumina nanoparticles (ANPs), with a smooth surface, polymer-free composition, high porosity (79%), high electrolyte uptake (876%), and excellent thermal stability. Contact angle measurements demonstrated the better immersion capability of the SNF-ANP separator film for commercial liquid electrolytes than a commercial CELGARD 2500 separator film. Moreover, compared to the commercial CELGARD 2500 separator, the ionic conductivity of the SNF-ANP separator film was nearly three times higher, the bulk resistance was lower at elevated temperature (120℃), the interfacial resistance with lithium metal was lower, and the electrochemical window was wider. Full cells were fabricated to determine the cell performance at room temperature. The specific capacity of the full cell with the SNF-ANP separator film was 165 mAh g-1; the cell was stable for 100 charge/discharge cycles and exhibited a capacity retention of 99.9%. Notably, the electrospun SNF-ANP separator film can be safely used in Li-ion or Li-S rechargeable batteries.

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Effects of cobalt carbide on Fischer-Tropsch synthesis with MnO supported Co-based catalysts Fanfei Sun, Ruoou Yang, Zhaoming Xia, Yuqi Yang, Ziang Zhao, Songqi Gu, Dongshuang Wu, Yunjie Ding, Zheng Jiang 2020, 42(3): 227-232.  DOI: 10.1016/j.jechem.2019.07.007 摘要 ( 20 )   Cobalt carbide (Co2C) was considered as potential catalysts available for large-scale industrialization of transforming syngas (H2 and CO) to clean fuels. Herein, we successfully synthesized Co-based catalysts with MnO supported, to comprehend the effects of Co2C for Fischer-Tropsch synthesis (FTS) under ambient conditions. The huge variety of product selectivity which was contained by different active sites (Co and Co2C) has been found. Furthermore, density functional theory (DFT) shows that Co2C is efficacious of CO adsorption, whereas is weaker for H adsorption than Co. Combining the advantages of Co and Co2C, the catalyst herein can not only obtain more C5+ products but also suppress methane selectivity. It can be a commendable guide for the design of industrial application products in FTS.

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Synthesis and dehydrogenation properties of NaZn(BH4)3·en and NaZn(BH4)3·2en (en=ethylene diamine) Yong Wu, Yue Qi, Jie Zheng, Xingguo Li 2020, 42(3): 233-236.  DOI: 10.1016/j.jechem.2019.07.008 摘要 ( 11 )   Two new hydrogen storage compounds, NaZn(BH4)3·en and NaZn(BH4)3·2en (en=ethylene diamine) are synthesized by a solution method. They can release 6.4 wt% and 6.3 wt% pure hydrogen below 200℃, respectively, demonstrating the potential to be used as hydrogen carriers. Additionally, their dehydrogenation products, thermodynamics and kinetics are well characterized and analyzed. Results shows that the stronger Zn-N interactions and the Hδ+-Hδ- interactions are significant for their stability below 100℃, relatively low decomposition temperatures and elimination of gas impurities.