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2020, Vol. 50, No. 11　Online: 15 November 2020

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Tri-functionalized TiOxCl4-2x accessory layer to boost efficiency of hole-free, all-inorganic perovskite solar cells Qingwei Zhou, Jialong Duan, Yudi Wang, Xiya Yang, Qunwei Tang 2020, 50(11): 1-8.  DOI: 10.1016/j.jechem.2020.03.004 Abstract ( 8 )   PDF (7157KB) ( 1 )   Tin dioxide (SnO2) is generally regarded as a promising electron-transporting layer (ETL) for state-of-the- art perovskite solar cells (PSCs), however, the ubiquitous oxygen-vacancy-related defects at SnO2 surface and the large energy difference between conduction band of SnO2 and perovskite layer undoubtedly cause severe charge carrier recombination, resulting in sluggish charge extraction efficiency and non-negligible open-circuit voltage (Voc) loss. Herein, a chlorine-containing TiOxCl4-2x accessory layer is fabricated by immersing SnO2 layer into the TiCl4 aqueous solution to passivate the surface oxygen-vacancy-related defects of SnO2 layer and to set an intermediate energy level at ETL/perovskite interface in all-inorganic cesium lead tri-bromine (CsPbBr3) PSCs. Furthermore, the TiOxCl4-2x layer also improves the infiltration of SnO2 layer surface toward perovskite precursor for high-quality perovskite film. Finally, the hole-free, all- inorganic CsPbBr3 PSC with a structure of FTO/SnO2/TiOxCl4-2x/Cs0.91Rb0.09PbBr3/carbon achieves a cham- pion efficiency of 10.44% with a Voc as high as 1.629 V in comparison to 8.31% for control device. More- over, the optimized solar cell presents good stability in 80% humidity in air.

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Lithium-assisted synergistic engineering of charge transport both in GBs and GI for Ag-substituted Cu2ZnSn(S,Se)4 solar cells Xiangyun Zhao, Xiaohuan Chang, Dongxing Kou, Wenhui Zhou, Zhengji Zhou, Qingwen Tian, Shengjie Yuan, Yafang Qi, Sixin Wu 2020, 50(11): 9-15.  DOI: 10.1016/j.jechem.2020.03.007 Abstract ( 7 )   PDF (3099KB) ( 1 )   Although silver (Ag) substitution offers several benefits in eliminating bulk defects and facilitating inter- face type inversion for Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic (PV) technology, its further development is still hindered by the fairly low electrical conductivity due to the significant decrease of acceptors amount. In this work, a versatile Li-Ag co-doping strategy is demonstrated to mitigate the poor electrical conduc- tivity arising from Ag through direct incorporating Li via postdeposition treatment (PDT) on top of the Ag-substituted CZTSSe absorber. Depth characterizations demonstrate that Li incorporation increases p- type carrier concentration, improves the carrier collection within the bulk, reduces the defects energy level as well as inverts the electric field polarity at grain boundaries (GBs) for Ag-substituted CZTSSe system. Benefiting from this lithium-assisted complex engineering of electrical performance both in grain interior (GI) and GBs, the power conversion efficiency (PCE) is finally increased from 9.21% to 10.29%. This systematic study represents an effective way to overcome the challenges encountered in Ag substitution, and these findings support a new aspect that the synergistic effects of double cation dopant will further pave the way for the development of high efficiency kesterite PV technology.

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Ultraselective carbon molecular sieve membrane for hydrogen purification Ruisong Xu, Liu He, Lin Li, Mengjie Hou, Yongzhao Wang, Bingsen Zhang, Changhai Liang, Tonghua Wang 2020, 50(11): 16-24.  DOI: 10.1016/j.jechem.2020.03.008 Abstract ( 3 )   PDF (7778KB) ( 2 )   Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogen- containing mixtures is the key step in the production of hydrogen with high purity (>99.99%). In this work, carbon molecular sieve (CMS) membranes with ultrahigh permselectivity for hydrogen purification were fabricated by high-temperature (700-900 °C) pyrolysis of polymeric precursor of phenolphthalein- based cardo poly(arylene ether ketone) (PEK-C). The evolution of the microstructural texture and ultra- microporous structure and gas separation performance of the CMS membrane were characterized via TG-MS, FT-IR, XRD, TEM, CO2 sorption analysis and gas permeation measurements. CMS membranes pre- pared at 700 °C exhibited amorphous turbostratic carbon structures and high H2 permeability of 5260 Barrer with H2/CH4, H2/N2 and H2/CO selectivities of 311, 142, 75, respectively. When carbonized at 900 °C, the CMS membrane with ultrahigh H2/CH4 selectivity of 1859 was derived owing to the forma- tion of the dense and ordered carbon structure. CMS membranes with ultrahigh permselectivity exhibit an attractive application prospect in hydrogen purification.

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Fabrication of immobilized nickel nanoclusters decorated by CxNy species for cellulose conversion to C2,3 oxygenated compounds: Rational design via typical C- and N-sources Zhuqian Xiao, Xiaolei Wang, Qinqin Yang, Chuang Xing, Qing Ge, Xikun Gai, Jianwei Mao, Jianbing Ji 2020, 50(11): 25-36.  DOI: 10.1016/j.jechem.2020.02.054 Abstract ( 4 )   PDF (15145KB) ( 2 )   Production of chemicals and fuels from microcrystalline cellulose has inspired scholars’ attention. Deacti- vation of metallic catalysts including acid leaching and hydrothermal aggregation is still one of the core issues in these systems. To address these problems, we designed and fabricated a series of Ni-W/SiO2 catalysts, which were decorated by C N species using C- and N-sources and applied in cellulose con-version to C2,3 oxygenated compounds. The Ni-W/SiO2@CxNy catalysts, underwent complexing and self-assembling process, exhibited special heterojunctions, accompanying strong interactions mainly among Ni phase and CxNy layers. Catalytic results showed that the heterojunctions and outer CxNy layers extensively enhanced productions of hydroxyacetone (HDA) and ethylene glycol (EG) and promoted the hydrothermal stability through prospering in concentration of Lewis pairs from Ni-N—N structure and immobilizing the metallic nanoclusters. 48.25% of EG was yielded under 5.0 MPa H2 pressurized 240 °C water for 2.0 h. The Lewis pair further improved the formation of HDA with 20.92% yield. High hydrothermal stability of Ni- W/SiO2@CxNy catalyst was proved according to the recycling results and trace leaching concentration of Ni and W. This construction of metallic catalysts exploited a new strategy to manufacture extraordinary durability of metallic nanoclusters for cellulose conversion under harsh reaction conditions.

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Molybdenum carbide clusters for thermal conversion of CO2 to CO via reverse water-gas shift reaction Ying Ma, Zhanglong Guo, Qian Jiang, Kuang-Hsu Wu, Huimin Gong, Yuefeng Liu 2020, 50(11): 37-43.  DOI: 10.1016/j.jechem.2020.03.012 Abstract ( 5 )   PDF (7301KB) ( 2 )   Molybdenum carbides are highly active for CO2 conversion to CO via the reverse water-gas shift (RWGS) reaction, however the large grain size up to micrometers renders its relatively lower active sites utiliza-tion efficiency while generating CH4 as a by-product. In this work, a homogeneously dispersed molyb-denum carbide hybrid catalyst with sub-nanosized cluster (the average size as small as 0.5 nm) is pre-pared via a facile carbothermal treatment for highly selective CO2-CO reduction. The partially disordered Mo2C clusters are characterized by synchrotron high-resolution XRD and atomic resolution HAADF-STEM analysis, for which the source cause of the disorder is pinpointed by XAFS analysis to be the nitrogen intercalants from the carbonaceous precursor. The partially disordered Mo2C clusters show a RWGS rate as high as 184.4 μmol g-1Mo12 C s-1 at 400 °C with a superior selectivity toward CO (> 99.5%). This work highlights a facile strategy for fabricating highly dispersed and partially disordered Mo2C clusters at a sub-nano size with beneficial N-doping for delivering high catalytic activity and operational stability.

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Free-standing phosphorous-doped molybdenum nitride in 3D carbon nanosheet towards hydrogen evolution at all pH values Qiyou Wang, Yan Zhang, Wenpeng Ni, Yi Zhang, Tian Sun, Jiaheng Zhang, Junfei Duan, Yang Gao, Shiguo Zhang 2020, 50(11): 44-51.  DOI: 10.1016/j.jechem.2020.03.016 Abstract ( 2 )   PDF (4978KB) ( 1 )   Highly efficient electrocatalysts towards hydrogen evolution reaction (HER) with large current density at all-pH values are critical for the sustainable hydrogen production. Herein, we report a free-standing HER electrode, phosphorous-doped molybdenum nitride nanoparticles embedded in 3-dimentional car- bon nanosheet matrix (P-Mo2N-CNS) fabricated via one-step carbonization and in-situ formation. The as- prepared catalyst shows free-standing architecture with interconnected porous microstructure. P-doped Mo2N nanoparticles with an average diameter of 4.4 nm are well embedded in the 3-dimentional vertical carbon nanosheets matrix. Remarkable electrocatalytic HER performance is observed in alkaline, neutral and acidic media at large current densities. The overpotential of P-Mo2N-CNS to drive a current density of 100 mA cm-2 in 0.5 M H2SO4 and 1.0 M PBS is only 181 and 221 mV, respectively. In particular, the current density reaches up to 1000 mA cm-2 at a low overpotential of 256 mV in 1.0 M KOH, much better than that of the commercial Pt/C catalyst. Density functional theory calculations suggest the optimized H sorption kinetics on Mo2N after P doping, elucidating the superior activity.

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Core-shell-structured Co@Co4N nanoparticles encapsulated into MnO-modified porous N-doping carbon nanocubes as bifunctional catalysts for rechargeable Zn-air batteries Fengmei Wang, Huimin Zhao, Yiru Ma, Yu Yang, Bin Li, Yuanyuan Cui, Ziyang Guo, Lei Wang 2020, 50(11): 52-62.  DOI: 10.1016/j.jechem.2020.03.006 Abstract ( 5 )   PDF (8622KB) ( 2 )   Designing the highly catalytic activity and durable bifunctional catalysts toward oxygen reduc- tion/evolution reaction (ORR/OER) is paramount for metal-air batteries. Metal-organic frameworks (MOFs)-based materials have attracted a great deal of attention as the potential candidate for effectively catalyzing ORR/OER due to their adjustable composition and porous structure. Herein, we first introduce the Mn species into zeolitic-imidazole frameworks (ZIFs) and then further pyrolyze the Mn-containing bimetallic ZIFs to synthesize core-shell-structured Co@Co4N nanoparticles embedded into MnO-modified porous N-doped carbon nanocubes (Co@Co4N/MnO-NC). Co@Co4N/MnO-NC exhibits the outstanding cat- alytic activity toward ORR and OER which is attributed to its abundant pyridinic/graphitic N and Co4N, the optimized content of MnO species, highly dispersed catalytic sites and porous carbon matrix. As a result, the Co@Co4N/MnO-NC-based Zn-air battery exhibits enhanced performances, including the high discharge capacity (762 mAh gZn-1), large power density (200.5 mW cm-2), stable potential profile over 72 h, low overpotential (<1.0 V) and superior cycling life (2800 cycles). Moreover, the belt-shaped Co@Co4N/MnO-NC cathode-based Zn-air batteries are also designed which exhibit the superb electro- chemical properties at different bending/twisting conditions.

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A functional hyperbranched binder enabling ultra-stable sulfur cathode for high-performance lithium-sulfur battery Xiang Luo, Xianbo Lu, Xiaodong Chen, Ya Chen, Chunyang Yu, Dawei Su, Guoxiu Wang, Lifeng Cui 2020, 50(11): 63-72.  DOI: 10.1016/j.jechem.2020.02.041 Abstract ( 4 )   PDF (6177KB) ( 1 )   Binders are of vital importance in stabilizing the cathodes to enhance the cycling stability of lithium- sulfur (Li-S) batteries. However, conventional binders are typically confronted with the drawback of in- ability for adsorbing lithium polysulfide (LiPS), thus resulting in severe active material losing and rapid capacity fading. Herein, a novel water-soluble hyperbranched poly(amidoamine) (HPAA) binder with con- trollable hyperbranched molecular structure and abundant amino end groups for Li-S battery is designed and fabricated, which can improve efficient adsorption for LiPS and stability of the sulfur cathodes. Be- sides, the strong intermolecular hydrogen bonds in HPAA binder can contribute to the structural stability of S cathode and integration of the conductive paths. Therefore, the Li-S battery with this functional binder exhibits excellent cycle performance with a capacity retention of 91% after 200 cycles at 0.1 C. Even at a high sulfur loading of 5.3 mg cm-2, a specific capacity of 601 mA h g-1 can also be achieved. Density functional theory (DFT) calculation further demonstrates that the enhanced electrochemical sta- bility derives from the high binding energy between amino groups and LiPS and the wide electrochemical window (6.87 eV) of HPAA molecule. Based on the above all, this functional polymer will lighten a new species of binders for eco-friendly sulfur cathodes and significantly promote the practical applications of high-performance Li-S batteries.

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Balancing free and confined metallic Ni for an active and stable catalyst—A case study of CO methanation over Ni/Ni-Al2O3 Yong-Shan Xiao, Yong-Hong Song, Chang Liu, Xian-Ying Shi, Han-Qing Ge, Min-Li Zhu, Zhao-Tie Liu, Zhong-Wen Liu 2020, 50(11): 73-84.  DOI: 10.1016/j.jechem.2020.02.053 Abstract ( 4 )   PDF (6596KB) ( 1 )   We propose a new strategy to make an active and stable Ni-based catalyst which can be operated in a wide range of reaction temperatures. The ordered mesoporous alumina (OMA) with confined Ni in the pore wall (Ni-OMA) was prepared via the one-pot evaporation induced self-assembly method. By using the incipient impregnation method, different amounts of free Ni were loaded over Ni-OMA (Ni/Ni- OMA) at a fixed total NiO content of 15 wt%. Characterization results confirmed the formation of well- structured Ni-OMA, and the ordered structure was still well preserved even after impregnating NiO at a content of as high as 12 wt%. The catalysts were evaluated for the CO methanation as a model reaction under varied conditions. Importantly, the activity and stability of Ni/Ni-OMA for the titled reaction were significantly regulated by simply changing the ratio of the confined to free Ni. Over the optimum catalyst of NiO (2 wt%)/NiO (13 wt%)-OMA, the high activity at a temperature of as low as 300 °C was achieved with the space-time yield of methane over 7.6 g gcat-1 h-1 while a long-term stability for a time-on- stream of 400 h was confirmed without an observable deactivation under the conditions of 600 °C and an extremely high gas hourly space velocity of 120,000 mL g-1 h-1. The results were well explained as the integrated merits of the free Ni for a high dispersion and the confined Ni in OMA for the anti-sintering property.

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Roles of furfural during the thermal treatment of bio-oil at low temperatures Zhe Xiong, Yuanjing Chen, Muhammad Mufti Azis, Xun Hu, Wei Deng, Hengda Han, Long Jiang, Sheng Su, Song Hu, Yi Wang, Jun Xiang 2020, 50(11): 85-95.  DOI: 10.1016/j.jechem.2020.03.015 Abstract ( 10 )   PDF (9502KB) ( 3 )   The reactive O-containing species in bio-oil could induce the polymerization of bio-oil during its thermal treatment, which affects the relevant utilization of bio-oil significantly. Furans, as the highly reactive O- containing species in bio-oil, play important roles during the thermal treatment of bio-oil. In this study, furfural was chosen as the representative of the furans in bio-oil to investigate its roles during the ther- mal treatment of bio-oil. The raw bio-oil with and without the addition of extra furfural (10 wt% of bio-oil) and pure furfural were pyrolyzed in a fixed-bed reactor at 200-500 °C. The results show that the interactions among furfural and bio-oil components can take place prior to the evaporation of furfural (< 140 °C) to form the intermediates, then these intermediates could be further polymerized to form large molecular compounds, and coke can be formed via the interactions at temperatures ≥ 300 °C. At temper- atures ≤ 300 °C, furfural mainly interacts with anhydrosugars. As the temperature further increases, the aromatics are involved in the interactions to form coke. The increased percentage of the coke formed via the interactions is in a linear relation with the conversion of furfural during the pyrolysis at 300-500 °C (no coke formed at 200 °C). Meanwhile, more non-aromatic light components (≤ C6) and less aromatics in the tars could be formed due to the interactions.

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High efficient catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid under benign conditions with nitrogen-doped graphene encapsulated Cu nanoparticles Chaoxin Yang, Xiao Li, Zhenzhou Zhang, Bohan Lv, Jiachun Li, Zhenjian Liu, Wanzhen Zhu, Furong Tao, Guangqiang Lv, Yongxing Yang 2020, 50(11): 96-105.  DOI: 10.1016/j.jechem.2020.03.003 Abstract ( 4 )   PDF (5796KB) ( 1 )   Selective oxidation of 5-hydroxymethylfurfual (HMF) to 2,5-furandicarboxylic acid (FDCA) as a bioplas- tics monomer is efficiently promoted by a simple system without noble-metal and base additives. In this work, graphene oxide (GO) was first synthesised by an electrochemical method with flexible graphite pa- per (FGP) as start carbon material, then, nitrogen-doped graphene (NG) layers encapsulated Cu nanopar- ticles (NPs) was prepared by one-step thermal treatment of GO supported Cu2+ in flowing NH3 atmo-sphere. Compared with NG supported Cu NPs prepared by the traditional impregnation method, enhanced catalytic activity was achieved over Cu/NG and an FDCA yield of 95.2% was achieved under mild reaction conditions with tert-butylhydroperoxide (t-BuOOH) as the oxidant. Control experiments with different catalysts and different addition procedure of t-BuOOH showed the yield of HMF and various intermedi- ates during reaction. From the changing of intermediates concentrations and reaction rates, a reaction pathway through HMF-DFF-FFCA-FDCA was proposed. This work gives a more convenient, more green, more economical and effective method in encapsulated metal NPs preparation and high selectivity in HMF oxidation to FDCA under mild conditions.

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Hierarchically porous, ultrathin N-doped carbon nanosheets embedded with highly dispersed cobalt nanoparticles as efficient sulfur host for stable lithium-sulfur batteries Mengrui Wang, Xunfu Zhou, Xin Cai, Hongqiang Wang, Yueping Fang, Xinhua Zhong 2020, 50(11): 106-114.  DOI: 10.1016/j.jechem.2020.03.014 Abstract ( 5 )   PDF (5444KB) ( 1 )   The sluggish redox kinetics and shuttle effect of soluble polysulfides intermediate primarily restrict the electrochemical performance of lithium-sulfur (Li-S) batteries. To address this issue, rational design of high-efficiency sulfur host is increasingly demanded to accelerate the polysulfides conversion during charge/discharge process. Herein, we propose a macro-mesoporous sulfur host (Co@NC), which com- prises highly dispersed cobalt nanoparticles embedding in N-doped ultrathin carbon nanosheets. Co@NC is simply synthesized via a carbon nitride-derived pyrolysis approach. Owing to the highly conductive graphene-like matrix and well defined porous structure, the designed multifunctional Co@NC host en- ables rapid electron/ion transport, electrolyte penetration and effective sulfur trapping. More significantly, N heteroatoms and homogeneous Co nanocatalysts in the graphitic carbon nanosheets could serve as chemisorption sites as well as electrocatalytic centers for sulfur species. These Co-N active sites can syn- ergistically facilitate the redox conversion kinetics and mitigate the shuttling of polysulfides, thus leading to improved electrochemical cycling performance of Li-S batteries. As a consequence, the S/Co@NC cath- ode demonstrates high initial specific capacity (1505 mA h g-1 at 0.1 C) and excellent cycling stability at 1 C over 300 cycles, giving rise to a capacity retention of 91.7% and an average capacity decline of 0.03% cycle-1.

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Systematic approaches to improving the performance of polyoxometalates in non-aqueous redox flow batteries Yuan Cao, Jee-Jay J. Chen, Mark A. Barteau 2020, 50(11): 115-124.  DOI: 10.1016/j.jechem.2020.03.009 Abstract ( 6 )   PDF (2900KB) ( 1 )   Polyoxometalates have been explored as multi-electron active species in both aqueous and non-aqueous redox flow batteries. Although non-aqueous systems in principle offer a wider voltage window for redox flow battery operation, realization of this potential requires a judicious choice of solvent as well as poly- oxometalate properties. We demonstrate here the superior performance of N,N-dimethylformamide (DMF) compared to acetonitrile as a solvent for redox flow batteries based on Li3PMo12O40. This compound dis- plays two 1-electron transfers in acetonitrile but can access an extra quasi-reversible 2-electron redox process in DMF. A cell containing 10 mM solution of Li3PMo12O40 in DMF produced a cell voltage of 0.7 V with 2-electron transfers (State of Charge = 60%) and showed a good cyclability. As a means to boost en- ergy density, operation of the redox flow battery at a higher concentration of 0.1 M Li3PMo12O40 produced cells with cell voltage of 0.6 V in acetonitrile and a cell voltage of 1.0 V in DMF; both showed excellent coulombic efficiencies of more than 90% over the course of 30 cycles. Energy density was also increased by employing an asymmetric cell with different polyoxometalates on each side to extend cell voltage. Li6P2W18O62 exhibited 3 quasi-reversible 2-electron transfers in the potential range between -2.05 V and -0.5 V vs. Ag/Ag+. 10 mM Li6P2W18O62/Li3PMo12O40 in DMF produced a cell with cell voltage of 1.3 V in- volving 4-electron transfers (State of Charge = 50%) with coulombic efficiency of nearly 100% and energy efficiency of nearly 70% throughout the test with more than 20 cycles. These promising results demon- strate proof-of-concept approaches to improving the performance of polyoxometalates in non-aqueous redox flow batteries.

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Fabrication of nanoporous Ni and NiO via a dealloying strategy for water oxidation catalysis Xiangrong Ren, Yiyue Zhai, Qi Zhou, Junqing Yan, Shengzhong Liu 2020, 50(11): 125-134.  DOI: 10.1016/j.jechem.2020.03.020 Abstract ( 2 )   PDF (6980KB) ( 1 )   Nickel oxides and (oxy)hydroxides are promising replacements for noble-metal-based catalysts owing to their high activity and good long-term stability for the oxygen evolution reaction (OER). Herein, we devel- oped nanoporous Ni by a method of combined rapid solidification and chemical dealloying. Subsequently, nanoporous NiO was obtained via heating treatment, the macropore and skeleton sizes of the NiO origi- nated from Ni10Al90 alloy are 100-300 nm and 80-200 nm, respectively. Benefiting from the multi-stage nanoporous structure and high specific surface area, the nanoporous NiO demonstrates an outstanding OER, reaching 20 mA cm-2 at an overpotential of 356 mV in 1 M KOH. The corresponding Tafel slope and apparent activation energy are measured to be 76.73 mV dec-1 and 29.0 kJ mol-1, respectively. Moreover, kinetic analysis indicates that the NiO catalyst shows pseudocapacitive characteristics, and the improved current is attributed to the high-rate pseudocapacitive behavior that efficiently maintains increased nickel redox cycling to accelerate the reaction rates. After 1000 cycles of voltammetry, the overpotential of the NiO decreases by 22 mV (j = 10 mA cm-2), exhibiting excellent stability and durability.

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Defect CTF derived Ru-based catalysts for high performance overall water splitting reaction Xu Gao, Yi-jing Gao, Sui-qin Li, Jun Yang, Gui-lin Zhuang, Sheng-wei Deng, Zi-Hao Yao, Xing Zhong, Zhong-zhe Wei, Jian-guo Wang 2020, 50(11): 135-142.  DOI: 10.1016/j.jechem.2020.03.022 Abstract ( 5 )   PDF (5678KB) ( 1 )   Research on water-splitting electrocatalysts is crucial to establishing a solution to the energy crisis. Herein, we report a facile bottom-up strategy for the preparation of high performance supported elec- trocatalysts for overall water-splitting reaction via a rationally designed defect covalent triazine frame- works (CTFs) support. Specifically, defect CTFs are obtained via binary-precursor polymerization, fol- lowed by loading Ru nanoparticles (Ru/D-CTFs-900) with high HER performance at a current density of 10 mA cm-2. The overpotential is only 17 mV. Calcination of the resultant Ru-RuO2/D-CTFs-300 in air, produces excellent OER performance with 190 mV overpotential (at 10 mA cm-2). Furthermore, overall water splitting measurements reveal the potential of 1.47 V, which is better than the majority of the reported Ru-based catalysts. Moreover, density functional theory calculation results show that excellent electrocatalytic properties are attributed to the synergistic effect of Ru nanoparticles and carbon support.

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NiCo-LDH/Ti3C2 MXene hybrid materials for lithium ion battery with high-rate capability and long cycle life Rui Zhang, Zhe Xue, Jiaqian Qin, Montree Sawangphruk, Xinyu Zhang, Riping Liu 2020, 50(11): 143-153.  DOI: 10.1016/j.jechem.2020.03.018 Abstract ( 5 )   PDF (16800KB) ( 1 )   Nickel/cobalt-layered double hydroxides (NiCo-LDH) have been attracted increasing interest in the appli- cations of anode materials for lithium ion battery (LIB), but the low cycle stability and rate performance are still limited its practice applications. To achieve high performance LIB, the surface-confined strat- egy has been applied to design and fabricate a new anode material of NiCo-LDH nanosheet anchored on the surface of Ti3C2 MXene (NiCo-LDH/Ti3C2). The ultra-thin, bended and wrinkled α-phase crystal with an interlayer spacing of 8.1 A˚ can arrange on the conductive substrates Ti3C2 MXene directly, resulting in high electrolyte diffusion ability and low internal resistance. Furthermore, chemical bond interactions between the highly conductive Ti3C2 MXene and NiCo-LDH nanosheets can greatly increase the ion and electron transport and reduce the volume expansion of NiCo-LDH during Li ion intercalation. As expected, the discharge capacity of 562 mAh g-1 at 5.0 A g-1 for 800 cycles without degradation can be achieved, rate capability and cycle performance are better than that of NiCo-LDH (~100 mAh g-1). Furthermore, the density function theory (DFT) calculations were performed to demonstrate that NiCo-LDH/Ti3C2 system can be used as a highly desirable and promising anode material for lithium ion battery.

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Status and prospect of garnet/polymer solid composite electrolytes for all-solid-state lithium batteries Liansheng Li, Yuanfu Deng, Guohua Chen 2020, 50(11): 154-177.  DOI: 10.1016/j.jechem.2020.03.017 Abstract ( 9 )   PDF (12596KB) ( 2 )   Solid polymer electrolytes (SPEs), such as polyethylene oxide (PEO), are characteristic of good flexibility and excellent processability, but they suffer from low ionic conductivity and small Li+ transference num- ber at ambient temperature. Inorganic solid electrolytes (ISEs), garnet-type Li7La3Zr2O12 and its deriva- tives (LLZO-based) in particular, possess high ionic conductivity at room temperature, wide electrochem- ical stability window, large Li+ transference number as well as good stability against Li metal anode. Nevertheless, lithium dendrites growth, interfacial contact issue and brittle nature of LLZO-based ceramic electrolytes prevent their practical applications. In response to these shortcomings, LLZO-based/polymer solid composite electrolytes (SCEs), taking complementary advantages of two kinds of electrolytes, and thus simultaneously improving the electrode wettability, ionic conductivity and mechanical strength, have been made to develop high-performance SCEs in recent years. Herein, the intrinsic properties and re- search progress of LLZO-based/polymer SCEs, including LLZO-based/PEO SCEs (LLZO-based/PEO SCEs with uniform dispersion of LLZO-based fillers and LLZO-based/PEO layered SCEs) and LLZO-based/novel poly- mers SCEs, are summarized. Besides, comprehensive updates on their applications in solid-state batteries are also presented. Finally, challenges and perspectives of LLZO-based/polymer SCEs for advanced all- solid-state lithium batteries (ASSLBs) are suggested. This review paper aims to provide systematic re- search progress of LLZO-based/polymer SCEs, to allow for more efficient and target-oriented research on improving LLZO-based/polymer SCEs.

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Visualizing the importance of oxide-metal phase transitions in the production of synthesis gas over Ni catalysts✩ Luis Sandoval-Diaz, Milivoj Plodinec, Danail Ivanov, Stéphane Poitel, Adnan Hammud, Hannah C. Nerl, Robert Schlögl, Thomas Lunkenbein 2020, 50(11): 178-186.  DOI: 10.1016/j.jechem.2020.03.013 Abstract ( 7 )   PDF (7431KB) ( 1 )   Synthesis gas, composed of H2 and CO, is an important fuel which serves as feedstock for industrially relevant processes, such as methanol or ammonia synthesis. The efficiency of these reactions depends on the H2: CO ratio, which can be controlled by a careful choice of reactants and catalyst surface chemistry. Here, using a combination of environmental scanning electron microscopy (ESEM) and online mass spec- trometry, direct visualization of the surface chemistry of a Ni catalyst during the production of synthesis gas was achieved for the first time. The insertion of a homebuilt quartz tube reactor in the modified ESEM chamber was key to success of the setup. The nature of chemical dynamics was revealed in the form of reversible oxide-metal phase transitions and surface transformations which occurred on the per- forming catalyst. The oxide-metal phase transitions were found to control the production of synthesis gas in the temperature regime between 700 and 900 °C in an atmosphere relevant for dry reforming of methane (DRM, CO2: CH4 =0.75). This was confirmed using high resolution transmission electron mi-croscopy imaging, electron energy loss spectroscopy, thermal analysis, and C18O2 labelled experiments. Our dedicated operando approach of simultaneously studying the surface processes of a catalyst and its activity allowed to uncover how phase transitions can steer catalytic reactions.

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Cage-like P4S3 molecule as promising anode with high capacity and cycling stability for Li+/Na+/K+ storage Denghu Wei, Jie Yin, Zhicheng Ju, Suyuan Zeng, Haibo Li, Wei Zhao, Yanyan Wei, Huaiyong Li 2020, 50(11): 187-194.  DOI: 10.1016/j.jechem.2020.03.021 Abstract ( 6 )   PDF (12654KB) ( 3 )   Phosphorus sulfide cage molecule based on P4S3 was investigated for the first time as anode material for the storage of alkali metal ions (Li+, Na+, K+). Such P4S3 sample was obtained in a large scale by a simple heating reaction of low-cost rep P and S. X-ray diffraction refinement analysis indicates that P4S3 sample possesses a defect rich molecule crystal structure with S/P atom ratio of 0.74. The P4S3 anode delivered a high reversible capacity of 1266 mAh g-1 for lithium-ion batteries at 0.1 A g-1 and good cycling performance. Experimental results demonstrated that the P4S3 anode undergoes a reversible Li- storage reaction of P4S3 + 11 Li+ + 11 e- ↔ 0.5 Li4P2S6 + 3 Li3P during cycling. It also exhibited a high capacity of 1002 and 378 mAh g-1 at 0.1 A g-1 for Na+ and K+ storage, respectively. These properties suggest the promising application of P4S3 anode in high energy batteries.

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A new catalyst for urea oxidation: NiCo2S4 nanowires modified 3D carbon sponge Biaopeng Li, Congying Song, Jianjun Rong, Jing Zhao, Hong-En Wang, Ping Yang, Ke Ye, Kui Cheng, Kai Zhu, Jun Yan, Dianxue Cao, Guiling Wang 2020, 50(11): 195-205.  DOI: 10.1016/j.jechem.2019.12.018 Abstract ( 14 )   PDF (8826KB) ( 5 )   Urea oxidation is a significant reaction for utilizing urea-rich wastewater or human urine as sustainable power sources which can ease the water eutrophication while generate electricity. A direct urea-hydrogen peroxide fuel cell is a new kind of fuel cell employing urea as fuel and hydrogen peroxide as oxidant which possesses a larger cell voltage. Herein, this work tries to promote the kinetics process of urea oxi- dation by preparing low-cost and high-efficient NiCo2S4 nanowires modified carbon sponge electrode. The carbon sponge used in this work with a similar three-dimensional multi-channel structure to Ni foam, is prepared by carbonizing recycled polyurethane sponge which is also a process of recycling waste. The performance of the prepared catalyst in an alkaline solution is investigated in a three-electrode system. With the introduction of Co element to the catalyst, a reduced initial urea oxidation potential and a high performance are obtained. Furthermore, a direct urea-hydrogen peroxide fuel cell is assembled using the NiCo2S4 nanowires modified carbon sponge anode. Results indicate that the prepared catalyst provides a chance to solve the current problems that hinder the development of urea electrooxidation (high initial urea oxidation potential, low performance, and high electrode costs).

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Prussian blue and its analogues as advanced supercapacitor electrodes Emad S. Goda, Seungho Lee, Muhammad Sohail, Kuk Ro Yoon 2020, 50(11): 206-229.  DOI: 10.1016/j.jechem.2020.03.031 Abstract ( 13 )   PDF (20364KB) ( 5 )   Remarkable attention has been directed to Prussian blue (PB) and its analogues (PBA) as one of the most widely used metal-organic frameworks (MOFs) especially in the field of energy storage devices due to their fabulous features such as 3D open framework, high surface area, controllable distribution of pores and the low cost. Nevertheless, their depressed conductivity causes some insulation when being used as an electrode for supercapacitors leading to be restricted in further applications particularly the electron- ics. To the best of our knowledge, our review aimed primarily to give a total picture of the research that was done on utilizing PB and PBA for fabricating the electrodes of supercapacitor, studying their synthe- sis approaches in addition to the hybridization with other materials such as graphene, CNTs and con- ducting polymer. It also addresses the transformation of PB or PBA into other interesting nanostructures such as oxides, sulfides, and bicomponent of graphitic carbon nitride/metal oxides, as well. Furthermore, It exhibits various avenues for overcoming their disadvantages of bad cycle life, retention rate and not achieving the desired values of energy/power densities opening the door for enlarging the number of researches on their application as supercapacitors.

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Ligand engineering of colloid quantum dots and their application in all-inorganic tandem solar cells Fen Qiao, Yi Xie, Zhankun Weng, Huaqiang Chu 2020, 50(11): 230-239.  DOI: 10.1016/j.jechem.2020.03.019 Abstract ( 3 )   PDF (9052KB) ( 2 )   How to effectively utilize the energy of the broad spectrum of sunlight is one of the basic problems in the research of tandem solar cells. Due to their size effect, quantum confinement effect and coupling effect, colloidal quantum dots (QDs) exhibit new physical properties that bulk materials don’t possess. CdX (X = Se, S, etc.) and PbX (X = Se, S, etc.) QDs prepared by hot-injection methods have been widely studied in the areas of photovolitaic devices. However, the surfactants surrounding QDs seriously hinder the charge transport of QDs based solar cells. Therefore, how to fabricate high-performance tandem solar cells via ligands engineering has become a major challenge. In this paper, the latest progress of colloidal QDs in the research of all-inorganic tandem solar cells was summarized. Firstly, the improvement of QDs surface ligands and the optimization of ligands engineering were discussed, and the control of the physi- cal properties of QDs films were realized. From the aspects of colloidal QDs, ligand engineering, and solar cell preparation, the future development direction of colloidal QDs solar cells was proposed, providing technical guidances for the preparation of low-cost and high-efficiency nanocrystalline solar cells.

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High-loading Co-doped NiO nanosheets on carbon-welded carbon nanotube framework enabling rapid charge kinetic for enhanced supercapacitor performance Hao Xu, Yufang Cao, Yong Li, Pei Cao, Dandan Liu, Yongyi Zhang, Qingwen Li 2020, 50(11): 240-247.  DOI: 10.1016/j.jechem.2020.03.023 Abstract ( 5 )   PDF (6886KB) ( 2 )   Developing high power and energy supercapacitors (SCs) is a long-pursued goal for the applica- tion in transportation and energy storage station. Herein, a rationally-designed Co-doped nickel oxide nanosheets@carbon-welded carbon nanotube foam (Co-doped NiO@WCNTF) as freestanding electrode is successfully prepared for high power and energy SCs. The WCNTF framework with high specific sur- face area provides three dimensional highly conductive network for fast charge transport and ensures high loading of active materials (9.2 mg/cm2). Moreover, porous Co-doped NiO nanosheets uniformly anchored on the WCNTF framework enable rapid charge kinetics due to the high intrinsic conductivity of Co-doped NiO nanosheets and their good contact with conductive WCNTF substrate. As a result, the unique integrated electrode with 3D architecture exhibits an ultrahigh specific capacitance of 11.45 F/cm2 at 5 mA/cm2, outstanding rate capability (11.45 F/cm2 at 5 mA/cm2 and a capacitance retention of 86.2% at 30 mA/cm2) and good cycling stability, suggesting great potential for high performance supercapacitor.

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Multifunctional interlayer with simultaneously capturing and catalytically converting polysulfides for boosting safety and performance of lithium-sulfur batteries at high-low temperatures Xiao-Shuan Chen, You Gao, Guo-Rui Zhu, Hui-Jun Chen, Si-Chong Chen, Xiu-Li Wang, Gang Wu, Yu-Zhong Wang 2020, 50(11): 248-259.  DOI: 10.1016/j.jechem.2020.03.041 Abstract ( 7 )   PDF (7823KB) ( 2 )   Lithium-sulfur (Li-S) batteries as extremely promising high-density energy storage devices have attracted extensive concern. However, practical applications of Li-S batteries are severely restricted by not only intrinsic polysulfides shuttle resulting from their concentration gradient diffusion and sluggish conver- sion kinetics but also serious safety issue caused by thermolabile and combustible polymer separators. Herein, it is presented for the first time that a robust and multifunctional separator with urchin-like Co-doped FeOOH microspheres and multiwalled carbon nanotubes (MWCNTs) as an interlayer simultane- ously achieves to suppress polysulfides shuttle as well as improves thermotolerance and nonflammability of commercial PP separator. Accordingly, Li-S batteries with modified separator exhibit remarkable per- formance in a wide range temperatures of -25-100 °C. Typically, under 25 °C, ultrahigh initial capacities of 1441 and 827.29 mA h g-1 at 1 C and 2 C are delivered, and remained capacities of 936 and 663.18 mA h g-1 can be obtained after 500 cycles, respectively. At 0.1 C, the S utilization can reach up to 97%. Sig- nificantly, at 1 C, the batteries also deliver an excellent performance with remained capacities of high to 862.3, 608.4 and 420.6 mA h g-1 after 100, 300 and 450 cycles under 75, 0 and -25 °C, respectively. This work provides a new insight for developing stable and safe high-performance Li-S batteries.

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Highly electroactive N-Fe hydrothermal carbons and carbon nanotubes for the oxygen reduction reaction R. G. Morais, N. Rey-Raap, J. L. Figueiredo, M. F. R. Pereira 2020, 50(11): 260-270.  DOI: 10.1016/j.jechem.2020.03.039 Abstract ( 6 )   PDF (5275KB) ( 2 )   Glucose-derived carbons were prepared by hydrothermal carbonization of glucose followed by carboniza- tion or activation to obtain carbon materials with different microporosities. These microporous carbons and carbon nanotubes (CNTs) were functionalized with melamine and/or iron(II) phthalocyanine (FePc) following three different methodologies: (i) Functionalization with melamine via thermal treatment, (ii) incorporation of the lowest amount of FePc reported in the literature via incipient wetness impregnation followed by thermal treatment and (iii) functionalization with melamine followed by FePc incorporation. The chemical and textural characterization of the prepared materials and their electrochemical assess- ment allowed to understand the role of microporosity in the incorporation of FePc and its effect on the oxygen reduction reaction (ORR). It was observed that FePc was preferentially incorporated inside the porous structure, especially in samples with more developed microporosity. However, functionalization with melamine modified the textural properties and the surface chemistry, favoring the incorporation of FePc on the surface. Regarding the electrochemical performance, the presence of FePc greatly enhanced the electroactivity of the microporous catalysts. An onset potential of 0.88 V and a four-electron pathway were obtained for glucose-derived carbons, whereas the limiting current densities and kinetic current densities rose by 126% and 222%, respectively, in comparison to the base sample. Notwithstanding, the highest electrochemical activity was observed for the sample prepared with CNTs, due to the synergy between the active metal centers and their highly graphitic carbon structure. The electrochemical pa- rameters of CNTFePc surpass the commercial Pt/C. The half-wave potential is 40 mV higher, the limiting current density increases by 17%, and a negligible production of by-products (< 1%) was observed.

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One-time sintering process to modify xLi2MnO3 (1-x)LiMO2 hollow architecture and studying their enhanced electrochemical performances Renheng Wang, Yiling Sun, Kaishuai Yang, Junchao Zheng, Yan Li, Zhengfang Qian, Zhenjiang He, Shengkui Zhong 2020, 50(11): 271-279.  DOI: 10.1016/j.jechem.2020.03.042 Abstract ( 3 )   PDF (8637KB) ( 2 )   To solve the critical problems of lithium rich cathode materials, e.g., structure instability and short cycle life, we have successfully prepared a ZrO2-coated and Zr-doping xLi2MnO3•(1-x)LiMO2 hollow architec- ture via one-time sintering process. The modified structural materials as lithium-ion cathodes present good structural stability and superior cycle performance in LIBs. The discharge capacity of the ZrO2-coated and Zr-doped hollow pristine is 220 mAh g-1 at the 20th cycle at 0.2 C (discharge capacity loss, 2.7%) and 150 mAh g-1 at the 100th cycle at 1 C (discharge capacity loss, 17.7%), respectively. However, hollow pristine electrode only delivers 203 mAh g-1 at the 20th cycle at 0.2 C and 124 mAh g-1 at the 100th cycle at 1 C, respectively, and the corresponding to capacity retention is 92.2% and 72.8%, respectively. Diffusion coefficients of modified hollow pristine electrode are much higher than that of hollow pristine electrode after 100 cycles (approach to 1.4 times). In addition, we simulate the adsorption reaction of HF on the surface of ZrO2-coated layer by the first-principles theory. The calculations prove that the ad- sorption energy of HF on the surface of ZrO2-coated layer is about -1.699 eV, and the ZrO2-coated layer could protect the hollow spherical xLi2MnO3•(1-x)LiMO2 from erosion by HF. Our results would be appli- cable for systematic amelioration of high-performance lithium rich material for anode with the respect of practical application.

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Interfacial confinement of Ni-V2O3 in molten salts for enhanced electrocatalytic hydrogen evolution Jing Zhou, Hansheng Xiao, Wei Weng, Dong Gu, Wei Xiao 2020, 50(11): 280-285.  DOI: 10.1016/j.jechem.2020.03.048 Abstract ( 4 )   PDF (8570KB) ( 1 )   Implementation of non-precious electrocatalysts is key-enabling for water electrolysis to relieve chal- lenges in energy and environmental sustainability. Self-supporting Ni-V2O3 electrodes consisting of nanostrip-like V2O3 perpendicularly anchored on Ni meshes are herein constructed via the electrochem- ical reduction of soluble NaVO3 in molten salts for enhanced electrocatalytic hydrogen evolution. Such a special configuration in morphology and composition creates a well confined interface between Ni and V2O3. Experimental and Density-Functional-Theory results confirm that the synergy between Ni and V2O3 accelerates the dissociation of H2O for forming hydrogen intermediates and enhances the combination of H∗ for generating H2.

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Micrometer-sized ferrosilicon composites wrapped with multi-layered carbon nanosheets as industrialized anodes for high energy lithium-ion batteries Meng Li, Jingyi Qiu, Songtong Zhang, Pengcheng Zhao, Zhaoqing Jin, Anbang Wang, Yue Wang, Yusheng Yang, Hai Ming 2020, 50(11): 286-295.  DOI: 10.1016/j.jechem.2020.03.077 Abstract ( 6 )   PDF (6890KB) ( 2 )   Various nanostructured architectures have been demonstrated to be effective to address the issues of high capacity Si anodes. However, the scale-up of these nano-Si materials is still a critical obstacle for commercialization. Herein, we use industrial ferrosilicon as low-cost Si source and introduce a facile and scalable method to fabricate a micrometer-sized ferrosilicon/C composite anode, in which ferrosilicon microparticles are wrapped with multi-layered carbon nanosheets. The multi-layered carbon nanosheets could effectively buffer the volume variation of Si as well as create an abundant and reliable conductiv- ity framework, ensuring fast transport of electrons. As a result, the micrometer-sized ferrosilicon/C anode achieves a stable cycling with 805.9 mAh g-1 over 200 cycles at 500 mA g-1 and a good rate capability of 455.6 mAh g-1 at 10 A g-1. Therefore, our approach based on ferrosilicon provides a new opportunity in fabricating cost-effective, pollution-free, and large-scale Si electrode materials for high energy lithium-ion batteries.

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Extreme high reversible capacity with over 8.0 wt% and excellent hydrogen storage properties of MgH2 combined with LiBH4 and Li3AlH6 Wenping Lin, Xuezhang Xiao, Xuancheng Wang, Jie-Wei Wong, Zhendong Yao, Man Chen, Jiaguang Zheng, Zhencan Hu, Lixin Chen 2020, 50(11): 296-306.  DOI: 10.1016/j.jechem.2020.03.076 Abstract ( 4 )   PDF (12921KB) ( 1 )   Magnesium hydride has attracted great attention because of its high theoretical capacity and outstand- ing reversibility, nevertheless, its practical applications have been restricted by the disadvantages of the sluggish kinetics and high thermodynamic stability. In this work, an unexpected high reversible hydrogen capacity over 8.0 wt% has been achieved from MgH2 metal hydride composited with small amounts of LiBH4 and Li3AlH6 complex hydrides, which begins to release hydrogen at 276 °C and then completely de- hydrogenates at 360 °C. The dehydrogenated MgH2+LiBH4/Li3AlH6 composite can fully reabsorb hydrogen below 300 °C with an excellent cycling stability. The composite exhibits a significant reduction of dehy- drogenation activation energy from 279.7 kJ/mol (primitive MgH2) to 139.3 kJ/mol (MgH2+LiBH4/Li3AlH6), as well as a remarkable reduction of dehydrogenation enthalpy change from 75.1 kJ/mol H2 (primitive MgH2) to 62.8 kJ/mol H2 (MgH2+LiBH4/Li3AlH6). The additives of LiBH4 and Li3AlH6 not only enhance the cycling hydrogen capacity, but also simultaneously improve the reversible de/rehydrogenation kinet- ics, as well as the dehydrogenation thermodynamics. This notable improvement on the hydrogen ab- sorption/desorption behaviors of the MgH2+LiBH4/Li3AlH6 composite could be attributed to the dehydro- genated products including Li3Mg7, Mg17Al12 and MgAlB4, which play a key role on reducing the dehydro- genation activation energy and increasing diffusion rate of hydrogen. Meanwhile, the LiBH4 and Li3AlH6 effectively destabilize MgH2 with a remarkable reduction on dehydrogenation enthalpy change in terms of thermodynamics. In particular, the Li3Mg7, Mg17Al12 and MgAlB4 phases can reversibly transform into MgH2, Li3AlH6 and LiBH4 after rehydrogenation, which contribute to maintain a high cycling capacity. This constructing strategy can further promote the development of high reversible capacity Mg-based materials with suitable de/rehydrogenation properties.

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Surface charging activated mechanism change: A computational study of O, CO, and CO2 interactions on Ag electrodes Ilker Tezsevin, Mauritius C. M. van de Sanden, Süleyman Er 2020, 50(11): 307-313.  DOI: 10.1016/j.jechem.2020.03.080 Abstract ( 3 )   PDF (3420KB) ( 1 )   Electrocatalytic and plasma-activated processes receive increasing attention in catalysis. Density func- tional theory (DFT) calculations are state-of-the-art tools for the fundamental study of reaction mech- anisms and predicting the performance of catalytic materials. Proper application of DFT-based methods is crucial when investigating charge-doped electrode surfaces during electrocatalytic and plasma-activated reactions. Here, as a model electrode for plasma-activated CO2 splitting, we studied the interactions of O, CO, and CO2 with the neutral and progressively charged Ag(111) metal surfaces. We show that the ap- plication of correction procedures is necessary to obtain accurate adsorption energy profiles of O atoms, CO and CO2 molecules on Ag surfaces that are under the influence of additional electrons. Interestingly, the oxidation of CO is found to shift from a Langmuir-Hinshelwood mechanism on a neutral electrode to an Eley-Rideal mechanism on charged electrodes. Furthermore, we show that the surface charging of Ag(111) electrodes increase their CO2 reduction performance by enhancing the adsorption of O atoms and desorption of CO molecules. A further increase in the absolute charge-state of the electrode surface is expected to waive the thermodynamic barriers for the CO2 splitting reaction.

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CoxP@NiCo-LDH heteronanosheet arrays as efficient bifunctional electrocatalysts for co-generation of value-added formate and hydrogen with less-energy consumption Mei Li, Xiaohui Deng, Yue Liang, Kun Xiang, Dan Wu, Bin Zhao, Haipeng Yang, Jing-Li Luo, Xian-Zhu Fu 2020, 50(11): 314-323.  DOI: 10.1016/j.jechem.2020.03.050 Abstract ( 6 )   PDF (8419KB) ( 3 )   The inefficiency of water splitting is mainly due to the sluggish anodic water oxidation reaction. Re- placing water oxidation with thermodynamically more favorable selective methanol oxidation reaction and developing robust bifunctional electrocatalysts are of great significance. Herein, a hierarchical hetero- nanostructure with Ni-Co layered double hydroxide (LDH) ultrathin nanosheets coated on cobalt phos- phide nanosheets arrays (CoxP@NiCo-LDH) are fabricated and used for co-electrolysis of methanol/water to co-produce value-added formate and hydrogen with saving energy. Benefiting from the fast charge transfer introduced by phosphide nanoarrays, the synergy in nanosheets catalysts with hetero-interface, CoxP@NiCo-LDH/Ni foam (NF) exhibits superior electrocatalytic performance (10 mA cm-2 @1.24 V and -0.10 V for methanol selective oxidation and hydrogen evolution reaction, respectively). Furthermore, CoxP@NiCo-LDH/NF-based symmetric two-electrode electrolyzer drives a current density of 10 mA cm-2 with a low cell voltage of only 1.43 V and the Faradaic efficiency towards the generation of formate and H2 are close to 100% in the tested range of current density (from 40 to 200 mA cm-2). This work high- lights the positive effect of hetero-interaction in the design of more efficient eletrocatalysts and might guide the way towards facile upgrading of alcohols and energy-saving electrolytic H2 co-generation.

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Aluminum and phosphorus codoped “superaerophobic” Co3O4 microspheres for highly efficient electrochemical water splitting and Zn-air batteries Xian-Wei Lv, Yuping Liu, Wenwen Tian, Lijiao Gao, Zhong-Yong Yuan 2020, 50(11): 324-331.  DOI: 10.1016/j.jechem.2020.02.055 Abstract ( 5 )   PDF (13722KB) ( 2 )   Multifunctional non-precious catalysts for hydrogen/oxygen evolution reaction (HER/OER) and oxygen re- duction reaction (ORR) constitute the bottleneck in the applications in electrochemical overall water split- ting (OWS) and Zn-air batteries. Herein, a trifunctional electrocatalyst of urchin-like Al,P-codoped Co3O4 microspheres supported on Ni foam (denoted as AP-CONPs/NF) was fabricated via a hydrothermal process and subsequent low-temperature annealing and phosphorization, exhibiting enhanced OER, HER and ORR activities compared with single-doped and undoped samples. Their surface self-organized microstructure and excellent “superaerophobic” feature make a high bubble repellency, which boost diffusion of reac- tants and electrolyte-electrode intimate contact. The codoping of Al and P elements into Co3O4 betters right the balance among surface chemical state, the increased oxygen vacancies and the promoted charge transfer. Encouraged by these synergistic advantages, the AP-CONPs/NF was further employed as excel- lent bifunctional electrodes for the OWS (low cell voltage of 1.57 V at 10 mA cm-2) and as air cathode for rechargeable Zn-air batteries (high power density of 89.1 mW cm-2), which demonstrates a great feasibility for practical applications.

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Making fully printed perovskite solar cells stable outdoor with inorganic superhydrophobic coating Jianqiang Luo, Hong Bin Yang, Mingxiang Zhuang, Shujuan Liu, Liang Wang, Bin Liu 2020, 50(11): 332-338.  DOI: 10.1016/j.jechem.2020.03.082 Abstract ( 6 )   PDF (3219KB) ( 4 )   Outdoor environment including moisture, dust, UV, oxygen and thermal stress (repeated heating-cooling) is devastating to perovskite solar cells (PSCs). Here, we demonstrate a new strategy to make fully printed PSCs stable with maximum power output in outdoor environment by coating them with a porous hy- drophobic inorganic layer. After coating, the PSCs can maintain superior stability of more than 150 days of outdoor storage, 240 h of continuous operation at the maximum power output point in ambient air with relative humidity as high as ~80%, and stable operation for more than 10 h under raining condi- tion. ANSYS simulation shows that the thin and porous nature of the inorganic coating layer offers much better heat dissipation than conventional encapsulation methods using glasses attached by photocurable epoxy. A similar thermal expansion coefficient of the inorganic encapsulation material with the solar cell substrate can also prevent it from cracking after repeated heating-cooling cycles. All of these merits re- sulted from our encapsulation method endow the perovskite solar cells with the real outdoor working capability.

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The j-pH diagram of interfacial reactions involving H+ and OH- Fengjun Yin, Hong Liu 2020, 50(11): 339-343.  DOI: 10.1016/j.jechem.2020.03.078 Abstract ( 4 )   PDF (3774KB) ( 3 )   For aqueous interfacial reactions involving H+ and OH-, the interfacial pH varies dynamically during the reaction process, which is a key factor determining the reaction performance. Herein, the kinetic rele- vance between the interfacial pH and reaction rate is deciphered owing to the success in establishing the transport equations of H+/OH- in unbuffered solutions, and is charted as a current (j)-pH diagram in the form of an electrochemical response. The as-described j-pH interplay is experimentally verified by the oxygen reduction and hydrogen evolution reactions. This diagram serves to form a panoramic graphic view of pH function working on the interfacial reactions in conjunction with the Pourbaix’s potential-pH diagram, and particularly enables a kinetic understanding of the transport effect of H+ and OH- on the reaction rate and valuable instruction toward associated pH control and buffering manipulation.

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Fabrication of porous lithium titanate self-supporting anode for high performance lithium-ion capacitor Yan Liu, Wenqiang Wang, Jin Chen, Xingwei Li, Qilin Cheng, Gengchao Wang 2020, 50(11): 344-350.  DOI: 10.1016/j.jechem.2020.03.075 Abstract ( 4 )   PDF (5620KB) ( 1 )   Lithium titanate has unique “zero-strain” characteristics, which makes it promising for rapid energy stor- age lithium-ion capacitors. However, extremely low electronic conductivity and lithium ion diffusion coef- ficient severely limit its performance at high rate. Herein, we have constructed in situ clusters of porous lithium titanate nanoparticles on self-supporting carbon nanotube film by combining iron oxide hard template method and F127 soft template method. Due to the nano-structured particle size and the pen- etrating lithium ion transmission channel, a greatly improved lithium ion diffusion coefficient has been achieved, which brings significantly better electrochemical performance than dense lithium titanate. By assembling with a durable graphene foam cathode, a lithium-ion capacitor with an energy density of up to 101.8 Wh kg-1 was realized (at a power density of 436.1 W kg-1). And its capacitance retention reaches 84.8% after 5000 cycles. With such an alluring result, our work presents a novel lithium-ion ca- pacitor system with practical application prospects.

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Activation and surface reactions of CO and H2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions Liyuan Zhang, Xuanyu Zhang, Kun Qian, Zhaorui Li, Yongqiang Cheng, Luke L. Daemen, Zili Wu, Weixin Huang 2020, 50(11): 351-357.  DOI: 10.1016/j.jechem.2020.03.038 Abstract ( 5 )   PDF (6724KB) ( 4 )   Activation and surface reactions of CO and H2 on ZnO powders and nanoplates under CO hydrogenation reaction conditions were (quasi) in situ studied using temperature programmed surface reaction spec- tra, diffuse reflectance Fourier transform infrared spectroscopy, inelastic neutron scattering spectroscopy and electron paramagnetic resonance. CO undergoes disproportion reaction to produce gaseous CO2 and surface carbon adatoms, and adsorbs to form surface formate species. H2 adsorption forms dominant irreversibly-adsorbed surface hydroxyl groups and interstitial H species and very minor surface Zn-H species. Surface formate species and hydroxyl groups react to produce CO2 and H2, while surface car- bon adatoms are hydrogenated by surface Zn-H species sequentially to produce CH(a), CH2(a), CH3(a) and eventually gaseous CH4. The ZnO nanoplates, exposing a higher fraction of Zn-ZnO(0001) and O- ZnO(000-1) polar facets, are more active than the ZnO powders to catalyze CO hydrogenation to CH4. These results provide fundamental understanding of the reaction mechanisms and structural effects of CO hydrogenation reaction catalyzed by ZnO-based catalysts.

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Mild-condition synthesis of A2ZnH4 (A = K, Rb, Cs) and their effects on the hydrogen storage properties of 2LiH-Mg(NH2)2 Jirong Cui, Weijin Zhang, Hujun Cao, Ping Chen 2020, 50(11): 358-364.  DOI: 10.1016/j.jechem.2020.03.067 Abstract ( 3 )   PDF (5028KB) ( 1 )   In this paper, A2ZnH4 (A = K, Rb and Cs) have been synthesized for the first time by a new approach involving in two-step reactions, in which the target samples can be produced under mild conditions (160 °C for 4 h). What’s more, the additive effects of A2ZnH4 on the hydrogen storage properties of 2LiH-Mg(NH2)2 composite have been investigated systematically. Experimental results show that K2ZnH4 has the best comprehensive modification effects among these hydrides. The 2LiH-Mg(NH2)2-0.1K2ZnH4 sample shifts dehydrogenation peak temperature downwards by ca. 30 °C as compared to the pristine sample. In addition, about 70% extent of the theoretical hydrogen is able to desorb from the 0.1K2ZnH4 doped sample at 140 °C within 2 h, however, only 20% extent of hydrogen is liberated from the pure sample under the same conditions. The improved desorption kinetics is indicated by the reduced dehy- drogenation activation energy (Ea), the Ea of the 0.1K2ZnH4 doped sample is around 68 ± 1.0 kJ mol-1 which is 28% lower than that of the pristine one. Furthermore, the dehydrogenation mechanism of the K2ZnH4 doped sample has been proposed.

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Modulating charge separation and transfer kinetics in carbon nanodots for photoredox catalysis Pengju Yang, Zhidong Yang 2020, 50(11): 365-377.  DOI: 10.1016/j.jechem.2020.03.068 Abstract ( 6 )   PDF (10383KB) ( 2 )   Artificial photosynthesis has gained increasing interest as a promising solution to the worldwide energy and environmental issues. A crucial requirement for realizing a sustainable system for artificial pho- tosynthesis is to explore low cost, highly-efficient and stable photoactive materials. Carbon nanodots (CNDs) have attracted considerable attention owing to their low cost, tunable chemistry and unique light-harvesting capability. Previous review articles have highlighted the photocatalytic and photoelec- trocatalytic applications of CNDs and CNDs-based composite photocatalysts. However, the control of the separation and transfer processes of photogenerated electron/hole pairs in CNDs has not been reviewed. This review summarizes the recent progress in the design of CNDs as new light-harvesting materials and highlights their applications in photocatalytic hydrogen production, CO2 photoreduction and environmen- tal remediation. Strategies that have been employed to modulate the separation and transfer kinetics of photogenerated charge carriers in CNDs are discussed in detail. The challenges and new directions in this emerging area of research are also proposed.

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UiO-66 type metal-organic framework as a multifunctional additive to enhance the interfacial stability of Ni-rich layered cathode material Ruixue Xue, Na Liu, Liying Bao, Lai Chen, Yuefeng Su, Yun Lu, Jinyang Dong, Shi Chen, Feng Wu 2020, 50(11): 378-386.  DOI: 10.1016/j.jechem.2020.03.049 Abstract ( 5 )   PDF (9787KB) ( 1 )   To effectively alleviate the surface structure degradation caused by electrolyte corrosion and transition metal (TM) dissolution for Ni-rich (Ni content > 0.6) cathode materials, porous Zirconium based metal- organic frameworks (Zr-MOFs, UiO-66) material is utilized herein as a positive electrode additive. UiO-66 owns tunable attachment sites and strong binding affinity, making itself an efficient defluorination agent to suppress the undesirable reactions caused by fluorine species. Besides, it can also relieve TMs disso- lution and block the migration of TMs toward anode side since it’s a multifarious metal ions adsorbent, realizing both cathode and anode interface protection. Benefiting from these advantages, the UiO-66 as- sistant Ni-rich cathode achieves superior cycling stability. Particularly in full cell, the positive effects of this multifunctional additive are more pronounced than in the half-cell, that is after 400 cycles at 2 C, the capacity retention has doubled with the addition of UiO-66. More broadly, this unique application of functional additive provides new insight into the degradation mechanism of layered cathode materials and offers a new avenue to develop high-energy density batteries.

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Facile synthesis of hierarchical Na2Fe(SO4)2@rGO/C as high-voltage cathode for energy density-enhanced sodium-ion batteries Ge Yao, Xixue Zhang, Yongliang Yan, Jiyu Zhang, Keming Song, Juan Shi, Liwei Mi, Jinyun Zheng, Xiangming Feng, Weihua Chen 2020, 50(11): 387-394.  DOI: 10.1016/j.jechem.2020.03.047 Abstract ( 11 )   PDF (9084KB) ( 6 )   Fe-based sulfates are ideal cathode candidates for sodium-ion batteries (SIBs) owing to their high oper- ating voltage and low cost but suffer from the nature of poor power performance. Herein, a hierarchi- cal porous Na2Fe(SO4)2@reduced graphene oxide/carbon dot (Na2Fe(SO4)2@rGO/C) with low carbon con- tent (4.12 wt%) was synthesized via a facile homogeneous strategy benefiting for engineering application, which delivers excellent sodium storage performance (high voltage plateau of 3.75 V, 85 mAh g-1 and 330 Wh kg-1 at 0.05 C; 5805 W kg-1 at 10 C) and high Na+ diffusion coefficient (1.19 × 10-12 cm2 s-1). Moreover, the midpoint voltage of assembled full cell could reach 3.0 V. The electron transfer and re- action kinetics are effectively boosted since the nanoscale Na2Fe(SO4)2 is supported by a robust cross- linked carbon matrix with rGO sheets and carbon dots. The slight rGO sheets sufficiently enhance the electron transfer like a current collecter and restrain the aggregation, as well as ensure smooth ion chan- nels. Meanwhile, the carbon dots in the whole space connect with Na Fe(SO ) and help rGO to promote the conductivity of the electrode. Ex-situ X-ray powder diffraction and X-ray photoelectron spectrometry analysis confirm the high reversibility of this sodiation/desodiation process.

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NiCoP nanoleaves array for electrocatalytic alkaline H2 evolution and overall water splitting Lei Chen, Yaohao Song, Yi Liu, Liang Xu, Jiaqian Qin, Yongpeng Lei, Yougen Tang 2020, 50(11): 395-401.  DOI: 10.1016/j.jechem.2020.03.046 Abstract ( 8 )   PDF (9003KB) ( 2 )   The development of non-precious, high-efficient and durable electrocatalysts for H2 evolution in alkaline media is highly desirable. Herein we report NiCoP nanoleaves array vertically grown on Ni foam for H2 evolution and overall water splitting via simple hydrothermal treatment and phosphorization. The self- supported NiCoP nanoleaves architecture contributes to more exposed active sites, the smaller contact resistance between catalyst and substrate, faster ion diffusion and electron transfer. As a result, the op- timized electrode requires only overpotentials of 98 and 173 mV to achieve current densities of 10 and 100 mA cm-2 in 1.0 M KOH, respectively. Besides, used as both anode and cathode simultaneously, the electrode delivers current densities of 100 and 200 mA cm-2 at cell voltages of only 1.8 and 1.87 V, re- spectively. Moreover, the relatively high efficiency of about 11.4% for solar-driven water splitting further illustrates the application of our catalyst to sustainable development based on green technologies.

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Porous LaFeO3 nanofiber with oxygen vacancies as an efficient electrocatalyst for N2 conversion to NH3 under ambient conditions Chengbo Li, Dongwei Ma, Shiyong Mou, Yongsong Luo, Benyuan Ma, Siyu Lu, Guanwei Cui, Quan Li, Qian Liu, Xuping Sun 2020, 50(11): 402-408.  DOI: 10.1016/j.jechem.2020.03.044 Abstract ( 5 )   PDF (5641KB) ( 2 )   Electrocatalytic N2 reduction to NH3 under ambient conditions is an eco-friendly and sustainable alterna- tive to the traditional Haber-Bosch process. However, inhibited by the high activation barrier of N2, this process needs efficient electrocatalysts to adsorb and activate the N2, enabling the N2 reduction reaction (NRR). Herein, we report that porous LaFeO3 nanofiber with oxygen vacancies acts as an efficient NRR electrocatalyst with abundant active sites to enhance the adsorption and activation of N2. When tested in 0.1 M HCl, such electrocatalyst achieves a high Faradaic efficiency of 8.77% and a large NH3 yield rate of 18.59 μg h-1 mgcat.-1 at -0.55 V versus reversible hydrogen electrode. This catalyst also shows high long-term electrochemical stability and excellent selectivity for NH3 formation. Density functional theory calculations reveal that, by introducing oxygen vacancy on LaFeO3, the subsurface metallic ions are ex- posed with newly localized electronic states near the Fermi level, which facilitates the adsorption and activation of N2 molecules as well as the subsequent hydrogenation reactions.

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Selective hydrogenation of CO2 to methanol over Ni/In2O3 catalyst Xinyu Jia, Kaihang Sun, Jing Wang, Chenyang Shen, Chang-jun Liu 2020, 50(11): 409-415.  DOI: 10.1016/j.jechem.2020.03.083 Abstract ( 5 )   PDF (5384KB) ( 3 )   An In2O3 supported nickel catalyst has been prepared by wet chemical reduction with sodium borohy- dride (NaBH4) as a reducing agent for selective hydrogenation of carbon dioxide to methanol. Highly dis- persed Ni species with intense Ni-In2O3 interaction and enhanced oxygen vacancies have been achieved. The highly dispersed Ni species serve as the active sites for hydrogen activation and hydrogen spillover. Abundant H adatoms are thereby generated for the oxygen vacancy creation on the In2O3 surface. The enhanced surface oxygen vacancies further lead to improved CO2 conversion. As a result, an effective syn- ergy between the active Ni sites and surface oxygen vacancies on In2O3 causes a superior catalytic per- formance for CO2 hydrogenation with high methanol selectivity. Carbon monoxide is the only by product detected. The formation of methane can be ignored. When the reaction temperature is lower than 225 °C, the selectivity of methanol is 100%. It is higher than 64% at the temperature range between 225 °C and 275 °C. The methanol selectivity is still higher than 54% at 300 °C with a CO2 conversion of 18.47% and a methanol yield of 0.55 gMeOH gcat-1 h-1 (at 5 MPa). The activity of Ni/In2O3 is higher than most of the reported In2O3-based catalysts.

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Feasible engineering of cathode electrolyte interphase enables the profoundly improved electrochemical properties in dual-ion battery Wen-Hao Li, Hao-Jie Liang, Xian-Kun Hou, Zhen-Yi Gu, Xin-Xin Zhao, Jin-Zhi Guo, Xu Yang, Xing-Long Wu 2020, 50(11): 416-423.  DOI: 10.1016/j.jechem.2020.03.043 Abstract ( 2 )   PDF (7317KB) ( 1 )   Dual-ion battery (DIB) composed of graphite cathode and lithium anode is regarded as an advanced sec- ondary battery because of the low cost, high working voltage and environmental friendliness. However, DIB operated at high potential (usually ≥ 4.5 V versus Li+/Li) is confronted with severe challenges in- cluding electrolyte decomposition on cathode interface, and structural deterioration of graphite accom- panying with anions de-/intercalation, hinder its cyclic life. To address those drawbacks and preserve the DIB virtues, a feasible and scalable surface modification is achieved for the commercial graphite cathode of mesocarbon microbead. In/ex-situ studies reveal that, such an interfacial engineering facilitates and reconstructs the formation of chemically stable cathode electrolyte interphase with better flexibility alle- viating the decomposition of electrolyte, regulating the anions de-/intercalation behavior in graphite with the retainment of structural integrity and without exerting considerable influence on kinetics of anions diffusion. As a result, the modified mesocarbon microbead exhibits a much-extended cycle life with high capacity retention of 82.3% even after 1000 cycles. This study demonstrates that the interface modifica- tion of electrode and coating skeleton play important roles on DIB performance improvement, providing the feasible basis for practical application of DIB owing to the green and scalable coating procedures.

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Microstructural analyses of all-solid-state Li-S batteries using LiBH4-based solid electrolyte for prolonged cycle performance Kazuaki Kisu, Sangryun Kim, Ryuga Yoshida, Hiroyuki Oguchi, Naoki Toyama, Shin-ichi Orimo 2020, 50(11): 424-429.  DOI: 10.1016/j.jechem.2020.03.069 Abstract ( 2 )   PDF (3403KB) ( 3 )   Complex hydride materials have been widely investigated as potential solid electrolytes because they have good compatibility with the lithium metal anodes used in all-solid-state batteries. However, the de- velopment of all-solid-state batteries utilizing complex hydrides has been difficult as these cells tend to have short cycle lives. This study investigated the capacity fading mechanism of all-solid-state lithium- sulfur (Li-S) batteries using Li4(BH4)3I solid electrolytes by analyzing the cathode microstructure. Cross- sectional scanning electron microscopy observations after 100 discharge-charge cycles revealed crack for- mation in the Li4(BH4)3I electrolyte and an increased cathode thickness. Raman spectroscopy indicated that decomposition of the Li4(BH4)3I solid electrolyte occurred at a constant rate during the cycling tests. To combat these effects, the cycle life of Li-S batteries was improved by increasing the amount of solid electrolyte in the cathode.