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2020, Vol. 41, No. 2　Online: 2020-02-15

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Breaking the lithium storage limit via independent bilayer units within 2D layer materials Ming Lu, Bingsen Zhang, Wei Zhang, Weitao Zheng 2020, 41(2): 1-2.  DOI: 10.1016/j.jechem.2019.03.019 摘要 ( 12 )

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Long-term open circuit microbial electrosynthesis system promotes methanogenesis Raúl Mateos, Adrián Escapa, María Isabel San-Martín, Heleen De Wever, Ana Sotres, Deepak Pant 2020, 41(2): 3-6.  DOI: 10.1016/j.jechem.2019.04.020 摘要 ( 15 )   Microbial electrosynthesis (MES) can potentially provide a mean for storing renewable energy surpluses as chemical energy. However, the fluctuating nature of these energy sources may represent a threat to MES, as the microbial communities that develop on the biocathode rely on the continuous existence of a polarized electrode. This work assesses how MES performance, product generation and microbial community evolution are affected by a long-period (6 weeks) power off (open circuit). Acetogenic and H2-producing bacteria activity recovered after reconnection. However, few days later syntrophic acetate oxidation bacteria and H2-consuming methanogens became dominant, producing CH4 as the main product, via electromethanogenesis and the syntrophic interaction between eubacterial and archaeal communities which consume both the acetic acid and the hydrogen present in the cathode environment. Thus, the system proved to be resilient to a long-term power interruption in terms of electroactivity. At the same time, these results demonstrated that the system could be extensively affected in both end product generation and microbial communities.

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Well-dispersed SnO2 nanocrystals on N-doped carbon nanowires as efficient electrocatalysts for carbon dioxide reduction Baohua Zhang, Lizhen Sun, Yueqing Wang, Si Chen, Jintao Zhang 2020, 41(2): 7-14.  DOI: 10.1016/j.jechem.2019.04.022 摘要 ( 7 )   The conversion of carbon dioxide into valuable organic compounds is a highly promising approach to address the energy issues and environmental problems (e.g., global warming). Herein, we presents a facile and efficient method to prepare highly dense and well-dispersed SnO2 nanocrystals on 1D N-doped carbon nanowires as advanced catalysts for the efficient electroreduction of CO2 to formate. The ultrasmall SnO2 coated on the N-doped carbon nanowires (SnO2@N-CNW) has been synthesized via the simple hydrothermal treatment coupled with a pyrolysis process. The unique structure enables to expose the active tin oxide and also provides the facile pathways for rapid transfer of electron and electrolyte along with the highly porous carbon foam composed with interconnected carbon nanowires. Therefore, SnO2@NCNW electrocatalyst exhibits good durability and high selectivity for formate formation with a Faradaic efficiency of ca. 90%. This work demonstrates a simple method to rationally design high-dense tin oxide nanocrystals on the conductive carbon support as advanced catalysts for CO2 electroreduction.

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Engineering the HER catalytic behavior of heteroatomdoped molybdenum disulfide via versatile partial cation exchange Zhaoyan Luo, Junjie Ge, Changpeng Liu, Wei Xing 2020, 41(2): 15-19.  DOI: 10.1016/j.jechem.2019.03.031 摘要 ( 11 )

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Significantly improved oxidation of bio-based furans into furan carboxylic acids using substrate-adapted whole cells Mao Wen, Xue-Ying Zhang, Min-Hua Zong, Ning Li 2020, 41(2): 20-26.  DOI: 10.1016/j.jechem.2019.04.025 摘要 ( 13 )   Furan carboxylic acids are important building blocks in polymer and fine chemical industries. In this work, a simple substrate adaptation strategy was applied to improve the catalytic performances of Comamonas testosteroni SC1588 cells for the synthesis of various furan carboxylic acids. It was found that biocatalytic synthesis of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) was substantially promoted by adding histidine and increasing cell concentrations. HMFCA was produced in a quantitative yield from 200 mM HMF in 24 h. Besides, the HMFCA yields of 71%-81% were achieved with the substrate concentrations up to 250-300 mM. It was firstly found that 4-tert-butylcatechol (TBC), as the stabilizer present in HMF, exerted a significantly detrimental effect on whole-cell catalytic synthesis of HMFCA at high substrate concentrations (more than 130 mM). In addition, a variety of furan carboxylic acids such as 2-furoic acid, 5-methyl-2-furancarboxylic acid and 5-methoxymethyl-2-furancarboxylic acid were synthesized with the yields up to 98%.

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P4S10 modified lithium anode for enhanced performance of lithium-sulfur batteries Meng Li, Xiaojun Liu, Qian Li, Zhaoqing Jin, Weikun Wang, Anbang Wang, Yaqin Huang, Yusheng Yang 2020, 41(2): 27-33.  DOI: 10.1016/j.jechem.2019.03.038 摘要 ( 4 )   To address the corrosion and dendrite issues of lithium metal anodes, a protective layer was ex-situ constructed by P4S10 modification. It was determined by X-ray photoelectron spectroscopy and Raman spectra that the main constituents of the protective layer were P4S10, Li3PS4 and other LixPySz type derivatives. The protective layer was proved to be effective to stabilize the interphase of lithium metal. With the modified Li anodes, symmetric cells could deliver stable Li plating/stripping for 16000 h; Li-S batteries exhibited a specific capacity of 520 mA h g-1 after 200 cycles at 1000 mA g-1 with average Coulombic efficiency of 97.9%. Therefore, introducing LixPySz based layer to protect Li anode provides a new strategy for the improvement of Li metal batteries.

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Gas electrodes with nickel based current collectors for molten carbonate electrolyte thermo-electrochemical cells Sathiyaraj Kandhasamy, Geir Martin Haarberg, Signe Kjelstrup, Asbjørn Solheim 2020, 41(2): 34-42.  DOI: 10.1016/j.jechem.2019.05.001 摘要 ( 5 )   Thermo-electrochemical cells with inexpensive molten carbonate electrolyte and (CO2|O2) gas electrodes allow the possible conversion of high temperature waste heat from industrial processes into electricity. The cell containing eutectic (Li,Na)2CO3 electrolyte with solid MgO dispersion delivers a large Seebeck coefficient of -1.7 mV/K. At present, the (CO2|O2) gas electrodes use metallic gold as current collectors in order to avoid the formation of interfering oxide layers during operation. For further reduction in energy generation cost, the gold current collectors should be replaced with an inexpensive and stable alternative. In this study, the suitability of the (molten carbonate fuel cell) MCFC's nickel-based cathodes to operate the molten-carbonate thermo-electrochemical cell, was investigated. Ni current collectors were examined in two different states, as NiO and as lithiated NiO (LixNi1-xO). The NiO phase shows higher stability than the LixNi1-xO while the Seebeck coefficient remains above -1.2 mV/K.

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Improved perovskite solar cell efficiency by tuning the colloidal size and free ion concentration in precursor solution using formic acid additive Lina Meng, Qingbo Wei, Zhou Yang, Dong Yang, Jiangshan Feng, Xiaodong Ren, Yucheng Liu, Shengzhong(Frank) Liu 2020, 41(2): 43-51.  DOI: 10.1016/j.jechem.2019.04.019 摘要 ( 16 )   Improving the quality of the perovskite active layer is crucial to obtaining high performance perovskite solar cells (PSCs). In this work, by introducing formic acid into the formamidinium lead iodide (FAPbI3) precursor solution, we managed to achieve reduced colloidal size in the solution, leading to more uniform deposition of FAPbI3 film with lower trap state density and higher carrier mobility. The solar cells based on the FAPbI3 absorber layer modified with formic acid show significantly better photovoltaic performance than that on the reference FAPbI3 film without formic acid. The device performance shows a close correlation with the colloidal size. Within the range studied from 6.7 to 1.0 nm, the smaller the colloidal size is, the higher the solar cell efficiency. More specifically, the cell efficiency is improved from 17.82% for the control cell without formic acid to 19.81% when 0.764 M formic acid was used. Formic acid has also been added into a CH3NH3PbI3 (MAPbI3) precursor solution, which exhibits a similar effect on the resulting MAPbI3 films and solar cells, with efficiency improved from 16.07% to 17.00%.

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Facile preparation of bi-functional iron doped mesoporous materials and their application in the cycloaddition of CO2 Dan Liu, Gang Li, Hongchen Guo, Jiaxu Liu 2020, 41(2): 52-59.  DOI: 10.1016/j.jechem.2019.05.005 摘要 ( 10 )   Two kinds of bi-functional transition metal doped mesoporous materials (Fe-HMS and Fe-MCM-41) are prepared using one-step hydrothermal method and then treated with hydrochloric acid ethanol solution. The N2 adsorption and HRTEM results show that both of Fe-HMS and Fe-MCM-41 possess mesoporous structure. The UV-vis results suggest that the Fe species are mainly located within the framework. The basicity of as-prepared samples was studied by temperature programmed desorption using CO2 as probe molecule (CO2-TPD). The catalytic performance of Fe-HMS and Fe-MCM-41 in CO2 cycloaddition largely depends on the amount of the accessible basic sites. The acid-base active sites, framework Fe and PDDA species cooperatively catalyze the CO2 cycloaddition for the production of cyclic carbonates under the condition without any co-catalyst. The conversion of epichlorohydrin (ECH) is 97.4% and the selectivity of chloropropene carbonate is 92.9% under optimal conditions. The approximate rate constant of cycloaddition reaction of CO2 with ECH under optimum reaction temperature is calculated. It is worth noting that the Fe-HMS material shows superior reusability than Fe-MCM-41. In addition, this work provides a facile way on the synthesis of bi-functional acid-base heterogeneous catalyst with outstanding catalytic performance for the fixation of CO2.

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Solar chemical looping reforming of methane combined with isothermal H2O/CO2 splitting using ceria oxygen carrier for syngas production Srirat Chuayboon, Stéphane Abanades, Sylvain Rodat 2020, 41(2): 60-72.  DOI: 10.1016/j.jechem.2019.05.004 摘要 ( 11 )   The chemical looping reforming of methane through the nonstoichiometric ceria redox cycle (CeO2/CeO2-δ) has been experimentally investigated in a directly irradiated solar reactor to convert both solar energy and methane to syngas in the temperature range 900-1050℃. Experiments were carried out with different ceria shapes via two-step redox cycling composed of endothermic partial reduction of ceria with methane and complete exothermic re-oxidation of reduced ceria with H2O/CO2 at the same operating temperature, thereby demonstrating the capability to operate the cycle isothermally. A parametric study considering different ceria macrostructure variants (ceria packed powder, ceria packed powder mixed with inert Al2O3 particles, and ceria reticulated porous foam) and operating parameters (methane flow-rate, reduction temperature, or sintering temperature) was conducted in order to unravel their impact on the bed-averaged oxygen non-stoichiometry (δ), syngas yield, methane conversion, and solar reactor performance. The ceria cycling stability was also experimentally investigated to demonstrate repeatable syngas production by alternating the flow between CH4 and H2O (or CO2). A decrease in sintering temperature of the ceria foam was beneficial for increasing syngas selectivity, methane conversion, and reactor performance. Increasing both CH4 concentration and reduction temperature enhanced δ with the maximum value up to 0.41 but concomitantly favored CH4 cracking reaction. The ceria reticulated porous foam showed better performance in terms of effective heat transfer, due to volumetric absorption of concentrated solar radiation and uniform heating with lower solar power consumption, thereby promoting the solar-to-fuel energy conversion efficiency that reached up to 5.60%. The energy upgrade factor achieved during cycle was up to 1.19. Stable patterns in the δ and syngas yield for consecutive cycles with the ceria foam validated material performance stability.

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Composite solid electrolyte of Na3PS4-PEO for all-solid-state SnS2/Na batteries with excellent interfacial compatibility between electrolyte and Na metal Xiaoyan Xu, Yuanyuan Li, Jun Cheng, Guangmei Hou, Xiangkun Nie, Qing Ai, Linna Dai, Jinkui Feng, Lijie Ci 2020, 41(2): 73-78.  DOI: 10.1016/j.jechem.2019.05.003 摘要 ( 17 )   High ionic conductivity and superior interfacial stability of solid electrolytes at the electrodes are crucial factors for high-performance all-solid-state sodium batteries. Herein, a composite solid electrolyte Na3PS4-polyethylene oxide is synthesized by the solution-phase reaction method with an improved ionic conductivity up to 9.4×10-5 S/cm at room temperature. Moreover, polyethylene oxide polymer layer is wrapped homogeneously on the surface of Na3PS4 particles, which could effectively avoid the direct contact between Na3PS4 electrolyte and sodium metal, thus alleviate their side reactions. We demonstrate that all-solid-state battery SnS2/Na with the composite solid electrolyte Na3PS4-polyethylene oxide delivers an enhanced electrochemical performance with 230 mAh/g after 40 cycles.

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Role of surface defects of carbon nanotubes on catalytic performance of barium promoted ruthenium catalyst for ammonia synthesis Yongcheng Ma, Guojun Lan, Wenzhao Fu, Ying Lai, Wenfeng Han, Haodong Tang, Huazhang Liu, Ying Li 2020, 41(2): 79-86.  DOI: 10.1016/j.jechem.2019.04.016 摘要 ( 24 )   Carbon nanotubes (CNTs) with abundant surface defects are prepared by a liquid oxidation and thermal annealing method. The defective CNTs-D supported Ba-Ru/CNTs-D catalysts exhibit superior catalytic performance in ammonia synthesis with a TOF be increased up to 0.30 s-1, which is 2.5 times of oxidized CNTs-O supported Ba-Ru/CNTs-O catalysts and 5 times of the Ba-Ru/CNTs. The characterizations by CO chemisorption, transmission electron microscope, Raman, and X-ray photoelectron spectroscopy revealed that the uniformly well dispersed Ru NPs can be stabilized on the defective sites of CNTs-D. The great improvement of the catalytic performance and stability of the Ba-Ru/CNTs-D is contributed to the strong interaction between Ru NPs and surface defect of the CNTs.

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High rate and cycling stable Li metal anodes enabled with aluminum-zinc oxides modified copper foam Songtao Lu, Zhida Wang, He Yan, Rui Wang, Ke Lu, Yingwen Cheng, Wei Qin, Xiaohong Wu 2020, 41(2): 87-92.  DOI: 10.1016/j.jechem.2019.04.024 摘要 ( 15 )   Metallic Li is a promising anode material for high energy density batteries but it suffers from poor stability and formation of unsafe dendrites. Previous studies demonstrated that 3D metal foams are able to improve the stability of Li metal but the properties of these foams are inherently limited. Here we report a facile surface modification approach via magnetron sputtering of mixed oxides that effectively modulate the properties of Cu foams for supporting Li metal with remarkable stability. We discovered that hybrid Li anodes with Li metal thermally infused to aluminum-zinc oxides (AZO) coated Cu foams have significantly improved stability and reactivity compared with pristine Li foils and Li infused to unmodified Cu foams. Full cells assembled with a LiFePO4 cathode and a hybrid anode maintained low and stable charge-transfer resistance (<50 Ω) during 500 cycles in carbonate electrolytes, and exhibited superior rate capability (~100 mAh g-1 at 20 C) along with better electrochemical reversibility and surface stability. The AZO modified Cu foams had superior mechanical strength and afforded the hybrid anodes with minimized volume change without the formation of dendrites during battery cycling. The rational construction of surface architecture to precisely control Li plating and stripping may have great implications for the practical applications of Li metal batteries.

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The effect of Al3+ coordination structure on the propane dehydrogenation activity of Pt/Ga/Al2O3 catalysts Qinqin Yu, Tie Yu, Hongyu Chen, Guangzong Fang, Xiulian Pan, Xinhe Bao 2020, 41(2): 93-99.  DOI: 10.1016/j.jechem.2019.04.027 摘要 ( 13 )   The effect of the Al2O3 structure on the performance of Pt/Ga/Al2O3 catalysts is investigated for the direct dehydrogenation of propane. The study unveils that the structure of Al3+ determines the bulk structure of catalysts, particularly a high content of coordinatively unsaturated Al3+ sites (penta-coordinated Al3+, denoted as Al3+penta) could lead to a remarkably improved dehydrogenation activity of the catalyst. The bulk characterization reveals that the sufficient amount of Al3+penta in Al2O3 benefit the dispersion of Pt and Ga2O3 on the Al2O3 support. At the same time, TPR results reveal that the presence of Pt facilitates the reduction of Ga2O3, likely due to the hydrogen spillover between the well dispersed Pt and Ga2O3, which consequently enhances the synergistic function between Pt and Ga2O3 in the dehydrogenation of propane. Recyclability tests demonstrate that the dehydrogenation activity stabilizes after three cycles over the Pt/Ga/Al2O3 catalyst.

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A semiconductor-electrochemistry model for design of high-rate Li ion battery Wei Zhang, Dong Wang, Weitao Zheng 2020, 41(2): 100-106.  DOI: 10.1016/j.jechem.2019.04.018 摘要 ( 111 )   For designing batteries with high-rate and long-life, electronic/ionic transport and reaction must be unified for metal oxide electrodes. However, it remains challenging for effectively integrating the whole substrate/active materials/electrolyte interfaces. Herein by taking Li ion battery as example, we propose a semiconductor-electrochemistry model by which a general but novel insight has been gained into interfacial effect in batteries. Different from those traditional viewpoints, this derived model lies across from physics to electrochemistry. A reaction driving force can be expressed in terms of Fermi energy change, based on the tradeoff between electronic and ionic concentration at the reaction interfacial region. Therefore, at thermodynamic-controlled interface I of substrate/electrode, increasing contact areas can afford higher activity for active materials. Whereas at kinetically-governed interface II of electrode/electrolyte or inside active materials, it is crucial to guarantee high-reaction Li ionic concentration, with which some sufficient reaction degrees can reach.

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Scaling law of hydrogen evolution reaction for InSe monolayer with 3d transition metals doping and strain engineering Chao Wang, Yanyu Liu, Jian Yuan, Ping Wu, Wei Zhou 2020, 41(2): 107-114.  DOI: 10.1016/j.jechem.2019.05.007 摘要 ( 18 )   Recently, two dimensional InSe attracts great attentions as potential hydrogen production photocatalysts. Here, comprehensive investigations on the hydrogen evolution reaction activity of InSe monolayer with 3d transition metal doping and biaxial strain were performed based on the density functional theory. Transition metal dopants significantly increase the bonding strength between H and Se, and then adjust the hydrogen adsorption free energy to 0.02 eV by Zn doping. The enhanced hydrogen evolution reaction activity results from less electron occupying H 1s-Se 4pz anti-bonding states, which is well correlated with the pz band center level. Importantly, the universal scalling law was proposed to descript the evolution of hydrogen adsorption free energy including both doping and strain effects. Moreover, with appropriate band alignment, optical absorption, and carriers separation ability, Zn doped InSe monolayer is considered as a promising candidate of visible-light photocatalyst for hydrogen production.

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Fast hydrogenation kinetics of acridine as a candidate of liquid organic hydrogen carrier family with high capacity Ming Yang, Xile Xing, Ting Zhu, Xuedi Chen, Yuan Dong, Hansong Cheng 2020, 41(2): 115-119.  DOI: 10.1016/j.jechem.2019.05.012 摘要 ( 51 )

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Platinum in-situ catalytic oleylamine combustion removal process for carbon supported platinum nanoparticles Qingying Zhao, Huanqiao Li, Xiaoming Zhang, Shansheng Yu, Suli Wang, Gongquan Sun 2020, 41(2): 120-125.  DOI: 10.1016/j.jechem.2019.05.006 摘要 ( 9 )   Colloidal synthesis method such as oleylamine (OAm)-stabilized process is of great interest for obtaining uniform and highly dispersed platinum nanoparticle catalysts, yet the ligand may unavoidably inhibit their electro-catalytic performance. Thus, fully removing these ligands is critical to activate catalyst surface. Previous research of OAm removal process pointed that thermal annealing was the most effective way in comparison with other methods such as chemical washing, UV-Ozone irradiation and cyclic voltammetry sweeping, but generally resulting in undesired growth of platinum nanoparticle. Few studies concerning a more efficient ligand removal process have been published yet. In this work we proposed a platinum in-situ catalytic OAm combustion strategy to elucidate the removal mechanism of OAm ligands in thermal process and the key experimental parameters were also optimized. In addition, heat flow signal based on differential scanning calorimetry (DSC) measurement as a sensitive indicator, is suggested to reveal the ligand removal efficiency, which is much more reliable than the traditional spectroscopy. In comparison with commercial Pt/C sample, such a surface clean Pt/C electrocatalyst has shown an enhanced specific activity for oxygen reduction reaction. Our removal strategy and the evaluation method are highly instructive to efficient removal of different organic ligands.

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High performance columnar-like Fe2O3@carbon composite anode via yolk@shell structural design Zhiming Zheng, Pei Li, Jason Huang, Haodong Liu, Yi Zao, Zhongli Hu, Li Zhang, Huixin Chen, Ming-Sheng Wang, Dong-Liang Peng, Qiaobao Zhang 2020, 41(2): 126-134.  DOI: 10.1016/j.jechem.2019.05.009 摘要 ( 8 )   Conversion-type reaction anode materials with high specific capacity are attractive candidates to improve lithium ion batteries (LIBs), yet the rapid capacity fading and poor rate capability caused by drastic volume change and low electronic conductivity greatly hinder their practical applications. To circumvent these issues, the successful design of yolk@shell Fe2O3@C hybrid composed of a columnar-like Fe2O3 core within a hollow cavity completely surrounded by a thin, self-supported carbon (C) shell is presented as an anode for high-performance LIBs. This yolk@shell structure allows each Fe2O3 core to swell upon lithiation without deforming the carbon shell. This preserves the structural and electrical integrity against pulverization, as revealed by in situ transmission electron microscopy (TEM) measurement. Benefiting from these structural advantages, the resulting electrode exhibits a high reversible capacity (1013 mAh g-1 after 80 cycles at 0.2 A g-1), outstanding rate capability (710 mAh g-1 at 8 A g-1) and superior cycling stability (800 mAh g-1 after 300 cycles at 4 A g-1). A Li-ion full cell using prelithiated yolk@shell Fe2O3@C hybrid as the anode and commercial LiCoO2 (LCO) as the cathode demonstrates impressive cycling stability with a capacity retention of 84.5% after 100 cycles at 1 C rate, holding great promise for future practical applications.

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Understanding of performance degradation of LiNi0.80Co0.10Mn0.10O2 cathode material operating at high potentials Sheng S. Zhang 2020, 41(2): 135-141.  DOI: 10.1016/j.jechem.2019.05.013 摘要 ( 46 )   Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich LiNi0.80Co0.10Mn0.10O2 (NCM811) cathode material. Although much effort has been made, mechanisms for the above problems are poorly understood. Studying the cycling and float-charging characteristics of Li/NCM811 cells in high voltage conditions (4.5 V and 4.7 V, respectively), in this work we find that nearly all known problems with NCM811 material can be attributed to the oxidation of lattice oxygen occurring in the capacity region corresponding to H2 → H3 phase transition. While contributing to overall capacity, the oxidation of lattice oxygen results in a loss of oxygen through oxygen evolution and relative reactions between active oxygen evolution intermediates and electrolyte solvents. It is the loss of oxygen that results in irreversible layered-spinel-rocksalt phase transition, secondary particle cracking, and performance degradation. The conclusions of this work suggest that the priority for further research on NCM811 material should give to the suppression of oxygen evolution, followed by the use of the anti-oxygen electrolyte being chemically stable against the active oxygen evolution intermediates.

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Polyoxometalates-engineered hydrogen generation rate and durability of Pt/CNT catalysts from ammonia borane Wenzhao Fu, Chen Han, Dali Li, Wenyao Chen, Jian Ji, Gang Qian, Weikang Yuan, Xuezhi Duan, Xinggui Zhou 2020, 41(2): 142-148.  DOI: 10.1016/j.jechem.2019.05.014 摘要 ( 8 )   Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates (POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid (STA), phosphotungstic acid (PTA) and molybdophosphoric acid (PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.

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Recent progress in fluorinated electrolytes for improving the performance of Li-S batteries Xiwen Wang, Yuqing Tan, Guohong Shen, Shiguo Zhang 2020, 41(2): 149-170.  DOI: 10.1016/j.jechem.2019.05.010 摘要 ( 26 )   Lithium-sulfur (Li-S) batteries represent a "beyond Li-ion" technology with low cost and high theoretical energy density and should fulfill the ever-growing requirements of electric vehicles and stationary energy storage systems. However, the sulfur-based conversion reaction in conventional liquid electrolytes results in issues like the so-called shuttle effect of polysulfides and lithium dendrite growth, which deteriorate the electrochemical performance and safety of Li-S batteries. Optimization of conventional organic solvents (including ether and carbonate) by fluorination to form fluorinated electrolytes is a promising strategy for the practical application of Li-S batteries. The fluorinated electrolytes, owing to the high electronegativity of fluorine, possesses attractive physicochemical properties, including low melting point, high flash point, and low solubility of lithium polysulfide, and can form a compact and stable solid electrolyte interphase (SEI) with the lithium metal anode. Herein, we review recent advancements in the development of fluorinated electrolytes for use in Li-S batteries. The effect of solvent molecular structure on the performance of Li-S batteries and the formation mechanism of SEI on the cathode and anode sides are analyzed and discussed in detail. The remaining challenges and future perspectives of fluorinated electrolytes for Li-S batteries are also presented.

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Li4-xSbxSn1-xS4 solid solutions for air-stable solid electrolytes Zhuoran Zhang, Jianxing Zhang, Yulong Sun, Huanhuan Jia, Linfeng Peng, Yunyang Zhang, Jia Xie 2020, 41(2): 171-176.  DOI: 10.1016/j.jechem.2019.05.015 摘要 ( 24 )   The sulfide solid electrolytes have the characteristics of high ionic conductivity and low grain boundary resistance, which make them suitable for bulk-type all-solid-state batteries. However, most of them suffer from poor stability in air. Here, we explore the air stable sulfide solid electrolytes in Li4SnS4-Li3SbS4 system. The solid solutions of Li4-xSbxSn1-xS4 (0 ≤ x ≤ 0.5) can be formed in Li4SnS4-Li3SbS4 system. Li3.8Sb0.2Sn0.8S4 achieves the highest ionic conductivity of 3.5×10-4 S cm-1 in this system, which is 5 times as that of Li4SnS4 and 3 orders of magnitude higher than that of Li3SbS4, respectively. Li3.8Sb0.2Sn0.8S4 crystallizes into the same structure with high ionic conductivity phase of β-Li3PS4. Moreover, Li3.8Sb0.2Sn0.8S4 owns good stability in humid air. Matching with LiCoO2 and Li4Ti5O12, Li3.8Sb0.2Sn0.8S4 exhibits the potential to be applied in all-solid-state batteries.

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A phosphotungstic acid coupled silica-Nafion composite membrane with significantly enhanced ion selectivity for vanadium redox flow battery Xiao-Bing Yang, Lei Zhao, Kokswee Goh, Xu-Lei Sui, Ling-Hui Meng, Zhen-Bo Wang 2020, 41(2): 177-184.  DOI: 10.1016/j.jechem.2019.05.022 摘要 ( 8 )   An ultra-high ion-selective Nafion composite membrane modified by phosphotungstic acid (PWA) coupled silica for vanadium redox flow battery (VRB) was constructed and prepared through solution casting. The composite membrane exhibits excellent proton conductivity and vanadium ions blocking property by incorporating the nanohybrid composed of silica and PWA into the Nafion ionomer. Simple tuning for the filling amount of the nanohybrid endows the obtained membranes preeminent vanadium barrier property including a minimum vanadium permeability of 3.13×10-7 cm2 min-1 and a maximum proton conductivity of 0.081 S cm-1 at 25℃. These indicate an ion selectivity of 2.59×105 S min cm-3, which is 6.8 times higher than that of recast Nafion (0.33×105 S min cm-3). As a result, the VRB with the composite membrane shows superior battery performance containing a lower self-discharge rate, higher capacity retention and more robust cyclic stability compared with recast Nafion over a range of current densities from 40 to 100 mA cm-2.

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Co3O4 modified Ag/g-C3N4 composite as a bifunctional cathode for lithium-oxygen battery Qi Guo, Chenwei Zhang, Chaofeng Zhang, Sen Xin, Pengchao Zhang, Qiufan Shi, Dawei Zhang, Ya You 2020, 41(2): 185-193.  DOI: 10.1016/j.jechem.2019.05.018 摘要 ( 12 )   Rechargeable lithium-oxygen (Li-O2) batteries have appeal to enormous attention because they demonstrate higher energy density than the state-of-the-art Li-ion batteries. Whereas, their practical application is impeded by several challenging problems, such as the low energy round trip efficiencies and the insufficient cycle life, due to the cathode passivation caused by the accumulation of discharge products. Developing efficient catalyst for oxygen reduction and evolution reactions is effective to reduce the overpotentials in Li-O2 cells. In our work, we report a Co3O4 modified Ag/g-C3N4 nanocomposite as a bifunctional cathode catalyst for Li-O2 cells. The g-C3N4 substrate prevents the accumulation of Ag and Co3O4 nanoparticles and the presence of Ag NPs improves the surface area of g-C3N4 and electronic conductivity, significantly improving the oxygen reduction/evolution capabilities of Co3O4. Due to a synergetic effect, the Ag/g-C3N4/Co3O4 nanocomposite demonstrates a higher catalytic activity than each individual constituent of Co3O4 or Ag/g-C3N4 for the ORR/OER on as catalysts in Li-O2 cells. As a result, the Ag/g-C3N4/Co3O4 composite shows impressive electrochemical performance in a Li-O2 battery, including high discharge capacity, small gap between charge and discharge potential, and high cycling stability.

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Remarkably reducing carbon loss and H2 consumption on Ni-Ga intermetallic compounds in deoxygenation of methyl esters to hydrocarbons Ning Zhao, Ying Zheng, Jixiang Chen 2020, 41(2): 194-208.  DOI: 10.1016/j.jechem.2019.05.019 摘要 ( 12 )   Ni-Ga alloy (Ni/Ga atomic ratio of 8), Ni3Ga and Ni5Ga3 intermetallic compounds (IMCs) catalysts were prepared from Ni-Mg-Al-Ga layered double hydroxides (LDHs) for the deoxygenation of methyl esters to hydrocarbons. In the alloy and IMCs, the presence of Ga reduced the surface Ni atom density, and the charge transfer from Ga to Ni increased the electron density of Ni. In the deoxygenation of methyl laurate, the Ni catalyst gave a complete hydrogenolysis of methyl laurate to CH4 at 330℃ and 3.0 MPa, while the presence of Ga promoted the HDO pathway and suppressed C-C bond hydrogenolysis and methanation. The Ni5Ga3 catalyst exhibited the best desired performance. Even at 400℃, it gave the yield of C11 and C12 hydrocarbons of ～99%, and the selectivity to CH4 (SCH4) was only 2.4%. In the deoxygenation of methyl octanoate and methyl palmitate, the Ni5Ga3 catalyst also gave the yield of hydrocarbons above 95%. Reactivity evaluation and methyl propionate-TPD and TPSR results indicate that the C-OCH3 bond instead of the O-CH3 one was cleaved on both Ni and bimetallic Ni-Ga catalysts. It is highlighted that methanol, derived from the C-OCH3 bond hydrogenolysis, mainly decomposed to CO and H2 on IMCs, while it was converted to methane on metallic Ni and alloy. It is of great significance that H2 could be yielded from the methyl ester itself. In short, the utilization of Ni-Ga IMCs can effectively reduce carbon loss and H2 consumption, all of which are ascribed to the geometric and electronic effects of Ga.

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In-situ growth of vertically aligned nickel cobalt sulfide nanowires on carbon nanotube fibers for high capacitance all-solid-state asymmetric fiber-supercapacitors Na Liu, Zhenghui Pan, Xiaoyu Ding, Jie Yang, Guoguang Xu, Linge Li, Qi Wang, Meinan Liu, Yuegang Zhang 2020, 41(2): 209-215.  DOI: 10.1016/j.jechem.2019.05.008 摘要 ( 10 )   Fiber-supercapacitors (FSCs) are promising power sources for miniature portable and wearable electronic devices. However, the development and practical application of these FSCs have been severely hindered by their low volumetric capacitance and narrow operating voltage. In this work, vertically aligned nickel cobalt sulfide (NiCo2S4) nanowires grown on carbon nanotube (CNT) fibers were achieved through an in-situ two-step hydrothermal reaction method. The as-prepared NiCo2S4@CNT fiber electrode exhibits a high volumetric capacitance of 2332 F cm-3, benefiting from its superior electric conductivity, large surface area, and rich Faradic redox reaction sites. Furthermore, a NiCo2S4@CNT//VN@CNT (vanadium nitride nanosheets grown on CNT fibers) asymmetric fiber-supercapacitor (AFSC) was successfully fabricated. The device exhibits an operating voltage up to 1.6 V and a high volumetric energy density of 30.64 mWh cm-3. The device also possesses outstanding flexibility as evidenced by no obvious performance degradation under various bending angles and maintaining high capacitance after 5000 bending cycles. This work promotes the practical application of flexible wearable energy-storage devices.

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Challenges and opportunities for using formate to store, transport, and use hydrogen Katarzyna Grubel, Hyangsoo Jeong, Chang Won Yoon, Tom Autrey 2020, 41(2): 216-224.  DOI: 10.1016/j.jechem.2019.05.016 摘要 ( 34 )   In this perspective article, the synthesis and thermodynamic properties of aqueous solutions of formate salts (FS, HCO2-) are described in relationship to the concept of H2 carriers. The physiochemical properties of solid FS, aqueous formate solutions, and aqueous bicarbonate solutions set the limitations for storage capacity, deliverable capacity, and usable H2 capacity of these H2 carriers, respectively. These parameters will help in the design of systems that use H2 carriers for storage and transport of H2 for fuel cell power applications. FS, as well as admixtures with formic acid (FA, H2CO2), have potential to address the goals outlined in the U.S. Department of Energy's H2@scale initiative to store in chemical bonds a significant quantity of energy (hundreds of megawatts) obtained from large scale renewable resources.