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2020, Vol. 49, No. 10　Online: 2020-10-15

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Au-Ag alloy nanoparticles with tunable cavity for plasmon-enhanced photocatalytic H2 evolution Xuanyu Yue, Juan Hou, Haifeng Zhao, Pengcheng Wu, Yali Guo, Qin Shi, Long Chen, Shanglong Peng, Zhiyong Liu, Guozhong Cao 2020, 49(10): 1-7.  DOI: 10.1016/j.jechem.2020.01.005 摘要 ( 57 )   Au-Ag alloy nanoparticles with different cavity sizes have great potential for improving photocatalytic performance due to their tunable plasmon effect.In this study,galvanic replacement was combined with co-reduction with the reaction kinetics processes regulated to rapidly synthesize Au-Ag hollow alloy nanoparticles with tunable cavity sizes.The position of the localized surface plasmon resonance (LSPR) peak could be effectively adjusted between 490 nm and 713 nm by decreasing the cavity size of the Au-Ag hollow nanoparticles from 35 nm to 20 nm.The plasmon-enhanced photocatalytic H2 evolution of alloy nanoparticles with different cavity sizes was investigated.Compared with pure P25 (TiO2),intact and thin-shelled Au-Ag hollow nanoparticles (HNPs)-supported photocatalyst exhibited an increase in the photocatalytic H2 evolution rate from 0.48 μmol h-1 to 4 μmol h-1 under full-spectrum irradiation.This improved photocatalytic performance was likely due to the plasmon-induced electromagnetic field effect,which caused strong photogenerated charge separation,rather than the generation of hot electrons.

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Unraveling the electrocatalytically active sites and stability of Co & Co oxides on nanocarbon for oxygen evolution reaction in acid solution Yansong Zhu, Tianran Zhang, Tao An, Yun Zong, Jim Yang Lee 2020, 49(10): 8-13.  DOI: 10.1016/j.jechem.2020.01.026 摘要 ( 21 )   The oxygen evolution reaction (OER) in acid solution is a significant challenge for non-precious metal electrocatalysts based on the transition metals although they have shown good OER performance in alkaline solution.In this study,we synthesized the electrocatalysts containing two or three Co species (Co,CoO and Co3O4) nanoparticles on porous graphitic carbon (PGC) nanosheets which were prepared by a facile and low-cost synthesis where Co(NO3)2·6H2O and glucose were pyrolyzed in the presence of sodium chloride template.The Co3O4-dominated catalyst as-prepared,Co3O4/PGC,is OER active in acid solution (1.74 V at a current density of 10 mA cm-2).We identified the OER active sites in the catalyst to be the Co3O4 nanoparticles rather than carbon-coated Co.Through comparative studies of the varied catalysts,we also proved that Co3O4 is catalytically more active than Co and CoO.The Co3O4/PGC catalyst,however,lost almost of all its activity after 100 voltammetric cycles in the 1.2-1.8 V voltage window.When the catalyst stability was examined potentiostatically at different potentials,the catalyst showed good stability at 1.4 V.The stability study also revealed the mechanism of the catalyst instability in acid was caused by Co3O4 reduction below 1.4 V and by Co3O4 oxidation above 1.4 V.1.4 V is therefore a unique potential where Co3O4 nanoparticles are neither oxidized nor reduced to be susceptible to acid dissolution.

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N-doped porous carbon hollow microspheres encapsulated with iron-based nanocomposites as advanced bifunctional catalysts for rechargeable Zn-air battery Ran Hao, Jin-Tao Ren, Xian-Wei Lv, Wei L, Yu-Ping Liu, Zhong-Yong Yuan 2020, 49(10): 14-21.  DOI: 10.1016/j.jechem.2020.01.007 摘要 ( 19 )   The design and development of low-cost,efficient,and stable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are desirable for rechargeable metal-air batteries.In this work,N-doped porous hollow carbon spheres encapsulated with ultrafine Fe/Fe3O4 nanoparticles (FeOx@N-PHCS) were fabricated by impregnation and subsequent pyrolysis,using melamine-formaldehyde resin spheres as self-sacrifice templates and polydopamine as N and C sources.The sufficient adsorption of Fe3+ on the polydopamine endowed the formation of Fe-Nx species upon high-temperature carbonization.The prepared FeOx@N-PHCS has advanced features of large specific surface area,porous hollow structure,high content of N dopants,sufficient Fe-Nx species and ultrafine FeOx nanoparticles.These features endow FeOx@N-PHCS with enhanced mass transfer and considerable active sites,leading to high activity and stability in catalyzing ORR and OER in alkaline electrolyte.Furthermore,the rechargeable Zn-air battery with FeOx@N-PHCS as air cathode catalyst exhibits a large peak power density,narrow charge-discharge potential gap and robust cycling stability,demonstrating the potential of the fabricated FeOx@N-PHCS as a promising electrode material for metal-air batteries.This new finding may open an avenue for rational design of bifunctional catalysts by integrating different active components within all-in-one catalyst for different electrochemical reactions.

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Enhanced performance in the direct electrocatalytic synthesis of ammonia from N2 and H2O by an in-situ electrochemical activation of CNT-supported iron oxide nanoparticles Shiming Chen, Siglinda Perathoner, Claudio Ampelli, Hua Wei, Salvatore Abate, Bingsen Zhang, Gabriele Centi 2020, 49(10): 22-32.  DOI: 10.1016/j.jechem.2020.01.011 摘要 ( 17 )   The direct electrocatalytic synthesis of ammonia from N2 and H2O by using renewable energy sources and ambient pressure/temperature operations is a breakthrough technology,which can reduce by over 90% the greenhouse gas emissions of this chemical and energy storage process.We report here an in-situ electrochemical activation method to prepare Fe2O3-CNT (iron oxide on carbon nanotubes) electrocatalysts for the direct ammonia synthesis from N2 and H2O.The in-situ electrochemical activation leads to a large increase of the ammonia formation rate and Faradaic efficiency which reach the surprising high values of 41.6 μg mgcat-1 h-1 and 17%,respectively,for an in-situ activation of 3 h,among the highest values reported so far for non-precious metal catalysts that use a continuous-flow polymer-electrolytemembrane cell and gas-phase operations for the ammonia synthesis hemicell.The electrocatalyst was stable at least 12 h at the working conditions.Tests by switching N2 to Ar evidence that ammonia was formed from the gas-phase nitrogen.The analysis of the changes of reactivity and of the electrocatalyst characteristics as a function of the time of activation indicates a linear relationship between the ammonia formation rate and a specific XPS (X-ray-photoelectron spectroscopy) oxygen signal related to O2- in iron-oxide species.This results together with characterization data by TEM and XRD suggest that the iron species active in the direct and selective synthesis of ammonia is a maghemite-type iron oxide,and this transformation from the initial hematite is responsible for the in-situ enhancement of 3-4 times of the TOF (turnover frequency) and NH3 Faradaic efficiency.This transformation is likely related to the stabilization of the maghemite species at CNT defect sites,although for longer times of preactivation a sintering occurs with a loss of performances.

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Electrochemical study of different membrane materials for the fabrication of stable,reproducible and reusable reference electrode Nawar K.Al-Shara, Farooq Sher, Sania Z.Iqbal, Zaman Sajid, George Z.Chen 2020, 49(10): 33-41.  DOI: 10.1016/j.jechem.2020.01.008 摘要 ( 10 )   Fabrication of stable,reproducible and reusable reference electrodes for low energy and high-temperature steam splitting is of great interest for hydrogen fuel production without anthropogenic carbon dioxide (CO2) emission.This study has been conducted for the detection of suitable material for the fabrication of novel reference electrode.In the present scenario,this research is designed to fabricate a novel nickel reference electrode by using operating conditions of eutectic molten hydroxide (NaOH-KOH,49-51 mol%) at temperature 300℃ in an ion-conducting membrane of alumina and mullite tube.Afterwards,the designed nickel reference electrode has been examined for its reusability and stability by using electrochemical technique and cyclic voltammetry.Five scans of cyclic voltammetry are performed for both membrane fabricated reference electrode.A slight positive shift in oxidation peaks is observed for mullite membrane electrode (64 mV from scan 1 to 5).The stability measurements are noted by changing the scan rate between 50 and 150 mV s-1.Furthermore,the results show that the Ni/Ni(OH)2 reference electrode covered with a mullite membrane is stable and reusable at 300℃ temperature without any deterioration.The stability and reusability of prepared nickel reference electrode covered by mullite tube in the eutectic molten hydroxide were up to 9 days to carry out an electrochemical investigation,while for alumina tube reference electrode the stability and reliability were up to 3 days.The internal electrolytic material and ionic conductance can play an important role for future studies with this reference electrode along with optimisation of temperature and scan rate parameters.

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Facile biphasic catalytic process for conversion of monoterpenoids to tricyclic hydrocarbon biofuels Shaoqu Xie, Trong H.Huynh, Peiyong Qin, Tianwei Tan, Hongfei Lin 2020, 49(10): 42-50.  DOI: 10.1016/j.jechem.2020.01.032 摘要 ( 6 )   Terpenoids have drawn much attention to scientists in synthesizing high-performance bio-jet fuels due to their ring structures,which feature potential high densities.Here,a facile biphasic catalytic process has been developed for the production of high-density tricyclic hydrocarbon biofuels from a monoterpenoid,1,8-cineole,using sulfuric acid (H2SO4) as the homogeneous catalyst.A ~100% conversion of 1,8-cineole and a >40% carbon yield of cyclic dimers were achieved at 100℃ within two hours.The mechanism for the acid-catalyzed conversion of 1,8-cineole to cyclic hydrocarbon dimers were explored.In particular,the formation of the diene intermediates and the following dimerization of dienes was essential to synthesize tricyclic terpene dimers.The biphasic catalytic process accelerated the deoxygenation rate and enabled the dimerization with the aid of organic solvent while controlling the reaction rates to avoid the formation of solid residues.Moreover,this process also facilitated the product separation by organic solvent extraction while enabling easy recycle of the homogenous catalysts.

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The removal of inevitable NOx species in catalysts and the selection of appropriate membrane for measuring electrocatalytic ammonia synthesis accurately Huimin Liu, Yidan Zhang, Jingshan Luo 2020, 49(10): 51-58.  DOI: 10.1016/j.jechem.2020.01.029 摘要 ( 32 )   Ammonia synthesis by electrocatalytic nitrogen reduction reaction (NRR) is considered as a promising alternative to the Haber-Bosch process.However,due to the extremely low ammonia yield and easily accessible extraneous contamination in the laboratory,NRR study always suffers from fluctuation and variability.Finding and eliminating all kinds of possible extraneous contamination is crucial to evaluate the performance of electrocatalytic ammonia synthesis accurately.In this work,we systematically explored two factors that affect NRR results but are easy to be ignored:the selection of membrane for NRR and the unconscious N-source in NRR catalysts.After series of experiments,we proposed a low-cost and almost pollution-free Celgard 3501 membrane as the separator for NRR to avoid the adsorption and release of ammonia by the membrane.In addition,we proposed a pre-reduction strategy to remove residual or adsorbed NOx contaminants in catalysts.These two solutions will help the community to evaluate the NRR activity more accurately.

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A systematical study on the electrodeposition process of metallic lithium Hailin Fan, Chunhui Gao, Huai Jiang, Qingyuan Dong, Bo Hong, Yanqing Lai 2020, 49(10): 59-70.  DOI: 10.1016/j.jechem.2020.01.013 摘要 ( 18 )   In this study,commercial copper (Cu) foil and Cu foam are used as the working electrodes to systematically investigate the electrochemical deposition and dissolution processes of metallic lithium (Li) on these electrodes;Li metal deposited on the Cu foil electrode is porous and loose.The surface solid electrolyte interface (SEI) film after dissolution from Li dendrites maintains a dendritic porous structure,resulting in a large volume effect of the electrode during the cycle.The Cu foam electrode provides preferential nucleation and deposition sites near the side surface of the separator;the difference in Li affinity results in a heterogeneous deposition and dendrite growth of metallic Li.

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Highly integrated sulfur cathodes with strong sulfur/high-strength binder interactions enabling durable high-loading lithium-sulfur batteries Arif Rashid, Xingyu Zhu, Gulian Wang, Chengzhi Ke, Sha Li, Pengfei Sun, Zhongli Hu, Qiaobao Zhang, Li Zhang 2020, 49(10): 71-79.  DOI: 10.1016/j.jechem.2020.01.031 摘要 ( 13 )   The development of high-sulfur-loading Li-S batteries is a key prerequisite for their commercial applications.This requires to surmount the huge polarization,severe polysulfide shuttling and drastic volume change caused by electrode thickening.High-strength polar binders are ideal for constructing robust and long-life high-loading sulfur cathodes but show very weak interfacial interaction with non-polar sulfur materials.To address this issue,this work devises a highly integrated sulfur@polydopamine/highstrength binder composite cathodes,targeting long-lasting and high-sulfur-loading Li-S batteries.The super-adhesion polydopamine (PD) can form a uniform nano-coating over the graphene/sulfur (G-S) surface and provide strong affinity to the cross-linked polyacrylamide (c-PAM) binder,thus tightly integrating sulfur with the binder network and greatly boosting the overall mechanical strength/conductivity of the electrode.Moreover,the PD coating and c-PAM binder rich in polar groups can form two effective blockades against the effusion of soluble polysulfides.As such,the 4.5 mg cm-2 sulfur-loaded G-S@PD-c-PAM cathode achieves a capacity of 480 mAh g-1 after 300 cycles at 1 C,while maintaining a capacity of 396 mAh g-1 after 50 cycles at 0.2 C when the sulfur loading rises to 9.1 mg cm-2.This work provides a system-wide concept for constructing high-loading sulfur cathodes through integrated structural design.

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High-performance PVDF-HFP based gel polymer electrolyte with a safe solvent in Li metal polymer battery Jing Jie, Yulong Liu, Lina Cong, Bohao Zhang, Wei Lu, Xinming Zhang, Jun Liu, Haiming Xie, Liqun Sun 2020, 49(10): 80-88.  DOI: 10.1016/j.jechem.2020.01.019 摘要 ( 242 )   Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) based gel polymer electrolytes are widely studied owing to their electrochemical stability and high dielectric constant.However,most gel polymer electrolytes show unsatisfied safety and interface compatibility due to excessive absorption of volatile and flammable liquid solvents.Herein,by using a safe solvent (N-methyl-2-pyrrolidone) with higher boiling (203℃) and flash points (95℃),we initiatively fabricate a flexible PVDF-HFP based gel polymer electrolyte.The obtained gel polymer electrolyte demonstrates a high ionic conductivity of 7.24×10-4 S cm-1,an electrochemical window of 5.2 V,and a high lithium transference number of 0.57.As a result,the synthesized polymer electrolyte exhibits a capacity retention of 70% after 500 cycles at 0.5 C,and a discharge capacity of 86 mAh g-1 even at a high current rate of 10 C for LiFePO4 based Li metal batteries.Moreover,a stable Li plating/stripping for more than 500 h is achieved under 0.1 mAh at both room temperature and 70℃.Our results indicate that the PVDF-HFP polymer electrolyte is promising for manufacturing safe and high-performance Li metal polymer batteries.

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Cryo-induced closely bonded heterostructure for effective CO2 conversion: The case of ultrathin BP nanosheets/g-C3N4 Guli Zhou, Jinman Yang, Xingwang Zhu, Qidi Li, Qing Yu, Wiam El-alami, Chongtai Wang, Yuanbin She, Junchao Qian, Hui Xu, Huaming Li 2020, 49(10): 89-95.  DOI: 10.1016/j.jechem.2020.01.020 摘要 ( 14 )   Black phosphorus (BP),an interesting and multi-functional non-metal material,has attracted widespread attention.In this work,2D BP/2D g-C3N4 heterostructure had been fabricated at extremely low temperature,which was used to reduce CO2 for the first time.With introduction of 2D BP,the separation of photogenerated holes and electrons was extremely boosted,and composites showed excellent photocatalytic performance (CO2 to CO).Meanwhile,the targeted composite could keep high selectivity for CO generation and CO generation rate can be up to 187.7 μmol g-1 h-1.The formation process of the unique heterostructure and the key factor affecting the photocatalytic performance were also discussed.This work provides a new approach for designing metal free photocatalyst,which is used for CO2 reduction.

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Current technology development for CO2 utilization into solar fuels and chemicals: A review Azeem Mustafa, Bachirou Guene Lougou, Yong Shuai, Zhijiang Wang, Heping Tan 2020, 49(10): 96-123.  DOI: 10.1016/j.jechem.2020.01.023 摘要 ( 54 )   The continuous consumption of fossil fuels causes two important impediments including emission of large concentrations of CO2 resulting in global warming and alarming utilization of energy assets.The conversion of greenhouse gas CO2 into solar fuels can be an expedient accomplishment for the solution of both problems,all together.CO2 reutilization into valuable fuels and chemicals is a great challenge of the current century.Owing to limitations in traditional approaches,there have been developed many novel technologies such as photochemical,biochemical,electrochemical,plasma-chemical and solar thermochemical.They are currently being used for CO2 capture,sequestration,and utilization to transform CO2 into valuable products such as syngas,methane,methanol,formic acid,as well as fossil fuel consumption reduction.This review summarizes different traditional and novel thermal technologies used in CO2 conversion with detailed information about their working principle,types,currently adopted methods,developments,conversion rates,products formed,catalysts and operating conditions.Moreover,a comparison of these novel technologies in terms of distinctive key features such as conversion rate,yield,use of earth metals,renewable energy,investment,and operating cost has been provided in order to have a useful review for future research direction.

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Experimental evaluation of thermolysis-driven gas emissions from LiPF6-carbonate electrolyte used in lithium-ion batteries Zhenghai Liao, Shen Zhang, Yikun Zhao, Zongjia Qiu, Kang Li, Dong Han, Guoqiang Zhang, Thomas G.Habetler 2020, 49(10): 124-135.  DOI: 10.1016/j.jechem.2020.01.030 摘要 ( 28 )   This paper performs an experimental evaluation of thermolysis-driven gases generated by the thermal decomposition of 1 M LiPF6+EC/DMC=1/1 v/v electrolytes at various decomposition temperatures,pyrolysis durations,and oxygen concentrations.Carried out in a home-built autoclave filled with pure helium,the experiment reveals that as the decomposition temperature increases,more types and larger quantities of gases will be released.Specifically,the experimental results demonstrate trends of logistic growth in the volume concentration of CO2,C2H6O,C2H4,CO,and C2H4O2 with the increase of decomposition temperature.With a prolonged pyrolysis duration,while volume concentrations of certain gases,such as CO2,C2H6O,C2H5F,and CO would increase,the concentration of C2H4O2 actually decreases.Moreover,concentrations of both C2H4 and C2H5F will first decrease and reach their minimum values at 1% v/v oxygen concentration,and then they would quickly climb back at higher oxygen concentrations,while the concentrations of C2H6 and C2H3F would decrease monotonically.It is envisioned that the detailed experimental results and findings on the gas generation pattern of 1 M LiPF6+EC/DMC=1/1 v/v electrolytes can facilitate the development of an early warning mechanism of thermal runaway based on gas sensing technology,which can be effectively applied to monitor the potential thermal failures of lithium-ion batteries with the same type of electrolyte and thus promote the thermal safety of battery packs in safety-critical applications.

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N-doped carbon nanotubes formed in a wide range of temperature and ramping rate for fast sodium storage Ruchao Wei, Man Huang, Wenzhe Ma, Baojuan Xi, Zhenyu Feng, Haibo Li, Jinkui Feng, Shenglin Xiong 2020, 49(10): 136-146.  DOI: 10.1016/j.jechem.2020.01.010 摘要 ( 10 )   Herein,nickel@nitrogen-doped carbon nanotubes (Ni@NCNTs) are prepared by a simple and reliable method with Ni-based complex as single-source precursor.Significantly,the formation of CNTs is not susceptible to the calcination temperature and ramping rate and Ni@NCNTs can be attained from 430 to 900℃ in an inert atmosphere.Then they are the first time to be applied as the anode material for sodium-ion batteries.The presence of Ni nanoparticles (NPs) facilitates the solid electrolyte interface film over the anode surface and improves the capacity retention of the host material,especially at the high rates.Furthermore,Na+ diffusion is reinforced after the introduction of Ni NPs.Ni@NCNTs obtained at 500℃ (Ni@NCNTs-500) exhibit the best capacity retention and rate capability.Kinetics analyses demonstrate the faster electron transportation and ion diffusion than others prepared at other temperatures.The surficial capacitance storage favors the fast electrochemistry kinetics.It delivers a high specific capacity (192 mA h g-1 at 0.5 A g-1),excellent cycling stability (103 mA h g-1 after 10,000 cycles at 10 A g-1),and outstanding high-rate capability up to 20 A g-1 (118 mA h g-1).The related full cells confirm a high energy density of 140 Wh kg-1 at 38.16 W kg-1 and 44.27 W h kg-1 at 762 W kg-1.

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Tuning of interactions between cathode and lithium polysulfide in Li-S battery by rational halogenation Samson O.Olanrele, Zan Lian, Chaowei Si, Shuo Chen, Bo Li 2020, 49(10): 147-152.  DOI: 10.1016/j.jechem.2020.01.015 摘要 ( 27 )   Li-S batteries have aroused intense interests as one of the most promising high-energy-density storage technology.However,the complex undesired shuttle effect induced by dissolution and diffusion of lithium polysulfide intermediates remains the major setback of this technology.Chemical modification of carbon cathode through heteroatom-doping is widely accepted as an effective method to inhibit the shuttle effect in Li-S battery cathode.Herein,using first principle calculations,we systematically examined the interaction between halogenated graphene and lithium polysulfide species.It is found that the halogen dopants (F,Cl,Br,I) significantly modify the local electronic structure of adsorption site and further induce a polarization to trap the polysulfides.Interestingly,a concave curve is observed from F to I for lithium polysulfide adsorption rather than a linear relation.The exceptions demonstrated from iodine dopant is carefully analyzed and attributed to its unique charge state.Moreover,boron as second dopant further strengthens the interaction between halogenated graphene and polysulfide molecule.Based on halogenation strategy,lithium polysulfide/cathode interactions are tuned in a wide range,which can also be of great importance to accelerate redox reaction in Li-S battery.Overall,an effective method by halogenation is verified to regulate the adsorption of lithium polysulfide and also enhance the reaction kinetics of the Li-S battery system.

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Cathodic activated stainless steel mesh as a highly active electrocatalyst for the oxygen evolution reaction with self-healing possibility Gui-Rong Zhang, Liu-Liu Shen, Patrick Schmatz, Konrad Krois, Bastian J.M.Etzold 2020, 49(10): 153-160.  DOI: 10.1016/j.jechem.2020.01.025 摘要 ( 26 )   The oxygen evolution reaction (OER) represents one of the major bottlenecks for broad-based applications of many clean energy storage/conversion technologies.The key to solving this problem lies in developing high-performing,cost effective and stable catalysts for the OER.Herein,we demonstrate that ubiquitous stainless steel mesh (SSM) materials activated by a facile cathodization treatment can be employed as a high performing OER catalyst,as showcased by the impressively low overpotentials of 275 and 319 mV to reach the benchmark current densities of 10 and 100 mA cm-2 (1.0 M KOH),respectively.Cathodized SSM also exhibits excellent performance in a two-electrode water electrolyzer,which requires a low cell voltage of 1.58 at 10 mA cm-2 and outperforms many of water electrolyzers using earth-abundant OER catalysts.Moreover,cathodized SSM with minor performance degradation after the stability test can also be readily healed by subjecting it to an additional cathodization treatment.It is disclosed that the superior performance of cathodized SSMs stems from the surface enrichment of OER active Ni (oxy)hydroxide,facile gas-bubble removal and transportation over the unique mesh-structured surfaces,while the abundant reservoir of nickel in the bulk allows healing of the catalyst by a facile cathodization.

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Facile synthesis of sulfurized polyacrylonitrile composite as cathode for high-rate lithium-sulfur batteries Jingwei Xiang, Zezhou Guo, Ziqi Yi, Yi Zhang, Lixia Yuan, Zexiao Cheng, Yue Shen, Yunhui Huang 2020, 49(10): 161-165.  DOI: 10.1016/j.jechem.2020.01.037 摘要 ( 46 )   Sulfurized polyacrylonitrile (SPAN) as a promising cathode material for lithium sulfur (Li-S) batteries has drawn increasing attention for its improved electrochemical performance in carbonate-based electrolyte.However,the relatively poor electronic and ionic conductivities of SPAN limit its high-rate and lowtemperature performances.In this work,a novel one-dimensional nanofiber SPAN (SFPAN) composite is developed as the cathode material for Li-S batteries.Benefitting from its one-dimensional nanostructure,the SFPAN composite cathode provides fast channels for the migration of ions and electronics,thus effectively improving its electrochemical performance at high rates and low temperature.As a result,the SFPAN maintains a high reversible specific capacity ~1200 mAh g-1 after 400 cycles at 0.3 A g-1 and can deliver a high capacity of ~850 mAh g-1 even at a high current density of 12.5 A g-1.What is more,the SFPAN can achieve a capacity of ~800 mAh g-1 at 0℃ and ~1550 mAh g-1 at 60℃,thus providing a wider temperature range of applications.This work provides new perspectives on the cathode design for high-rate lithium-sulfur batteries.

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Facile fabrication of ultrafine nickel-iridium alloy nanoparticles/graphene hybrid with enhanced mass activity and stability for overall water splitting Shen Zhang, Xing Zhang, Xuerong Shi, Feng Zhou, Ruihu Wang, Xiaoju Li 2020, 49(10): 166-173.  DOI: 10.1016/j.jechem.2020.02.022 摘要 ( 17 )   Developing active and durable electrocatalysts for overall water splitting is desirable but challenging to realize sustainable hydrogen production.Here,we report a facile and general method to prepare ultrafine nickel (Ni)-iridium (Ir) alloy nanoparticles/graphene hybrids for overall water splitting.The optimized hybrid with 4.9 wt% Ir exhibits much higher catalytic activity and durability than commercial 20 wt% Ir/C for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).Theoretical simulations reveal that the incorporation of Ir in metallic Ni lattice regulates hydrogen adsorption free energy to the optimum level,thus improving HER activity,while in situ generated amorphous Ir-Ni hydr(oxy)oxides around metallic Ni-Ir core have been demonstrated to be the active species under OER conditions,which switches OER rate-determining step to energy-favorable pathway.The overall water splitting electrolyzer assembled by the optimized electrocatalyst shows a low cell voltage of only 1.52 V and excellent stability to deliver a current density of 10 mA cm-2.This work provides a powerful strategy toward general synthesis of ultrafine alloy nanoparticles for high-performance overall water splitting.

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A laser synthesis of vanadium oxide bonded graphene for high-rate supercapacitors Jun Tang, Linfei Zhang, Xiongwei Zhong, Xinghui Wang, Feng Pan, Baomin Xu 2020, 49(10): 174-178.  DOI: 10.1016/j.jechem.2020.02.015 摘要 ( 18 )   Graphene is a type of promising electrode material for high-energy and high-power density supercapacitors,but its electrochemical performance is greatly limited by the restacking problem.In this work,we reported a facile approach to synthesis graphene with chemically bonded vanadium oxide (VOx) nanoparticles and demonstrated that chemically-bonded VOx nanoparticles can effectively prevent the graphene sheets from restacking and hence improve the electrochemical performance.The capacitance of VOx-bonded graphene increases to 272 F/g compared to 183 F/g of pristine graphene in 1 M H3PO4 aqueous electrolyte at 2 A/g.The VOx-bonded graphene also showed improved rate capability in both H3PO4 and ionic liquid electrolytes.The capacitance retention increases to 54.5% from 28.5% at 100 A/g (compare to 2 A/g) in H3PO4 and increases to 65.1% from 46.3% at 2 A/g (compare to 0.2 A/g) in neat ionic liquid.A high energy density of 84.4 Wh/kg is obtained within the voltage window of 4 V in ionic liquid.Even at a high-power density of 1000 W/kg,the VOx-bonded graphene shows a high energy density of 47.3 Wh/kg.

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SiO2 stabilizes electrochemically active nitrogen in few-layer carbon electrodes of extraordinary capacitance Feng Xu, Tianquan Lin, Jian Huang, I-Wei Chen, Fuqiang Huang 2020, 49(10): 179-188.  DOI: 10.1016/j.jechem.2020.02.024 摘要 ( 2 )   Pyrrolic and pyridinic N dopants can dramatically increase the electrochemical activities of carbon and conducting polymers.Although N-doped conducting polymers suffer from rapid degradation,their carbon counterpart of extraordinary capacitance has remarkable rate performance and cycling endurance thanks to carbon's excellent electrical conductivity.But high nitrogen content and high electrical conductivity are difficult to achieve in a high-surface-area carbon,because the high chemical vapor deposition (CVD) temperature required for obtaining high conductivity also destabilizes under-coordinated pyrrolic and pyridinic nitrogen and tends to lower the surface area.Here we resolve this dilemma by using SiO2 as an effective N-fixation additive,which stabilizes the N-rich nano few-layer sp2-carbon construct in 1000℃ CVD.This enables a scalable sol-gel/CVD fabrication process for few-layer carbon electrodes of extraordinary capacitance (690 F g-1).The electrodes have excellent rate performance and can maintain 90% of their initial capacitance after 30,000 cycles,thus potentially suitable for practical applications.

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In situ growth of 3D walnut-like nano-architecture Mo-Ni2P@NiFe LDH/NF arrays for synergistically enhanced overall water splitting Zhi Yang, Yu Lin, Feixiang Jiao, Jinhui Li, Jinlei Wang, Yaqiong Gong 2020, 49(10): 189-197.  DOI: 10.1016/j.jechem.2020.02.025 摘要 ( 24 )   The in situ growth of nano-array on material structure is a novel and high-efficient strategy to design catalysts,however,it still remains a challenge to fabricate unique nano-architecture electrocatalyst with prominent activity and superior durability for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER).Herein,a unique nano-architecture catalyst is successfully synthesized by using NiFe LDH nanosheets as framework to the in situ growth Mo-doped Ni2P ultrafine nanosheets (marked as Mo-Ni2P@NiFe LDH/NF).The unique 3D core-shell nano-architecture is favorable for enhancing electron transfer/mass diffusion,providing abundant active sites,prompting O2/H2 gas release,and creating the synergistic effect between Mo-Ni2P and NiFe LDH.Therefore,comparing with pure NiFe LDH/NF and Mo-Ni2P/NF electrodes,walnut-like Mo-Ni2P@NiFe LDH/NF catalyst exhibits significantly improved electrocatalytic activities and durability towards OER (269 mV@40 mA cm-2),HER (82 mV@10 mA cm-2),and overall water splitting (1.46 V@10 mA cm-2),respectively.Such electrocatalytic activity of Mo-Ni2P@NiFe LDH/NF is comparable with that of majority reported non-precious metal catalysts and even precious catalysts (IrO2 and Pt/C).This work presents a new perspective strategy to fabricate ingeniously bifunctional electrocatalysts with well-designed structure and superior performance for clean energy conversion technologies or storage devices.

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All-climate aqueous supercapacitor enabled by a deep eutectic solvent electrolyte based on salt hydrate Xudong Bu, Yurong Zhang, Yinglun Sun, Lijun Su, Jianing Meng, Xionggang Lu, Xingbin Yan 2020, 49(10): 198-204.  DOI: 10.1016/j.jechem.2020.02.042 摘要 ( 28 )   Aqueous supercapacitors (SCs) have received considerable attention owing to the utilization of low-cost,non-flammable,and low-toxicity aqueous electrolytes thus could eliminate the safety and cost concerns,but their wide temperature range applications have generally suffered from frozen of electrolyte and insufficient ionic conductivity at low temperatures.Herein,we demonstrate the feasibility of using an unconventional Deep Eutectic Solvent (DES) based on H2O-Mg(ClO4)2·6H2O binary system as electrolyte to construct all-climate aqueous carbon-based SC.This unconventional class DES completely base on inorganic substances and achieving simply mix inexpensive salts and water together at the right proportions.Attributed to the attractive feature of extremely low freeze temperature of -69℃,this electrolyte can enable the 1.8 V carbon-based SC to fully work at -40℃ with outstanding cycling stability.This DES electrolyte comprising of a single salt and a single solvent without any additive will open up an avenue for developing simple and green electrolytes to construct all-climate SC.

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Exploiting quasi-one-dimensional confinement for proficient hydrogen production from formic acid at room temperature Tao Jiang, Peng Lu, Meng-Jiao Xu, Jian-Dong Lin, Yong-Mei Liu, Yong Cao, He-Yong He 2020, 49(10): 205-213.  DOI: 10.1016/j.jechem.2020.02.040 摘要 ( 9 )   We describe herein that the quasi-one-dimensional confinement effect of functionalized nanoporous supports is particularly advantageous for boosting formic acid (FA) dehydrogenation efficiency over palladium nanoparticles (NPs).Benefiting from their unique structural merits that lead to significant lowering of the entropic barrier for FA activation,the Pd NPs interiorly located on the amino-modified MCM-41 offer the promise of more than an order of magnitude speedup of the initial activity in H2 production from FA over their exterior analogs.Under mild and additive-free conditions,ultrafine Pd NPs confined in aminomodified MCM-41 channels exhibit an initial turnover frequency as high as 46,677 h-1 and a turnover number up to 1,060,000 at 60℃.In conjunction with the enhancement and robust performance for efficient regeneration of FA via CO2 hydrogenation,the presented approach greatly contributes to the development of FA-based hydrogen storage and related technologies as viable means of enabling sustainable future energy prospects.

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Supramolecular electrostatic self-assembly of mesoporous thin-walled graphitic carbon nitride microtubes for highly efficient visible-light photocatalytic activities Yilin Chen, Xingchen He, Dongsheng Guo, Yanqin Cai, Jingling Chen, Yun Zheng, Bifen Gao, Bizhou Lin 2020, 49(10): 214-223.  DOI: 10.1016/j.jechem.2020.02.035 摘要 ( 5 )   For efficient solar energy conversion,the morphology engineering of hollow graphitic carbon nitride (g-C3N4) is one of the promising approachs benefiting from abundant exposed active sites and short photocarrier transport distances,but is difficult to control on account of easy structural collapse.Herein,a facile supramolecular electrostatic self-assembly strategy has been developed for the first time to fabricate mesoporous thin-walled g-C3N4 microtubes (mtw-CNT) with shell thickness of ca.13 nm.The morphological control of g-C3N4 enhances specific surface area by 12 times,induces stronger optical absorption,widens bandgap by 0.18 eV,improves photocurrent density by 2.5 times,and prolongs lifetimes of charge carriers from bulk to surface,compared with those of bulk g-C3N4.As a consequence,the transformed g-C3N4 exhibits the optimum photocatalytic H2-production rate of 3.99 mmol·h-1·g-1 (λ >420 nm) with remarkable apparent quantum efficiency of 8.7% (λ=420 ±15 nm) and long-term stability.Moreover,mtw-CNT also achieves high photocatalytic CO2-to-CO selectivity of 96% (λ >420 nm),much better than those on the most previously reported porous g-C3N4 photocatalysts prepared by the conventional hard-templating and soft-templating methods.

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Boosting the electrochemical performance and reliability of conducting polymer microelectrode via intermediate graphene for on-chip asymmetric micro-supercapacitor Muhammad Tahir, Liang He, Wei Yang, Xufeng Hong, Waqas Ali Haider, Hui Tang, Zhe Zhu, Kwadwo Asare Owusu, Liqiang Mai 2020, 49(10): 224-232.  DOI: 10.1016/j.jechem.2020.02.036 摘要 ( 9 )   High-performance anode is hurdle for on-chip planar microsupercapacitor (MSC).Polypyrrole (PPy) is a highly attractive pseudocapacitive material,but its low cycling stability,and low adhesion with current collector hinder its practicability.Herein we propose one-prong generic strategy to boost the cycling stability of PPy.For our strategy,the electrochemical deposition of multilayered reduced graphene oxide (rGO) on micropatterned Au is utilized,and the resultant rGO@Au pattern is then used for growing highly porous PPy nanostructures by facile electrochemical polymerization.The fabricated PPy anode on rGO@Au has quasi rectangular cyclic voltammetry curves up to -0.7 V and exceptional cycling stability,retaining 82% of capacitance after 10,000 charge/discharge cycles in 2 M KCl electrolyte.The outstanding reliability of PPy on rGO@Au is due to the flexibility of rGO,accommodating structural pulverization and providing a promising background for the nucleation of highly porous nanostructure.Further,an all-polymer based asymmetric aqueous MSC (AMSC) is constructed with PPy anode and PEDOT cathode,which exhibited excellent electrochemical performance compared with conventional symmetric MSCs based on conducting polymers.The constructed AMSC delivered a maximum areal capacitance of 15.9 mF cm-2 (99.3 F cm-3),high specific energy and power densities of 4.3 μWh cm-2 (27.03 mWh cm-3) and 0.36 W cm-2 (0.68 W cm-3) at 1.4 V,respectively.The enhanced electrochemical performances can be illustrated by nucleation mechanism,in which surface topology of rGO generates a promising background for nucleation and electrochemical growth of nanoporous pseudocapacitive conducting polymers with superior interfacial contact and improved surface area.

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Exfoliated multi-layered graphene anode with the broadened delithiation voltage plateau below 0.5 V Xinlong Ma, Xinyu Song, Yushu Tang, Enzuo Liu, Chenggen Xu, Chuanlei Qi, Yun Li, Jinsen Gao, Yongfeng Li 2020, 49(10): 233-242.  DOI: 10.1016/j.jechem.2020.02.044 摘要 ( 8 )   The commercial graphite (CG) is the conventional anode material for lithium ion batteries (LIBs) due to its low delithiation voltage plateau (below 0.5 V) and extraordinary durability.Nevertheless,the further promotion of energy density of LIBs is restricted by the limited capacity below 0.5 V of CG.Here,based on the supercritical CO2 exfoliation technique,the production of multi-layered graphene (MLG) is achieved from the pilot scale production line.The great merit of the exfoliated MLG anode is that the voltage plateau below 0.5 V is broadened obviously as compared to those of natural graphite and CG.Additionally,no obvious lithium dendrites are observed for MLG during the lithiation process.The large delithiation capacity under the low voltage plateau of MLG is mainly benefited from the combination of Li intercalation and boundary storage mechanism,which is further confirmed by the density functional theory calculations.The LiFePO4/MLG full cell can afford the satisfactory electrochemical property with respect to the capacity,energy density and ultralong cycling stability (90% capacity retention after 500 cycles at 2 C),significantly better than that of LiFePO4/CG.Besides,this developed technique not only dedicates to producing the high-performance anode for LIBs but also opens a door for the mass production of MLG in the industrial scale.

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Pyrazine-nitrogen-rich exfoliated C4N nanosheets as efficient metal-free polymeric catalysts for oxygen reduction reaction Yuan Li, Chunshao Mo, Jing Li, Dingshan Yu 2020, 49(10): 243-247.  DOI: 10.1016/j.jechem.2020.02.046 摘要 ( 4 )   Herein,we for the first time demonstrate the synthesis of exfoliated C4N nanosheets via a top-down approach and exploit their use as a new class of organic polymeric catalyst for the oxygen reduction reaction (ORR).The obtained C4N nanosheets are semi-conductive with a small band gap of 1.41 eV and contain abundant pyrazine-nitrogen moieties uniformly distributed throughout C4N.Density function theory calculations reveal that the intramolecular charge transfer induced by pyrazine-nitrogen in C4N enables effective charge redistribution to activate the conjugated structure and facilitate the oxygen adsorption,while the exfoliated sheet-like C4N formation renders improved electrochemical active surface area and results in high exposure of active sites.As a result,despite the bulk C4N is not active,the sheet-like C4N yield markedly improved ORR performance,even on a par with the commercial Pt/C catalyst.Our recent findings not only enrich the family members of two-dimensional conjugated polymer nanosheets but also open up new opportunity to explore new metal-free organic polymeric materials for efficient oxygen reduction catalysis and beyond.

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Interface tuning of Cu+/Cu0 by zirconia for dimethyl oxalate hydrogenation to ethylene glycol over Cu/SiO2 catalyst Yujun Zhao, Huanhuan Zhang, Yuxi Xu, Shengnian Wang, Yan Xu, Shengping Wang, Xinbin Ma 2020, 49(10): 248-256.  DOI: 10.1016/j.jechem.2020.02.038 摘要 ( 11 )   An efficient ZrO2-doped Cu/SiO2 catalyst was fabricated through hydrolysis precipitation method (HP) and used to produce ethylene glycol (EG) through dimethyl oxalate (DMO) hydrogenation.The states for zirconia on copper catalyst and roles in DMO hydrogenation were investigated through various characterization tools,including N2 physical adsorption,XRD,H2-TPR,Methyl glycolate-TPD-MS,XPS,XAES as well.Compared with common ammonia evaporation and co-precipitation methods used in catalyst preparation,this HP method is found to effectively suppress the agglomeration and further size growth of copper nanoparticles by enhancing the interactions between copper and zirconia species.More importantly,uniform distribution of ZrO2 dopant is achieved due to the pseudo-homogeneous reactions in the mixing step of catalyst preparation.A proper amount of zirconium dopant helps achieve the desirable proportion of Cu+/(Cu++Cu0) for surface copper species,especially promotes the production of Cu+ species originated from Cu-ZrO2 species at the interface of copper and zirconia particles.In comparison with Cu+ species formed from copper phyllosilicates reduction,the Cu+ sites derived from Cu-ZrO2 species show higher adsorption ability of MG,an important intermediate species in ethylene glycol production.These adsorbed MG molecules further react with atomic hydrogen shifted from adjacent metallic copper surface,leading to a higher catalytic behavior.For the EG production via DMO hydrogenation,the turnover frequency (TOF) normalized by Cu0 species on CuZr/SiO2 catalyst is 1.8 times than that of traditional Cu/SiO2 counterpart.Due to the enhanced synergy effect between Cu+ and Cu0 active sites,a lower activation energy of ester hydrogenation on this ZrO2-doped Cu/SiO2 catalyst is believed to be responsible for the significant improvement.

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Deciphering pitting behavior of lithium metal anodes in lithium sulfur batteries Fanyang Huang, Shuai Wang, Yulin Jie, Evan Hansen, Shiyang Wang, Zhanwu Lei, Jian Liu, Ruiguo Cao, Genqiang Zhang, Shuhong Jiao 2020, 49(10): 257-261.  DOI: 10.1016/j.jechem.2020.02.039 摘要 ( 9 )   Unambiguous understanding in lithium anode failure mechanism calls for a comprehensive methodology to investigate the coupled morphological,electrochemical and mechanical behaviors during the stripping process.In this work,a mechanistic investigation of the pitting behavior of lithium metal in an electrolyte containing lithium polysulfides in lithium sulfur batteries was developed.It is found that lithium polysulfides could aggravate the nonuniform stripping of lithium electrodes.

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Vertically aligned one-dimensional ZnO/V2O5 core-shell hetero-nanostructure for photoelectrochemical water splitting Tian-Feng Hou, Muhammad Ali Johar, Ramireddy Boppella, Mostafa Afifi Hassan, Swati J.Patil, Sang-Wan Ryu, Dong-Weon Lee 2020, 49(10): 262-274.  DOI: 10.1016/j.jechem.2020.02.004 摘要 ( 23 )   The vertically aligned one-dimensional (1D) core-shell structure can maximize the exposure and use of the functionally active surface while maintaining the geometric effects caused by the underlying structure.Herein,we have fabricated 1D vertically aligned ZnO/V2O5 core-shell hetero-nanostructure nanorod arrays (NRs) for photoelectrochemical (PEC) water splitting.ZnO/V2O5 NRs were prepared through the hydrothermal growing of ZnO NRs and then radio frequency (RF) magnetron sputtering deposition of V2O5 for 300,600 and 900 s.The photocurrent density of ZnO/V2O5-based photoanodes was gradually increased with the sputtering time,reaching the maximum value of 1.21 mA/cm2 at 1.23 V vs.reversible hydrogen electrode (RHE) for ZnO/V2O5-600,whereas for pure ZnO-based photoanode was 0.42 mA/cm2.The incident photon to electron conversion efficiency (IPCE) of ZnO/V2O5-600 evaluated to be 82.3% which was 2.3 times higher than that of ZnO (36.4%).The improved PEC performance of ZnO/V2O5-600 is because the core-shell structure with a moderate thickness of the V2O5 layer has the extremely high carrier density,largest electrochemically active surface area (ECSA),largest carrier density,lowest charge recombination rate,and the longest lifetime of e-h pairs due to the formation of the staggered gap junction.This study provides an effective way to design and fabrication of hetero-nanostructures for highefficiency photoelectrodes.

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Ultrafine Pt nanoparticles supported on double-shelled C/TiO2 hollow spheres material as highly efficient methanol oxidation catalysts Xiaoyu Yue, Yuguang Pu, Wen Zhang, Ting Zhang, Wei Gao 2020, 49(10): 275-282.  DOI: 10.1016/j.jechem.2020.02.045 摘要 ( 7 )   Catalyst support is extremely important for future fuel cell devices.In this work,we developed doubleshelled C/TiO2 (DSCT) hollow spheres as an excellent catalyst support via a template-directed method.The combination of hollow structure,TiO2 shell and carbon layer results in excellent electron conductivity,electrocatalytic activity,and chemical stability.These uniformed DSCT hollow spheres are used as catalyst support to synthesize Pt/DSCT hollow spheres electrocatalyst.The resulting Pt/DSCT hollow spheres exhibited high catalytic performance with a current density of 462 mA mg-1 for methanol oxidation reaction,which is 2.52 times higher than that of the commercial Pt/C.Furthermore,the increased tolerance to carbonaceous poisoning with a higher If/Ib ratio and a better long-term stability in acid media suggests that the DSCT hollow sphere is a promising C/TiO2-based catalyst support for direct methanol fuel cells applications.

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Pyrolysis-free formamide-derived N-doped carbon supporting atomically dispersed cobalt as high-performance bifunctional oxygen electrocatalyst Yin Jia, Yiyan Wang, Guoxin Zhang, Cong Zhang, Kai Sun, Xuya Xiong, Junfeng Liu, Xiaoming Sun 2020, 49(10): 283-290.  DOI: 10.1016/j.jechem.2020.01.034 摘要 ( 8 )   Non-precious metal-nitrogen-carbon (MNC) electrocatalysts have gained tremendous attention as promising electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER).However,the most applicable strategies for the synthesis of MNC materials heavily rely on pyrolysis treatment,which may easily lead to metal aggregation and subsequent degradation of catalytic performance.Herein,we developed a pyrolysis-free strategy for preparing MNC materials,which was demonstrated by achieving ultrathin cobalt-nitrogen-carbon (CoNC) layer with dense atomically dispersed cobalt sites depositing on graphene oxide (GO) via simple treatment of Co salt and GO in formamide.The formamide-derived CoNC layer deposited on GO (termed as f-CoNC/GO) could be controlled in 1-2 nm thick.Remarkably,the f-CoNC/GO composite without pyrolysis exhibited excellent bifunctional performance toward ORR and OER,which was attributed to the dense atomically dispersed Co-Nx sites and improved conductivity by GO substrate.Furthermore,the f-CoNC/GO-assembled rechargeable Zn-air battery showed highly efficient and stable performance,demonstrating our pyrolysis-free method to be straightforward,cost-effective,and feasible for the scalable production of MNC electrocatalysts.

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Iridic oxide nanoparticles grown in situ on BCN nanotubes as highly efficient dual electrocatalyst for rechargeable lithium-O2 batteries Xufang Li, Yajun Zhao, Jing Zhang, Chaoxiong Li, Shan Wu, Qiufan Shi, Dawei Zhang, Qingchun Yang 2020, 49(10): 291-298.  DOI: 10.1016/j.jechem.2020.02.048 摘要 ( 5 )   Oxygen cathode catalysts can significantly address the issues faced by Li-O2 battery.In this research,a composite of IrO2 nanoparticles grown in situ on BCN nanotubes (IrO2@BCNNTs) has been synthesized by facile hydrothermal method,which is initially fabricated as cathode catalyst for Li-O2 battery.The results indicate that IrO2@BCNNTs nanocomposite has a better effect on improving the actual discharge capacity,voltage gap and cyclability of Li-O2 battery.In addition,it is also demonstrated that the IrO2@BCNNTs composite exhibits bifunctional characteristics for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through rotating disk electrode (RDE) measurements.The excellent performances of the synthesized catalyst may be attributed to the unique interconnected tubular structure and strong synergistic effect,which can provide more charged sites and defect sites and then facilitate reversible Li2O2 formation and decomposition.Therefore,it is promising for applying the rational design of the bifunctional catalyst to Li-O2 battery.

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Ultrasensitive and stable X-ray detection using zero-dimensional lead-free perovskites Xiaojia Zheng, Wei Zhao, Peng Wang, Hairen Tan, Makhsud I.Saidaminov, Shujie Tie, Ligao Chen, Yufei Peng, Jidong Long, Wen-Hua Zhang 2020, 49(10): 299-306.  DOI: 10.1016/j.jechem.2020.02.049 摘要 ( 31 )   Sensitive and reliable X-ray detectors are essential for medical radiography,industrial inspection and security screening.Lowering the radiation dose allows reduced health risks and increased frequency and fidelity of diagnostic technologies for earlier detection of disease and its recurrence.Three-dimensional (3D) organic-inorganic hybrid lead halide perovskites are promising for direct X-ray detection-they show improved sensitivity compared to conventional X-ray detectors.However,their high and unstable dark current,caused by ion migration and high dark carrier concentration in the 3D hybrid perovskites,limits their performance and long-term operation stability.Here we report ultrasensitive,stable X-ray detectors made using zero-dimensional (0D) methylammonium bismuth iodide perovskite (MA3Bi2I9) single crystals.The 0D crystal structure leads to a high activation energy (Ea) for ion migration (0.46 eV) and is also accompanied by a low dark carrier concentration (~106 cm-3).The X-ray detectors exhibit sensitivity of 10,620 μC Gyair-1 cm-2,a limit of detection (LoD) of 0.62 nGyair s-1,and stable operation even under high applied biases;no deterioration in detection performance was observed following sensing of an integrated X-ray irradiation dose of ~23,800 mGyair,equivalent to >200,000 times the dose required for a single commercial X-ray chest radiograph.Regulating the ion migration channels and decreasing the dark carrier concentration in perovskites provide routes for stable and ultrasensitive X-ray detectors.

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3D hierarchical microspheres constructed by ultrathin MoS2-C nanosheets as high-performance anode material for sodium-ion batteries Wenlong Zhang, Haihui Zhou, Zhongyuan Huang, Songlin Li, Chuqing Wang, Huanxin Li, Zhanheng Yan, Teng Hou, Yafei Kuang 2020, 49(10): 307-315.  DOI: 10.1016/j.jechem.2020.03.001 摘要 ( 15 )   MoS2/C composites are considered to have great application potential in sodium-ion batteries (SIBs).It is a challenging and meaningful subject that developing high-performance anode materials via combining MoS2 and carbon effectively to give free rein to their advantages in sodium ion storage.In this work,a novel MoS2-C material was designed by using cellulose nanocrystals (CNCs) as low-cost and green carbon source.3D hierarchical microspheres (200-250 nm) constructed by ultrathin MoS2-C nanosheets were synthesized by synchronizing the pre-carbonization of CNCs with the formation of MoS2 in hydrothermal reaction and subsequent pyrolysis process.It is found that the ultrathin MoS2-C nanosheets were composed of CNCs-derived short-range ordered carbon and few-layered MoS2.Benefiting from the unique structure and robust combination of MoS2 and CNCs-derived carbon,the ultrathin MoS2-C nanosheets composite was proved to have excellent cycling stability and superior rate performance in sodium-ion half-cell test and have high first reversible specific capacity of 397.9 mAh/g in full-cell test.This work provides a significant and effective pathway to prepare MoS2-C materials with excellent electrochemical performance for the application in large-scale energy storage systems.

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In-situ assembly of TiO2 with high exposure of (001) facets on three-dimensional porous graphene aerogel for lithium-sulfur battery Ming Wang, Shunyuan Tan, Shuting Kan, Yufeng Wu, Shangbin Sang, Kaiyu Liu, Hongtao Liu 2020, 49(10): 316-322.  DOI: 10.1016/j.jechem.2020.03.011 摘要 ( 4 )   Resulting from the development of electric vehicles,high energy-density Li-S batteries have recently attracted ever-increasing attentions worldwide.However,continuous dissolution of cathodic sulfur and followed shuttle effect of polysulfides lead to very limited service lifetime for currently-applied Li-S batteries.Herein,a 3D porous graphene aerogel (GA) decorated with high exposure of anatase TiO2(001) nanoplatelets is proposed as robust host to immobilize cathodic sulfur.Compared with commonly used TiO2(101) nanoparticles,the TiO2(001) nanoplatelets have highly matched lattices with graphene (002) nanosheets,thus facilitating the electronic transfer.The in-site assembled TiO2@GA host exhibits superior sulfur-immobilized capability,which cannot only entrap sulfur by physical confinement,but also capture dissoluble sulfurous species by chemical bonding.The fabricated S@TiO2@GA cathode shows excellent electrochemical performance with high discharge capacity,superior rate capability,and durable cycling stability as well,supposed to be a promising cathode for high-performance Li-S battery applications.

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Oxygen reduction reaction on single Pt nanoparticle Zhi-Peng Xiang, Ai-Dong Tan, Zhi-Yong Fu, Jin-Hua Piao, Zhen-Xing Liang 2020, 49(10): 323-326.  DOI: 10.1016/j.jechem.2020.02.051 摘要 ( 13 )   Nanocollision electrochemistry is employed to evaluate the ORR's activity of one single Pt nanoparticle,the effect of the size and ligand is investigated.The size-normalized activity of the Pt nanoparticle of 4 nm is two times higher than that of 25 nm,confirming that the intrinsic activity does depend on the size of the nanoparticles.It is further found that the adsorbed ligand does yield effect on electrocatalysis,and the adsorption strength follows the order of PVP > CTAB > citrate.This work is of significance to understand the nature of the ORR's electrocatalysis at the level of an individual entity,which makes the structure-activity correlation in a more reliable way.

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Nitrogen doping and graphitization tuning coupled hard carbon for superior potassium-ion storage Junxian Hu, Yangyang Xie, Meng Yin, Zhian Zhang 2020, 49(10): 327-334.  DOI: 10.1016/j.jechem.2020.03.005 摘要 ( 12 )   Hard carbon material is one of the most promising anode materials for potassium ion batteries (PIBs) due to its distinct disordered and non-expandable framework.However,the intrinsically disordered microarchitecture of hard carbon results in low electric conductivity and poor rate capability.Herein,nitrogendoped and partially graphitized hard carbons (NGHCs) derived from commercial coordination compound precursor-ethylenediaminetetraacetic acid (EDTA) disodium cobalt salt hydrate are designed and prepared as high-performance PIBs anode materials.By means of a facile annealing method,nitrogen elements and graphitic domains can be controllably introduced to NGHCs.The resulting NGHCs show structural merits of mesoporous construction,nitrogen doping and homogeneous graphitic domains,which ensures fast kinetics and electron transportation.Applying in anode for PIBs,NGHCs exhibit robust rate capability with high reversible capacity of 298.8 mAh g-1 at 50 mA g-1,and stable cycle stability of 137.6 mAh g-1 at 500 mA g-1 after 1000 cycles.Moreover,the ex situ Raman spectra reveal a mixture "adsorption-intercalation mechanism" for potassium storage of NGHCs.More importantly,full PIBs by pairing with perylenetetracarboxylic dianhydride (PTCDA) cathode demonstrate the promising potential of practical application.In terms of commercial precursor,facile synthesis and long cycle lifespan,NGHCs represent a brilliant prospect for practical large-scale applications.

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The influence of formation temperature on the solid electrolyte interphase of graphite in lithium ion batteries Chong Yan, Yu-Xing Yao, Wen-Long Cai, Lei Xu, Stefan Kaskel, Ho Seok Park, Jia-Qi Huang 2020, 49(10): 335-338.  DOI: 10.1016/j.jechem.2020.02.052 摘要 ( 100 )   Lithium-ion battery has greatly changed our lifestyle and the solid electrolyte interphase (SEI) covered on the graphite anode determines the service life of a battery.The formation method and the formation temperature at initial cycle of a battery determine the feature of the SEI.Herein,we investigate the gap of formation behavior in both a half cell (graphite matches with lithium anode) and a full cell (graphite matches with NCM,short for LiNixCoyMn1-x-yO2) at different temperatures.We conclude that high temperature causes severe side reactions and low temperature will result in low ionic conductive SEI layer,the interface formed at room temperature owns the best ionic conductivity and stability.

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FeCo alloy catalysts promoting polysulfide conversion for advanced lithium-sulfur batteries Hongyi Li, Linfeng Fei, Rong Zhang, Shenglan Yu, Yongyi Zhang, Longlong Shu, Yong Li, Yu Wang 2020, 49(10): 339-347.  DOI: 10.1016/j.jechem.2020.02.050 摘要 ( 10 )   Lithium sulfur batteries (LSBs) draw extensive interest because of the ultra-high capacity and low material cost.However,the sluggish lithium polysulfides (LIPSs) conversion processes are detrimental to cycle stability and rate capability,inhibiting the commercial application of LSBs.Here we present the well-designed FeCo alloy catalysts anchored on porous carbon (FeCo-C) as sulfur host to improve the electrochemical performance by accelerating the conversion reactions.The FeCo alloy demonstrates high catalytic effect and strong adsorption capability of LIPSs,in which potential polarization can be greatly decreased and "shuttle effects" can be largely avoided.As a result,the obtained S/FeCo-C composites show an initial specific capacity of 791.9 mAh g-1 at a large current density of 2 C and maintain 502.5 mAh g-1 even after 500 cycles.Moreover,720 mAh g-1 (corresponding to 70% retention) can be achieved after 100 cycles at 0.2 C with a high sulfur content of 80 wt%,enabling high sulfur utilization.This work not only provides a new insight to investigate the conversion kinetics of LiPSs,but also opens up a new avenue for advanced lithium sulfur batteries.

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Controllable fabrication of nitrogen-doped porous nanocarbons for high-performance supercapacitors via supramolecular modulation strategy Huaxia Chen, Xingyu Lu, Haihua Wang, Dianpeng Sui, Fanbao Meng, Wei Qi 2020, 49(10): 348-357.  DOI: 10.1016/j.jechem.2020.02.043 摘要 ( 6 )   In the present work,we developed a micellar system of milk protein-surfactant (SDS)-graphene to prepare the graphene-based aerogels via hydrothermal and freeze-drying method,in which the novel surface-property of aerogels can be tuned with the decreasing of micellar size in the colloid systems resulting the improved specific surface area.The milk protein also severed as green and sustainable sources to introduce nitrogen heteroatoms into the aerogels.Subsequently,the aerogels were further graphitized and activated to fabricate N-doped porous nanocarbon at 600℃.The initial surface composition and structure of the aerogel,which was proved,has obvious impact on the final structure of the synthesized nanocarbon materials,and thus influence their electrochemical activity.The optimized nanocarbon materials (MGPC-5),with enhanced specific surface area,degree of graphitization,and nitrogen doping,exhibited excellent capacitance performance and stability in both three-electrode system (518.8 F/g at a current density of 0.1 A/g) and symmetrical electrode system (120.8 F/g at current density of 0.1 A/g and with ~95% capacitance retention after 5000 cycles of charging and discharging at 3 A/g) in KOH.The assembled supercapacitor also shows ideal capacitive properties in series and parallel configurations.Tested with a stable 1.6 V windows in Li2SO4 electrolyte,the symmetric supercapacitor cell exhibits a high energy density up to 36.7 W h/kg.The present work provides a feasible fabrication method for high-performance supercapacitor based on graphene and biomass derived carbon,the proposed surfaceproperty regulation and supercapacitor performance improvement strategy may also shed light on other energy related materials or system.

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K+ alkalization promoted Ca2+ intercalation in V2CTx MXene for enhanced Li storage Ming Lu, Yaopeng Zhang, Junnan Chen, Wenjuan Han, Wei Zhang, Haibo Li, Xia Zhang, Bingsen Zhang 2020, 49(10): 358-364.  DOI: 10.1016/j.jechem.2020.03.002 摘要 ( 13 )   Although MXenes is highly attractive as anode materials of lithium ion batteries,it sets a bottleneck for higher capacity of the V2CTx MXene due to the limited interlayer space and the derived surface terminations.Herein,the cation intercalation and ion-exchange were well employed to achieve a K+ and Ca2+ intercalated V2CTx MXene.A larger interlayer distance and low F surface terminations were thereof obtained,which accelerates the ion transport and promotes the delicate surface of V2CTx MXene.As a result,a package of enhanced capacity,rate performance and cyclability can be achieved.Furthermore,the ion exchange approach can be extended to other 2D layered materials,and both the interlayer control and the surface modification will be achieved.

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Electrochemical exfoliation of two-dimensional layered black phosphorus and applications Le Li, Dan Zhang, Jianping Deng, Yuchun Gou, Junfei Fang 2020, 49(10): 365-374.  DOI: 10.1016/j.jechem.2020.03.010 摘要 ( 8 )   With the discovery of graphene,black phosphorus (BP) has been rediscovered as a two-dimensional (2D) layered material.Since its first preparation in 2014,2D BP has elicited immense interest,and has exhibited excellent properties,such as distinct pleated structures in layers,adjustable direct bandgap,high carrier mobility,moderate on/off ratio,large specific surface area,and various interesting in-layer anisotropies.However,the realization of these excellent properties depends on the preparation of highquality 2D BP sheets.Electrochemical exfoliation methods are typically performed under mild conditions,thus,these methods are convenient,controllable,and can produce high-quality 2D BP sheets.This review summarizes research progress in BP sheets preparation through anodic,cathodic,and electrolyte exfoliation in recent years.Different exfoliating methods affect the quality of 2D BP sheets.Moreover,possible exfoliating mechanisms and the potential applications of different exfoliating methods are summarized and discussed in detail.Lastly,the shortcomings of existing research on electrochemical exfoliation are presented,and suggestions and prospects for future research on the electrochemical exfoliation of 2D BP are proposed.

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Hybrid battery integrated by Zn-air and Zn-Co3O4 batteries at cell level Ning Liu, Honglu Hu, Xinxin Xu, Qiang Wang 2020, 49(10): 375-383.  DOI: 10.1016/j.jechem.2020.02.037 摘要 ( 11 )   The construction of Zn based hybrid battery through the combination of Zn-air and Zn-Co3O4 batteries at cell level is a feasible strategy to integrate high voltage,specific capacity and energy density in one power supply equipment.For Zn based hybrid battery,an efficient cathode material with high specific capacitance and excellent ORR,OER activities is a vital component,which determines its performance in great extent.In this work,with Co based coordination polymer as precursor,oxygen vacancy-rich Co3O4 based cathode material is synthesized.In this material Co3O4 particles with the size about 20 to 35 nm reside evenly in mesoporous carbon matrix doped by nitrogen atoms.In OER,the overpotential of this cathode material is merely 330 mV.Its ORR proceeds with a typical four electron process with half wave achieving 0.76 V.If charge/discharge at 1 A·g-1,specific capacitance of this cathode material is 254.4 mAh·g-1.As current density increases to 20 A·g-1,the specific capacitance still arrives at 122.5 mAh·g-1 with nearly 50% retained.Based on attractive performance of this cathode material,Zn based hybrid battery is assembled.When discharge at 1 mA·cm-2,it presences two voltage platforms at 1.71 and 1.14 V.In this situation,specific capacitance reaches 790 mAh·g-1 with energy density 928 Wh·kg-1.Hybrid battery shows promising stability after 300-cycle continuous test.