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2020, Vol. 46, No. 7　Online: 2020-07-15

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Tuning the selectivity of photoreduction of CO2 to syngas over Pd/layered double hydroxide nanosheets under visible light up to 600 nm Xian Wang, Zelin Wang, Ya Bai, Ling Tan, Yanqi Xu, Xiaojie Hao, Jikang Wang, Abdul Hanif Mahadi, Yufei Zhao, Lirong Zheng, Yu-Fei Song 2020, 46(7): 1-7.  DOI: 10.1016/j.jechem.2019.10.004 摘要 ( 5 )   Photocatalytic reduction of CO2 with H2O to syngas is an effective way for producing high value-added chemical feedstocks such as methanol and light olefins in industry.Nevertheless,the precise control of CO/H2 ratio from photocatalytic CO2 reduction reaction still poses a great challenge for the further application.Herein,we prepared a series of highly efficient heterostructure based on highly dispersed palladium supported on ultrathin CoAl-layered double hydroxide (LDH).In conjunction with a Ru-complex sensitizer,the molar ratios of CO/H2 can be tuned from 1:0.74 to 1:3 under visible-light irradiation (λ> 400 nm).More interestingly,the syngas can be obtained under light irradiation at λ > 600 nm.Structure characterization and density functional theory calculations revealed that the remarkable catalytic activity can be due to the supported palladium,which improved the charge transfer efficiency.Meanwhile,more H atoms were used to generate H2 on the supported palladium for further tunable CO/H2 ratio.This work demonstrates a new strategy for harnessing abundant solar-energy to produce syngas from a CO2 feedstock.

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Efficient and stable planar all-inorganic perovskite solar cells based on high-quality CsPbBr3 films with controllable morphology Xiaojing Wan, Ze Yu, Wenming Tian, Fuzhi Huang, Shengye Jin, Xichuan Yang, Yi-Bing Cheng, Anders Hagfeldt, Licheng Sun 2020, 46(7): 8-15.  DOI: 10.1016/j.jechem.2019.10.017 摘要 ( 4 )   All-inorganic cesium lead bromide (CsPbBr3) perovskite is attracting growing interest as functional materials in photovoltaics and other optoelectronic devices due to its superb stability.However,the fabrication of high-quality CsPbBr3 films still remains a big challenge by solution-process because of the low solubility of the cesium precursor in common solvents.Herein,we report a facile solution-processed approach to prepare high-quality CsPbBr3 perovskite films via a two-step spin-coating method,in which the CsBr methanol/H2O mixed solvent solution is spin-coated onto the lead bromide films,followed by an isopropanol-assisted post-treatment to regulate the crystallization process and to control the film morphology.In this fashion,dense and uniform CsPbBr3 films are obtained consisting of large crystalline domains with sizes up to microns and low defect density.The effectiveness of the resulting CsPbBr3 films is further examined in perovskite solar cells (PSCs) with a simplified planar architecture of fluorine-doped tin oxide/compact TiO2/CsPbBr3/carbon,which deliver a maximum power conversion efficiency of 8.11% together with excellent thermal and humidity stability.The present work offers a simple and effective strategy in fabrication of high-quality CsPbBr3 films for efficient and stable PSCs as well as other optoelectronic devices.

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Effect of BaNH,CaNH,Mg3N2 on the activity of Co in NH3 decomposition catalysis Pei Yu, Han Wu, Jianping Guo, Peikun Wang, Fei Chang, Wenbo Gao, Weijin Zhang, Lin Liu, Ping Chen 2020, 46(7): 16-21.  DOI: 10.1016/j.jechem.2019.10.014 摘要 ( 6 )   Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost.In this work,we examined the effect of BaNH,CaNH and Mg3N2 on the catalytic activity of Co in the NH3 decomposition reaction.The H2 formation rate ranks the order as Co-BaNH > Co-CaNH > Co-Mg3N2 ≈ Co/CNTs within a reaction temperature range of 300-550 ℃.It is worth pointing out that the H2 formation rate of Co-BaNH at 500 ℃ reaches 20 mmolH2 gcat-1 min-1,which is comparable to those of the active Ru/Al2O3 (ca.17 mmolH2 gcat-1 min-1) and Ru/AC (21 mmolH2 gcat-1 min-1) catalysts under the similar reaction conditions.In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea (46.2 kJ mol-1) than other Co-based catalysts,suggesting that BaNH may play a different role from CaNH,Mg3N2 and CNTs during the catalytic process.Combined results of XRD,Ar-TPD and XAS show that a [Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH,which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.

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Three-dimensionally interconnected Co9S8/MWCNTs composite cathode host for lithium-sulfur batteries Shengyu Zhao, Xiaohui Tian, Yingke Zhou, Ben Ma, Angulakshmi Natarajan 2020, 46(7): 22-29.  DOI: 10.1016/j.jechem.2019.10.011 摘要 ( 2 )   Several challenging issues,such as the poor conductivity of sulfur,shuttle effects,large volume change of cathode,and the dendritic lithium in anode,have led to the low utilization of sulfur and hampered the commercialization of lithium-sulfur batteries.In this study,a novel three-dimensionally interconnected network structure comprising Co9S8 and multiwalled carbon nanotubes (MWCNTs) was synthesized by a solvothermal route and used as the sulfur host.The assembled batteries delivered a specific capacity of 1154 mAh g-1 at 0.1 C,and the retention was 64% after 400 cycles at 0.5 C.The polar and catalytic Co9S8 nanoparticles have a strong adsorbent effect for polysulfide,which can effectively reduce the shuttling effect.Meanwhile,the three-dimensionally interconnected CNT networks improve the overall conductivity and increase the contact with the electrolyte,thus enhancing the transport of electrons and Li ions.Polysulfide adsorption is greatly increased with the synergistic effect of polar Co9S8 and MWCNTs in the three-dimensionally interconnected composites,which contributes to their promising performance for the lithium-sulfur batteries.

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Advances in high carbon dioxide separation performance of poly (ethylene oxide)-based membranes Samaneh Bandehali, Abdolreza Moghadassi, Fahime Parvizian, Sayed Mohsen Hosseini, Takeshi Matsuura, Ezatollah Joudaki 2020, 46(7): 30-52.  DOI: 10.1016/j.jechem.2019.10.019 摘要 ( 16 )   Poly (ethylene-oxide) (PEO)-based membranes have attracted much attention recently for CO2 separation because CO2 is highly soluble into PEO and shows high selectivity over other gases such as CH4 and N2.Unfortunately,those membranes are not strong enough mechanically and highly crystalline,which hinders their broader applications for separation membranes.In this review discussions are made,as much in detail as possible,on the strategies to improve gas separation performance of PEO-based membranes.Some of techniques such as synthesis of graft copolymers that contain PEO,cross-linking of polymers and blending with long chains polymers contributed significantly to improvement of membrane.Incorporation of ionic liquids/nanoparticles has also been found effective.However,surface modification of nanoparticles has been done chemically or physically to enhance their compatibility with polymer matrix.As a result of all such efforts,an excellent performance,i.e.,CO2 permeability up to 200 Barrer,CO2/N2 selectivity up to 200 and CO2/CH4 selectivity up to 70,could be achieved.Another method is to introduce functional groups into PEO-based polymers which boosted CO2 permeability up to 200 Barrer with CO2/CH4 selectivity between 40 and 50.The CO2 permeability of PEO-based membranes increases,without much change in selectivity,when the length of ethylene oxide is increased.

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Potassium pre-inserted K1.04Mn8O16 as cathode materials for aqueous Li-ion and Na-ion hybrid capacitors Yamin Zhang, Lina Chen, Chongyang Hao, Xiaowen Zheng, Yixuan Guo, Long Chen, Kangrong Lai, Yinghe Zhang, Lijie Ci 2020, 46(7): 53-61.  DOI: 10.1016/j.jechem.2019.10.015 摘要 ( 5 )   For the applications of aqueous Li-ion hybrid capacitors and Na-ion hybrid capacitors,potassium ions are pre-inserted into MnO2 tunnel structure,the as-prepared K1.04Mn8O16 materials consist of nanoparticles and nanorods were prepared by facile high-temperature solid-state reaction.The as-prepared materials were well studied and they show outstanding electrochemical behavior.We assembled hybrid supercapacitors with commercial activated carbon (YEC-8A) as anode and K1.04Mn8O16 as cathode.It shows high energy and power densities.Li-ion capacitors reach a high energy density of 127.61 Wh kg-1 at the power density of 99.86 W kg-1 and Na-ion capacitor obtains 170.96 Wh kg-1 at 133.79 W kg-1.In addition,the hybrid supercapacitors demonstrate excellent cycling performance which maintain 97% capacitance retention for Li-ion capacitor and 85% for Na-ion capacitor after 10,000 cycles.

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Electrochemical ageing study of mixed lanthanum/ praseodymium nickelates La2-xPrxNiO4+δ as oxygen electrodes for solid oxide fuel or electrolysis cells Vaibhav Vibhu, Aurélien Flura, Aline Rougier, Clément Nicollet, Sébastien Fourcade, Teresa Hungria, Jean-Claude Grenier, Jean-Marc Bassat 2020, 46(7): 62-70.  DOI: 10.1016/j.jechem.2019.10.012 摘要 ( 12 )   The chemical and electrochemical stability of lanthanide nickelates La2NiO4+δ (LNO),Pr2NiO4+δ (PNO) and their mixed compounds La2-xPrxNiO4+δ (LPNOs) with x=0.5,1 or 1.5 is reported.The aim is to promote these materials as efficient electrodes for solid oxide fuel cell (SOFC) and/or solid oxide electrolysis cell (SOEC).La2NiO4+δ and La1.5Pr0.5NiO4+δ compounds are chemically very stable as powders over one month in the temperature range 600-800 ℃,while the other materials rich in praseodymium progressively decompose into various perovskite-deriving components with additional Pr6O11.Despite their uneven properties,all these materials are quite efficient and sustainable as electrodes on top of gadolinium doped ceria (GDCBL) // yttrium doped zirconia (8YSZ) electrolyte,for one month at 700 ℃ without polarization.Under polarization (300 mA·cm-2),the electrochemical performances of LNO,PNO and La1.5Pr0.5NiO4+δ (LP5NO) quickly degrade in SOFC mode,i.e.for the oxygen reduction reaction,while they show durability in SOEC mode,i.e.for the oxide oxidation reaction.

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Simple synthesis of sandwich-like SnSe2/rGO as high initial coulombic efficiency and high stability anode for sodium-ion batteries Tingting Wang, Kaiwei Yang, Juan Shi, Shangrui Zhou, Liwei Mi, Hongping Li, Weihua Chen 2020, 46(7): 71-77.  DOI: 10.1016/j.jechem.2019.10.021 摘要 ( 8 )   Metal selenides owing to their high theoretical capacity and good conductivity are considered as one of the potential candidates for the anode materials of sodium-ion batteries (SIBs).However,their practical applications are greatly restricted by the poor cycling performances and complicated synthesis methods.In this work,a sandwich-like SnSe2/reduced graphene oxide (rGO) composite with a small amount of rGO (7.3%) is synthesized by a simple one-pot solvothermal technique.The as-synthesized SnSe2/rGO shows improved initial coulombic efficiency (ICE) of 73.7%,high capacity of 402.0 mAh g-1 after 150 cycles at 0.1 A g-1 with a retention of 86.2% and outstanding rate performances.The abundant Sn-O-C bonds of synthesized material not only accelerate the charge transfer at the interface but also enhance the mechanical strength to accommodate volume variation and prevent active material loss during cycling.Moreover,the compact structure leads to thin solid electrolyte interface (SEI) so that high initial coulombic efficiency was obtained.Furthermore,full cells are assembled to test its potential application.This work offers a simple method to synthesize SnSe2/rGO as a candidate anode for SIBs.

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N-heterocyclic carbene as a promising metal-free electrocatalyst with high efficiency for nitrogen reduction to ammonia Hongyan Li, Le Yang, Zhongxu Wang, Peng Jin, Jingxiang Zhao, Zhongfang Chen 2020, 46(7): 78-86.  DOI: 10.1016/j.jechem.2019.10.016 摘要 ( 10 )   Electrocatalytic nitrogen reduction reaction (NRR) at ambient conditions holds great promise for sustainably synthesizing ammonia (NH3),while developing highly-efficient,long-term stable,and inexpensive catalysts to activate the inert N≡N bond is a key scientific issue.In this work,on the basis of the concept “N-heterocyclic carbenes (NHCs)”,we propose a carbon decorated graphitic-carbon nitride (C/g-C3N4) as novel metal-free NRR electrocatalyst by means of density functional theory (DFT) computations.Our results reveal that the introduced C atom in g-C3N4 surface can be regarded as NHCs and catalytic sites for activating N≡N bond,and are stabilized by the g-C3N4 substrate due to sterically disfavored dimerization.Especially,this NHCs-based heterogeneous catalysis can efficiently reduce the activated N2 molecule to NH3 with a low overpotential of 0.05 V via an enzymatic mechanism.Our work is the first report of NHCs-based electrocatalyst for N2 fixation,thus opening an alternative avenue for advancing sustainable NH3 production.

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Quasi-solid-state polymer plastic crystal electrolyte for subzero lithium-ion batteries Yumei Zhou, Fengrui Zhang, Peixin He, Yuhong Zhang, Yiyang Sun, Jingjing Xu, Jianchen Hu, Haiyang Zhang, Xiaodong Wu 2020, 46(7): 87-93.  DOI: 10.1016/j.jechem.2019.11.001 摘要 ( 25 )   Succinonitrile (SN)-based polymer plastic crystal electrolytes (PPCEs) have attracted considerable attention as solid-state electrolytes owing to their high ionic conductivities similar to those of liquid electrolytes,excellent contacts with the electrodes,and good mechanic properties.As a crucial property of a solid-state electrolyte,the ionic conductivity of the PPCE directly depends on the interactions between the constituent parts including the polymer,lithium salt,and SN.A few studies have focused on the effects of polymer-lithium-salt and polymer-SN interactions on the PPCE ionic conductivity.Nevertheless,the impact of the lithium-salt-SN combination on the PPCE ionic conductivity has not been analyzed.In particular,tuning of the lithium-salt-SN interaction to fabricate a subzero PPCE with a high low-temperature ionic conductivity has not been reported.In this study,we design and fabricate five PPCE membranes with different weight ratios of LiN(SO2CF3)2 (LiTFSI) and SN to investigate the effect of the LiTFSI-SN interaction on the PPCE ionic conductivity.The ionic conductivities of the five PPCEs are investigated in the temperature range of -20 to 60 ℃ by electro-chemical impedance spectroscopy.The interaction is analyzed by Fourier-transform infrared spectroscopy,Raman spectroscopy,and differential scanning calorimetry.The LiTFSI-SN interaction significantly influences the melting point of the PPCE,dissociation of the LiTFSI salt,and thus the PPCE ionic conductivity.By tuning the LiTFSI-SN interaction,a subzero workable PPCE membrane having an excellent low-temperature ionic conductivity (6×10-4 S cm-1 at 0 ℃) is obtained.The electro-chemical performance of the optimal PPCE is evaluated by using a LiCoO2/PPCE/Li4Ti5O12 cell,which confirms the application feasibility of the proposed quasisolid-state electrolyte in subzero workable lithium-ion batteries.

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Hierarchical N-doped carbon nanocages/carbon textiles as a flexible O2 electrode for Li-O2 batteries Jia Liu, Dan Li, Siqi Zhang, Ying Wang, Guiru Sun, Zhao Wang, Haiming Xie, Liqun Sun 2020, 46(7): 94-98.  DOI: 10.1016/j.jechem.2019.10.024 摘要 ( 11 )   The conventional Li-O2 battery (LOB) has hardly been considered as a next-generation flexible electronics thus far,since it is bulk,inflexible and limited by the absence of an adjustable cell configuration.Here,we present a flexible Li-O2 cell using N-doped carbon nanocages grown onto the carbon textiles (NCNs/CTs) as a self-standing and binder-free O2 electrode.The highly flexible NCNs/CTs exhibits an excellent mechanic durability,a promising catalytic activity towards the ORR and OER,a considerable cyclability of more than 70 cycles with an overpotential of 0.36 V on the 1st cycle at a constant current density of 0.2 mA/cm2,a good rate capability,a superior reversibility with formation and decomposition of desired Li2O2,and a highly electrochemical stability even under stringent bending and twisting conditions.Our work represents a promising progress in the material development and architecture design of O2 electrode for flexible LOBs.

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A multi-functional binder for high loading sulfur cathode Ying Chu, Ning Chen, Ximing Cui, Anmin Liu, Liang Zhen, Qinmin Pan 2020, 46(7): 99-104.  DOI: 10.1016/j.jechem.2019.10.020 摘要 ( 12 )   Lithium sulfur (Li-S) batteries are the promising power sources,but their commercialization is significantly impeded by poor energy-storage functions at high sulfur loading.Here we report that such an issue can be effectively addressed by using a mussel-inspired binder comprised of chitosan grafted with catecholic moiety for sulfur cathodes.The resulting sulfur cathodes possess a high loading up to 12.2 mg cm-2 but also exhibit one of the best electrochemical properties among their counterparts.The excellent performances are attributed to the strong adhesion of the binder to sulfur particles,conducting agent,current collector,and polysulfide.The versatile adhesion effectively increases the sulfur loading,depresses the shuttle effect,and alleviates mechanical pulverization during cycling processes.The present investigation offers a new insight into high performance sulfur cathodes through a bio-adhesion viewpoint.

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Electrostatic self-assembly of MXene and edge-rich CoAl layered double hydroxide on molecular-scale with superhigh volumetric performances Hao Niu, Xue Yang, Qian Wang, Xiaoyan Jing, Kui Cheng, Kai Zhu, Ke Ye, Guiling Wang, Dianxue Cao, Jun Yan 2020, 46(7): 105-113.  DOI: 10.1016/j.jechem.2019.10.023 摘要 ( 31 )   It is highly desirable to design and synthesize two-dimensional nanostructured electrode materials with high electrical conductivity,large electrolyte-accessible surface area and more exposed active sites for energy storage applications.Herein,MXene/CoAl-LDH heterostructure has been prepared through electrostatic ordered hetero-assembly of monolayer MXene and edge-rich CoAl-LDH nanosheets in a faceto-face manner on molecular-scale for supercapacitor applications.Benefiting from the unique structure,strong interfacial interaction and synergistic effects between MXene and CoAl-LDH nanosheets,the electrical conductivity and exposed electrolyte-accessible active sites are significantly enhanced.The asprepared MXene/CoAl-LDH-80% (ML-80) film exhibits high volumetric capacity of 2472 C cm-3 in 3 M KOH electrolyte with high rate capability of 70.6% at 20 A g-1.Notably,to the best of our knowledge,the high volumetric capacity is the highest among other previously reported values for supercapacitors in aqueous electrolytes.Furthermore,our asymmetric supercapacitor device fabricated with ML-80 and MXene/graphene composite as cathode and anode,respectively,exhibits impressive volumetric energy density of 85.4 Wh L-1 with impressive cycling stability of 94.4% retention ratio after 30,000 continuous charge/discharge cycles.

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P(VDF-HFP)-poly(sulfur-1,3-diisopropenylbenzene) functional polymer electrolyte for lithium-sulfur batteries Jiang-Hui Jiang, An-Bang Wang, Wei-Kun Wang, Zhao-Qing Jin, Li-Zhen Fan 2020, 46(7): 114-122.  DOI: 10.1016/j.jechem.2019.10.009 摘要 ( 12 )   Lithium-sulfur (Li-S) battery as a high-energy density electrochemical energy storage system has attracted many researchers’ attention.However,the shuttle effect of Li-S batteries and the challenges associated with lithium metal anode caused poor cycle performance.In this work,the organosulfide poly(sulfur-1,3-diisopropenylbenzene) (PSD) was prepared as cathode material and additive of P(VDFHFP) polymer electrolyte (P(VDF-HFP)).It was verified that P(VDF-HFP) polymer electrolyte with 10% PSD (P(VDF-HFP)-10%PSD) showed a higher ionic conductivities than that of liquid electrolyte up to 2.27×10-3 S cm-1 at room temperature.The quasi-solid-state Li-S batteries fabricated with organosulfide cathode material PSD and P(VDF-HFP) based functional polymer electrolyte delivered good cycling stability (780 mAh g-1 after 200th cycle at 0.1 C) and rate performance (613 mAh g-1 at 1 C).The good cycling performance could be attributed to the synergistic effect of components,including the interaction between polysulfides and polymer main chain in the organosulfide cathode,the sustained organic/inorganic hybrid stable SEI layer formed by polymer electrolyte additive PSD,the improved cathode/electrolyte interface and the good affinity between P(VDF-HFP) based functional polymer electrolyte and Li metal surface.This strategy herein may provide a new route to fabricate high-performance Li-S batteries through the organosulfide cathode and functional polymer electrolyte.

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Efficient CO2 to CO conversion at moderate temperatures enabled by the cobalt and copper co-doped ferrite oxygen carrier Yu Qiu, Li Ma,dewang Zeng, Min Li, Dongxu Cui, Yulin Lv, Shuai Zhang, Rui Xiao 2020, 46(7): 123-132.  DOI: 10.1016/j.jechem.2019.10.025 摘要 ( 6 )   Chemical looping technology holds great potential on efficient CO2 splitting with much higher CO production and CO2 splitting rate than photocatalytic processes.Conventional oxygen carrier requires high temperature (typically 850-1000 ℃) to ensure sufficient redox activity,but the stable and high CO2 conversion is favored at a lower temperature,leading to the degrading on the reaction kinetics as well as the low CO production and CO2 splitting rate.In this paper,we prepared several ternary spinels and demonstrated their performance for chemical looping CO2 splitting at moderate temperatures.Using the promotion effect of Cu to cobalt ferrite reduction and reversible phase change of the reduced metals,Cu0.4Co0.6Fe2O4 exhibits high CO2 splitting rate (~144.6 μmol g-1 min-1) and total CO production (~9100 μmol g-1) at 650 ℃.The high performance of this earth-abundant spinel material is also consistent in repeated redox cycles,enabling their potential in industrial use.

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Quantitative behavior of vibrational excitation in AC plasma assisted dry reforming of methane Jintao Sun, Qi Chen, Yuanwei Guo, Zili Zhou, Yang Song 2020, 46(7): 133-143.  DOI: 10.1016/j.jechem.2019.11.002 摘要 ( 6 )   Quantitative behavior of non-equilibrium excitation by direct electron impact in low-temperature dry reforming of methane was investigated by integrated studies of experimental validation and kinetic modeling.A plasma chemistry kinetic mechanism incorporating the reactions involving vibrational excitation of CH4,CO2,H2 and CO molecules as well as the low temperature He/CH4/CO2 conversion pathways was developed and validated.The calculation results showed that at lower E/N values (<150 Td) large population of energized electrons generated in a He/CH4/CO2 discharge resulted in an intensification of vibrational excitation.Despite the large generation of vibration,the vibrationally excited molecules in a 0.5/0.25/0.25 of He/CH4/CO2 discharge mixture were easy to relax,due to the strong coupling of the vibration of different molecules in a gas mixture.The results showed that the moderate levels of the vibrational excitation,such as CO2(v10,11,…,18) and CO(v9,10),presented most efficient in the stimulation of species generation including CO,CH2O,CH3OH,C2H4 and C2H6.Specifically,under conditions of E/N of 108 Td,14.9% of CO formation was estimated from the recombination of CO2(v) with CH3 and H,CO2(v)+CH3→CH3O+CO,CO2(v)+H→CO+OH.Also,4.8% of C2H4 formation was from the recombination reaction CH4(v)+CH→C2H4+H.These results highlight the strong roles of vibrational states in a complex plasma chemistry system.

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Identification of reversible insertion-type lithium storage reaction of manganese oxide with long cycle lifespan Yuxuan Zhang, Fang Lian, Jianhao Lu, Laijun Ma, Ning Chen, Yanan Chen, Dingguo Xia 2020, 46(7): 144-151.  DOI: 10.1016/j.jechem.2019.10.022 摘要 ( 3 )   Recently,MnO2 has gained attention as an electrode material because of its very high theoretical capacity and abundant availability.However,the very high volumetric change caused by its conversion-type reaction results in bad reversibility of charge-discharge.In this study,δ-MnO2 of thickness 8 nm anchored on the surface of carbon nanotubes (CNT) by Mn-O-C chemical bonding is synthesized via a facile hydrothermal method.Numerous ex-situ characterizations of the lithium storage process were performed.Furthermore,density functional theory (DFT) calculations indicated that δ-MnO2 (0 1 2) thermodynamically prefers bonding with CNTs.Moreover,the interfacial interaction reinforces the connection of Mn-O and reduces the bond strength of Li-O in lithiated MnO2,which could facilitate an intercalation-type lithium storage reaction.Consequently,the as-synthesized δ-MnO2 retains an excellent reversible capacity of 577.5 mAh g-1 in 1000 cycles at a high rate of 2 A g-1 between 0.1 V and 3.0 V.The results of this study demonstrate the possibility of employing the cost-effective transition metal oxides as intercalation lithium storage dominant electrodes for advanced rechargeable batteries.

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Iridium oxide fabrication and application:A review Hansaem Jang, Jaeyoung Lee 2020, 46(7): 152-172.  DOI: 10.1016/j.jechem.2019.10.026 摘要 ( 19 )   Despite the scarcity and cost of iridium oxide,it is still the material of choice in numerous fields of science and applications,including capacitors,electrochromism,sensors,and various oxidation electrocatalysis (e.g.,chlorine evolution reaction,detoxification,and oxygen evolution reaction).Such versatility is attributed to the distinct features of iridium oxides,such as their activity,biocompatibility,conductivity,and durability.The features and properties of iridium oxides are strongly dependent on the fabrication method.In this review,methodologies relating to the synthesis and fabrication of solid-state iridium oxides have been thoroughly collected and discussed.Structuring and crystallization techniques for iridium oxides are also noted.At the end of the review,the effects of utilizing a certain fabrication method on the characteristics of the iridium oxide product are recapitulated,together with the recommended application of the product in various fields.

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Defect passivation through electrostatic interaction for high performance flexible perovskite solar cells Deyu Xin, Shujie Tie, Xiaojia Zheng, Jianguo Zhu, Wen-Hua Zhang 2020, 46(7): 173-177.  DOI: 10.1016/j.jechem.2019.11.015 摘要 ( 8 )   The light weight,good bending resistance and low production cost make flexible perovskite solar cells (PSCs) good candidates in wearable electronics,portable charger,remote power,and flying objects.High power conversion efficiency (PCE) plays a crucial role on obtaining the high mass specific power of flexible devices.However,the performance for flexible PSCs is still having a large room to be improved.Here,we added the 2-amino-5-cyanopyridine (ACP) molecule with a polar electron density distribution in the perovskite precursor solution to improve the performance of flexible PSCs.The cyano groups with electron-withdrawing ability are expected to passivate positively charged point defects,while amines with electron donating ability are expected to passivate negatively charged point defects in perovskite films.Thanks to the effective passivation of defects at the grain boundary and surface of perovskite films,the PCE of flexible PSCs is obviously increased from 16.9% to 18.0%.These results provide a universal approach to improve performance of flexible PSCs by healing the defects in perovskite films through electrostatic interactions.

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Ni3S2 nanorods growing directly on Ni foam for allsolid-state asymmetric supercapacitor and efficient overall water splitting Baoxin Wu, Hao Qian, Zhongwu Nie, Zhongping Luo, Zixu Wu, Peng Liu, Hao He, Jianghong Wu, Shuguang Chen, Feifei Zhang 2020, 46(7): 178-186.  DOI: 10.1016/j.jechem.2019.11.011 摘要 ( 9 )   Transition metal compounds are attractive for their significant applications in supercapacitors and as non-noble metal catalysts for electrochemical water splitting.Herein,we develop Ni3S2 nanorods growing directly on Ni foam,which act as multifunctional additive-free Ni3S2@Ni electrode for supercapacitor and overall water splitting.Based on PVA-KOH gel electrolyte,the assembled all-solid-state Ni3S2@Ni//AC asymmetric supercapacitor delivers a high areal energy density of 0.52 mWh cm-2 at an areal power density of 9.02 mW cm-2,and exhibits an excellent cycling stability with a capacitance retention ratio of 89% after 10000 GCD cycles at a current density of 30 mA cm-2.For hydrogen evolution reaction and oxygen evolution reaction in 1 M KOH,Ni3S2@Ni electrode achieves a benchmark of 10 mA cm-2 at overpotentials of 82 mV and 310 mV,respectively.Furthermore,the assembled Ni3S2@Ni||Ni3S2@Ni electrolyzer for overall water splitting attains a current density of 10 mA cm-2 at 1.61 V.The in-situ synthesis of Ni3S2@Ni electrode enriches the applications of additive-free transition metal compounds in high-performance energy storage devices and efficient electrocatalysis.

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Engineering a flexible and mechanically strong composite electrolyte for solid-state lithium batteries Tengrui Wang, Ruiqi Zhang, Yongmin Wu, Guannan Zhu, Chenchen Hu, Jiayun Wen, Wei Luo 2020, 46(7): 187-190.  DOI: 10.1016/j.jechem.2019.10.010 摘要 ( 7 )

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Superior de/hydrogenation performances of MgH2 catalyzed by 3D flower-like TiO2@C nanostructures Meng Zhang, Xuezhang Xiao, Bosang Luo, Meijia Liu, Man Chen, Lixin Chen 2020, 46(7): 191-198.  DOI: 10.1016/j.jechem.2019.11.010 摘要 ( 5 )   Magnesium hydride has been seen as a potential material for solid state hydrogen storage,but the kinetics and thermodynamics obstacles have hindered its development and application.Three-dimensional flower-like TiO2@C and TiO2 were synthesized as the catalyst for MgH2 system and great catalytic activities are acquired in the hydrogen sorption properties.Experiments also show that the flower-like TiO2@C is superior to flower-like TiO2 in improving the hydrogen storage properties of MgH2.The hydrogen desorption onset and peak temperatures of flower-like TiO2 doped MgH2 is reduced to 199.2 ℃ and 245.4 ℃,while the primitive MgH2 starts to release hydrogen at 294.6 ℃ and the rapid dehydrogenation temperature is even as high as 362.6 ℃.The onset and peak temperatures of flower-like TiO2@C doped MgH2 are further reduced to 180.3 ℃ and 233.0 ℃.The flower-like TiO2@C doped MgH2 composite can release 6.0 wt% hydrogen at 250 ℃ within 7 min,and 4.86 wt% hydrogen at 225 ℃ within 60 min,while flowerlike TiO2 doped MgH2 can release 6.0 wt% hydrogen at 250 ℃ within 8 min,and 3.89 wt% hydrogen at 225 ℃ within 60 min.Hydrogen absorption kinetics is also improved dramatically.Moreover,compared with primitive MgH2 and the flower-like TiO2 doped MgH2,the activation energy of flower-like TiO2@C doped MgH2 is significantly decreased to 67.10 kJ/mol.All the improvement of hydrogen sorption properties can be ascribed to the flower-like structure and the two-phase coexistence of TiO2 and amorphous carbon.Such phase composition and unique structure are proved to be the critical factor to improve the hydrogen sorption properties of MgH2,which can be considered as the new prospect for improving the kinetics of light-metal hydrogen storage materials.

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Ether-compatible lithium sulfur batteries with robust performance via selenium doping Jin-Lei Qin, Meng Zhao, Hong Yuan, Jia-Qi Huang 2020, 46(7): 199-201.  DOI: 10.1016/j.jechem.2019.11.009 摘要 ( 11 )

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Improving the performance of perovskite solar cells by surface passivation Wenbin Han, Guanhua Ren, Zhiqi Li, Minnan Dong, Chunyu Liu, Wenbin Guo 2020, 46(7): 202-207.  DOI: 10.1016/j.jechem.2019.11.004 摘要 ( 1 )   NiO has a perfect-aligned energy level with CH3NH3PbI3 perovskite such that it serves as a hole transport layer (HTL),but NiO-based perovskite solar cells (PSCs) still suffer from low efficiency due to the poor interface contact between the perovskite layer and the NiO HTL,and haphazardly stacked perovskite grains.Herein,poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT) is introduced between the NiO and perovskite layers in the form of a polymer aggregate to enhance perovskite crystallinity and decrease the interface charge recombination between perovskite and NiO in PSCs,resulting in an improved performance.Moreover,PFBT modified perovskite films showed sharper,smoother,and more compact crystalline grains with fewer grain boundaries,leading to the decreased nonradiative recombination.This study offers a simple strategy to achieve highly efficient PSCs with the incorporation of polymer semiconductor aggregates to passivate the interface between the perovskite and NiO layers.

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Performance improvement of lithium-ion battery by pulse current Shaoqing Zhu, Chen Hu, Ye Xu, Yi Jin, Jianglan Shui 2020, 46(7): 208-214.  DOI: 10.1016/j.jechem.2019.11.007 摘要 ( 34 )   Periodically changed current is called pulse current.It has been found that using the pulse current to charge/discharge lithium-ion batteries can improve the safety and cycle stability of the battery.In this short review,the mechanisms of pulse current improving the performance of lithium-ion batteries are summarized from four aspects:activation,warming up,fast charging and inhibition of lithium dendrites.Related content may help us use the pulse current to improve the performance of lithium-ion batteries and further optimize pulse current technology.

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Additives in metal halide perovskite films and their applications in solar cells Zonghao Liu, Luis K, Ono, Yabing Qi 2020, 46(7): 215-228.  DOI: 10.1016/j.jechem.2019.11.008 摘要 ( 6 )   The booming growth of organic-inorganic hybrid lead halide perovskite solar cells have made this promising photovoltaic technology to leap towards commercialization.One of the most important issues for the evolution from research to practical application of this technology is to achieve high-throughput manufacturing of large-scale perovskite solar modules.In particular,realization of scalable fabrication of large-area perovskite films is one of the essential steps.During the past ten years,a great number of approaches have been developed to deposit high quality perovskite films,to which additives are introduced during the fabrication process of perovskite layers in terms of the perovskite grain growth control,defect reduction,stability enhancement,etc.Herein,we first review the recent progress on additives during the fabrication of large area perovskite films for large scale perovskite solar cells and modules.We then focus on a comprehensive and in-depth understanding of the roles of additives for perovskite grain growth control,defects reduction,and stability enhancement.Further advancement of the scalable fabrication of high-quality perovskite films and solar cells using additives to further develop large area,stable perovskite solar cells are discussed.

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Tuning the base properties of Mg-Al hydrotalcite catalysts using their memory effect Dahye Kwon, Ji Yeon Kang, Suna An, Inchan Yang, Ji Chul Jung 2020, 46(7): 229-236.  DOI: 10.1016/j.jechem.2019.11.013 摘要 ( 19 )   Herein,the relationship between the structure and base properties of Mg-Al hydrotalcite catalysts was comprehensively investigated in relation to heat treatment and rehydration processes,which are well known as memory effects of hydrotalcite.The structure of Mg-Al hydrotalcites changed from layered double hydroxide (LDH) to mixed metal oxide and subsequently to a spinel structure during heat treatment,and it was returned from mixed metal oxide to a LDH structure by rehydration.Based on various characterizations,we successfully proposed a detailed mechanism of memory effect.We also confirmed that the Mg-Al hydrotalcites had weak or strong base sites and that their base properties could be systematically tuned by heat treatment and rehydration.The prepared Mg-Al hydrotalcites were applied to a model reaction,isomerization of glucose to fructose,as base catalysts.Among the catalysts tested,the rehydrated Mg-Al hydrotalcite efficiently produced fructose due to its appropriate base and structure properties.We finally concluded that the base sites of Mg-Al hydrotalcites can be designed as desired by heat treatment and rehydration.Moreover,through systematic design of the base sites of Mg-Al hydrotalcites,these can be promising catalysts for various heterogeneous reactions over base catalysts,giving excellent catalytic performances.

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Lithiated Nafion-garnet ceramic composite electrolyte membrane for solid-state lithium metal battery Jing Gao, Qinjun Shao, Jian Chen 2020, 46(7): 237-247.  DOI: 10.1016/j.jechem.2019.11.012 摘要 ( 13 )   Single-ion conducting solid polymer electrolytes are expected to play a vital role in the realization of solid-state Li metal batteries.In this work,a lithiated Nafion (Li-Nafion)-garnet ceramic Li6.25La3Zr2Al0.25O12 (LLZAO) composite solid electrolyte (CSE) membrane with 30 μm thickness was prepared for the first time.By employing X-ray photoelectron spectroscopy and transmission electron microscope,the interaction between LLZAO and Li-Nafion was investigated.It is found that the LLZAO interacts with the Li-Nafion to form a space charge layer at the interface between LLZAO and Li-Nafion.The space charge layer reduces the migration barrier of Li-ions and improves the ionic conductivity of the CSE membrane.The CSE membrane containing 10 wt% LLZAO exhibits the highest ionic conductivity of 2.26×10-4 S cm-1 at 30 ℃ among the pristine Li-Nafion membrane,the membrane containing 5 wt%,20 wt%,and 30 wt% LLZAO,respectively.It also exhibits a high Li-ion transference number of 0.92,and a broader electrochemical window of 0-+4.8 V vs.Li+/Li than that of 0-+4.0 V vs.Li+/Li for the pristine Li-Nafion membrane.It is observed that the CSE membrane not only inhibits the growth of Li dendrites but also keeps excellent electrochemical stability with the Li electrode.Benefitting from the above merits,the solid-state LiFePO4/Li cell fabricated with the CSE membrane was practically charged and discharged at 30 ℃.The cell exhibits an initial reversible discharge specific capacity of 160 mAh g-1 with 97% capacity retention after 100 cycles at 0.2 C,and maintains discharge specific capacity of 126 mAh g-1 after 500 cycles at 1 C.The CSE membrane prepared with Li-Nafion and LLZAO is proved to be a promising solid electrolyte for advanced solid-state Li metal batteries.

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Hybrid architecture design enhances the areal capacity and cycling life of low-overpotential nanoarray oxygen electrode for lithium-oxygen batteries Liang Xiao, Duo Wang, Ming Li, Bohua Deng, Jinping Liu 2020, 46(7): 248-255.  DOI: 10.1016/j.jechem.2019.11.014 摘要 ( 2 )   Transition metal oxide (TMO) nanoarrays are promising architecture designs for self-supporting oxygen electrodes to achieve high catalytic activities in lithium-oxygen (Li-O2) batteries.However,the poor conductive nature of TMOs and the confined growth of nanostructures on the limited surfaces of electrode substrates result in the low areal capacities of TMO nanoarray electrodes,which seriously deteriorates the intrinsically high energy densities of Li-O2 batteries.Herein,we propose a hybrid nanoarray architecture design that integrates the high electronic conductivity of carbon nanoflakes (CNFs) and the high catalytic activity of Co3O4 nanosheets on carbon cloth (CC).Due to the synergistic effect of two differently featured components,the hybrid nanoarrays (Co3O4-CNF@CC) achieve a high reversible capacity of 3.14 mA h cm-2 that cannot be achieved by only single components.Further,CNFs grown on CC induce the three-dimensionally distributed growth of ultrafine Co3O4 nanosheets to enable the efficient utilization of catalysts.Thus,with the high catalytic efficiency,hybrid Co3O4-CNF@CC also achieves a more prolonged cycling life than pristine TMO nanoarrays.The present work provides a new strategy for improving the performance of nanoarray oxygen electrodes via the hybrid architecture design that integrates the intrinsic properties of each component and induces the three-dimensional distribution of catalysts.

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Rolling up MXene sheets into scrolls to promote their anode performance in lithium-ion batteries Jianing Meng, Fangfang Zhang, Li Zhang, Lingyang Liu, Jiangtao Chen, Bingjun Yang, Xingbin Yan 2020, 46(7): 256-263.  DOI: 10.1016/j.jechem.2019.10.008 摘要 ( 10 )   Although Ti3C2 MXene sheets have attracted extensive attention in lithium-ion storage techniques,their restacking makes against and even hinders the Li ions diffusion within them,thereby decreasing the capacity as well as rate performance of conventional MXene anode.Here,for the first time,we roll up the Ti3C2Tx sheets into scrolls with unclosed topological structure and the interlayer galleries to alleviate the restacking problem.Thus,Ti3C2Tx scrolls as anode materials in lithium-ion batteries (LIBs) have higher capacity and better rate performance than Ti3C2Tx sheets.On the bases of these,high-capacity silicon nanoparticles are added during the rolling process to in-situ produce Ti3C2Tx/Si composite scrolls.The addition of 10% silicon nanoparticles shows the best overall improvement among capacity,rate capability and cyclic stability for Ti3C2Tx scrolls.