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2020, Vol. 40, No. 1　Online: 2020-01-15

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Design of pyrite/carbon nanospheres as high-capacity cathode for lithium-ion batteries Qinqin Xiong, Xiaojing Teng, Jingjing Lou, Guoxiang Pan, Xinhui Xia, Hongzhong Chi, Xiaoxiao Lu, Tao Yang, Zhenguo Ji 2020, 40(1): 1-6.  DOI: 10.1016/j.jechem.2019.02.005 摘要 ( 12 )   Transition metal sulfides are emerging as promising electrode materials for energy storage and conversion. In this work, hierarchical FeS2/C nanospheres are synthesized through a controllable solvothermal method followed by the annealing process. Spherical FeS2 core is homogeneously coated by thin carbon shell. The hierarchical nanostructure and carbon coating can enhance electron transfer and accommodate the stress originated from the volume change as well as suppress the shuttle effect of polysulfide. Consequently, as the cathode material of lithium ion batteries (LIBs), the FeS2/C nanospheres exhibit high reversible capacity of 676 mAh g-1 and excellent cycling life with the capacity retention of 97.1% after 100 cycles. In addition, even at the high current density of 1.8 C, a reversible capacity of 437 mAh g-1 is obtained for the FeS2/C nanospheres, demonstrating its great prospect for practical applications in highperformance LIBs.

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Fabrication of C@MoxTi1-xO2-δ nanocrystalline with functionalized interface as efficient and robust PtRu catalyst support for methanol electrooxidation Jialong Li, Lei Zhao, Xifei Li, Sue Hao, Zhenbo Wang 2020, 40(1): 7-14.  DOI: 10.1016/j.jechem.2019.02.004 摘要 ( 7 )   A core shell structured C@MoxTi1-xO2-δ nanocrystal with a functionalized interface (C@MTNC-FI) was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate. The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process, infiltration of Mo dopants and carbon coating, which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell. PtRu nanoparticles (NPs) were supported on C@MTNC-FI by employing a microwave-assisted polyol process (MAPP). The obtained PtRu/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst (PtRu/C@TNC) and 1.65 times higher mass activity than that of PtRu/C catalyst with over 25% increase in durability. The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries, Mofunctionalized interface with enhanced electron interactions, and core shell architecture with excellent electrical transport properties. This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.

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3D porous V2O5 architectures for high-rate lithium storage Qifei Li, Dong Chen, Huiteng Tan, Xianghua Zhang, Xianhong Rui, Yan Yu 2020, 40(1): 15-21.  DOI: 10.1016/j.jechem.2019.02.010 摘要 ( 5 )   The discovery of novel electrode materials promises to unleash a number of technological advances in lithium-ion batteries. V2O5 is recognized as a high-performance cathode that capitalizes on the rich redox chemistry of vanadium to store lithium. To unlock the full potential of V2O5, nanotechnology solution and rational electrode design are used to imbue V2O5 with high energy and power density by addressing some of their intrinsic disadvantages in macroscopic crystal form. Here, we demonstrate a facile and environmental-friendly method to prepare nanorods-constructed 3D porous V2O5 architectures (3D-V2O5) in large-scale. The 3D porous architecture is found to be responsible for the enhanced charge transfer kinetics and Li-ion diffusion rate of the 3D-V2O5 electrode. As the result, the 3D-V2O5 surpasses the conventional bulk V2O5 by showing enhanced discharge capacity and rate capability (delivering 154 and 127 mAh g-1 at 15 and 20 C, respectively).

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CO2 hydrogenation to methanol over Cu/CeO2 and Cu/ZrO2 catalysts: Tuning methanol selectivity via metal-support interaction Weiwei Wang, Zhenping Qu, Lixin Song, Qiang Fu 2020, 40(1): 22-30.  DOI: 10.1016/j.jechem.2019.03.001 摘要 ( 7 )   Copper-based catalysts for CO2 hydrogenation to methanol are supported on ZrO2 and CeO2, respectively. Reaction results at 3.0 MPa and temperatures between 200 and 300℃ reveal that Cu catalysts supported on ZrO2 and CeO2 exhibit better activity and selectivity than pure Cu catalyst due to Cu-support (ZrO2 and CeO2) interaction. Combining the structural characterizations with in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS), Cu/CeO2 shows the higher methanol selectivity due to the formation of main carbonates intermediates, which are closely related with the oxygen vacancies over Cu/CeO2. In contrast, bicarbonate and carboxyl species are observed on Cu/ZrO2, which originates from the hydroxyl groups presented on catalyst surfaces. Difference in CO2 adsorption intermediates results in the distinct methanol selectivity over the two catalysts.

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Effect of cation (Li+, Na+, K+, Rb+, Cs+) in aqueous electrolyte on the electrochemical redox of Prussian blue analogue (PBA) cathodes Satyajit Phadke, Roman Mysyk, Mérièm Anouti 2020, 40(1): 31-38.  DOI: 10.1016/j.jechem.2019.01.025 摘要 ( 23 )   Prussian blue analogue (PBA) material is a promising cathode for applications in Na-ion and K-ion batteries which can support high c-rates for charge and discharge. In this study, the material of composition[K2CuIIFeII(CN)6] was synthesized and its structural and electrochemical redox behavior was investigated with 5 different alkali insertion cations (Li+, Na+, K+, Rb+, Cs+). Galvanostatic measurements indicate that the redox potential strongly depends on the ionic radius of the inserted cation. The redox potential varies by ～400 mV between using Li+ (0.79 Å) or Cs+ (1.73 Å) in the electrolyte. The underlying modification of the Fe2+/Fe3+ redox potential in PBA is proposed to be due to the weakening of the Fe-C bond in the material. This hypothesis is supported by XRD measurements which reveal that the lattice parameter of the de-intercalated host structure follows the same trend of monotonic increase with the cation size. The relatively minor volume changes accompanying the redox (1.2%-2.4%) allow the PBA to accommodate differently sized cations, although the structural hindrances are quite pronounced at high c-rates for the larger ones (Rb+ and Cs+). Cycle aging studies indicate that the minimum capacity fade rate is observed in case of K+ and Rb+ containing electrolyte. The peak intensity corresponding to the[220] crystallographic plane varies depending on the state of charge of PBA, since this plane contains the insertion cations. Owing to the sensitivity of the redox potential to the insertion cation coupled with the observed fast ion-exchange ability, the PBA material may find additional analytical applications such as ion sensing or filtration devices.

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LiNbO3-coated LiNi0.8Co0.1Mn0.1O2 cathode with high discharge capacity and rate performance for all-solid-state lithium battery Xuelei Li, Liubing Jin, Dawei Song, Hongzhou Zhang, Xixi Shi, Zhenyu Wang, Lianqi Zhang, Lingyun Zhu 2020, 40(1): 39-45.  DOI: 10.1016/j.jechem.2019.02.006 摘要 ( 24 )   In order to obtain high power density, energy density and safe energy storage lithium ion batteries (LIB) to meet growing demand for electronic products, oxide cathodes have been widely explored in all-solidstate lithium batteries (ASSLB) using sulfide solid electrolyte. However, the electrochemical performances are still not satisfactory, due to the high interfacial resistance caused by severe interfacial instability between sulfide solid electrolyte and oxide cathode, especially Ni-rich oxide cathodes, in charge-discharge process. Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) material at present is one of the most key cathode candidates to achieve the high energy density up to 300 Wh kg-1 in liquid LIB, but rarely investigated in ASSLB using sulfide electrolyte. To design the stable interface between NCM811 and sulfide electrolyte should be extremely necessary. In this work, in view of our previous work, LiNbO3 coating with about 1 wt% content is adopted to improve the interfacial stability and the electrochemical performances of NCM811 cathode in ASSLB using Li10GeP2S12 solid electrolyte. Consequently, LiNbO3-coated NCM811 cathode displays the higher discharge capacity and rate performance than the reported oxide electrodes in ASSLB using sulfide solid electrolyte to our knowledge.

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Enhancing cathode performance for CO2 electrolysis with Ce0.9M0.1O2-δ (M=Fe, Co, Ni) catalysts in solid oxide electrolysis cell Zhidong Huang, Zhe Zhao, Huiying Qi, Xiuling Wang, Baofeng Tu, Mojie Cheng 2020, 40(1): 46-51.  DOI: 10.1016/j.jechem.2019.02.007 摘要 ( 8 )   Electrochemical conversion with solid oxide electrolysis cells is a promising technology for CO2 utilization and simultaneously store renewable energy. In this work, Ce0.9M0.1O2-δ (CeM, M=Fe, Co, Ni) catalysts are infiltrated into La0.6Sr0.4Cr0.5Fe0.5O3-δ-Gd0.2Ce0.8O2-δ (LSCrFe-GDC) cathode to enhance the electrochemical performance for CO2 electrolysis. CeCo-LSCrFe-GDC cell obtains the best performance with a current density of 0.652 A cm-2, followed by CeFe-LSCrFe-GDC and CeNi-LSCrFe-GDC cells with the value of 0.603 and 0.535 A cm-2, respectively, about 2.44, 2.26 and 2.01 times higher than that of the LSCrFe-GDC cell at 1.5 V and 800℃. Electrochemical impedance spectra combined with distributions of relaxed times analysis shows that both CO2 adsorption process and the dissociation of CO2 at triple phase boundaries are accelerated by CeM catalysts, while the latter is the key rate-determining step.

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Improved hydrogen oxidation reaction under alkaline conditions by Au-Pt alloy nanoparticles Lijuan Lu, Lishan Peng, Li Li, Jing Li, Xun Huang, Zidong Wei 2020, 40(1): 52-56.  DOI: 10.1016/j.jechem.2019.02.008 摘要 ( 8 )   This work demonstrates the outstanding performance of alloyed Au1Pt1 nanoparticles on hydrogen oxidation reaction (HOR) in alkaline solution. Due to the weakened hydrogen binding energy caused by uniform incorporation of Au, the alloyed Au1Pt1/C nanoparticles exhibit superior HOR activity than commercial PtRu/C. On the contrary, the catalytic performance of the phase-segregated Au2Pt1/C and Au1Pt1/C bimetallic nanoparticles in HOR is significantly worse. Moreover, Au1Pt1/C shows a remarkable durability with activity dropping only 4% after 3000 CV cycles, while performance attenuation of commercial PtRu/C is high up to 15% under the same condition. Our results indicate that the alloyed Au1Pt1/C is a promising candidate to substitute commercial PtRu/C for hydrogen oxidation reaction in alkaline electrolyte.

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Tetra-alkylsulfonate functionalized poly(aryl ether) membranes with nanosized hydrophilic channels for efficient proton conduction Lijun Zhou, Junyang Zhu, Meijin Lin, Jiaqi Xu, Zailai Xie, Dongyang Chen 2020, 40(1): 57-64.  DOI: 10.1016/j.jechem.2019.02.013 摘要 ( 5 )   The microstructure of polymer electrolyte membranes plays a key role in ion conductivity and water transport. Herein, fluorinated poly(aryl ether)s with tetra-alkylsulfonate side chains (SFPAEs) have been successfully synthesized from the copolymerization of a newly developed tetra-allyl-containing bisphenol (TABP) monomer, followed by the thiol-ene addition with sodium 3-mercapto-1-propanesulfonate to attach the ionic groups at the end of the flexible chains. Being the first of its kind, the densely distributed and lengthy alkylsulfonate group possesses the benefit of ease to self-assemble into hydrophilic domains during membrane preparation via solution casting. Indeed, the TEM characterizations revealed that distinct hydrophilic channels of ~1-2 nm width had been formed, much larger than those of a home-made control sample where only di-alkylsulfonate side chains were attached. The SFPAE-4-45 with an IECw of 2.0 mmol g-1 exhibited an enhanced proton conductivity of 143.7 mS cm-1 at room temperature, which was superior to that of Nafion 212 (91.0 mS cm-1). Furthermore, the oxidative stabilities of SFPAEs were significantly higher than those of non-fluorinated analogs in literature. This study offered a new route to engineering the pendent structure of ionomers for well-defined microscopic morphologies.

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Towards high-performance tubular-type protonic ceramic electrolysis cells with all-Ni-based functional electrodes Artem Tarutin, Anna Kasyanova, Julia Lyagaeva, Gennady Vdovin, Dmitry Medvedev 2020, 40(1): 65-74.  DOI: 10.1016/j.jechem.2019.02.014 摘要 ( 17 )   Protonic ceramic electrolysis cells (PCECs), which permit high-temperature electrolysis of water, exhibit various advantages over conventional solid oxide electrolysis cells (SOECs), including cost-effectiveness and the potential to operate at low-/intermediate-temperature ranges with high performance and efficiency. Although many efforts have been made in recent years to improve the electrochemical characteristics of PCECs, certain challenges involved in scaling them up remain unresolved. In the present work, we present a twin approach of combining the tape-calendering method with all-Ni-based functional electrodes with the aim of fabricating a tubular-designed PCEC having an enlarged electrode area (4.6 cm2). This cell, based on a 25 μm-thick BaCe0.5Zr0.3Dy0.2O3-δ proton-conducting electrolyte, a nickelbased cermet and a Pr1.95Ba0.05NiO4+δ oxygen electrode, demonstrates a high hydrogen production rate (19 mL min-1 at 600℃), which surpasses the majority of results reported for traditional button- or planar-type PCECs. These findings increase the scope for scaling up solid oxide electrochemical cells and maintaining their operability at reducing temperatures.

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Thiourea-assisted coating of dispersed copper electrocatalysts on Si photocathodes for solar hydrogen production Pin Wang, Ziyu Yin, Linfeng Gao, Hui Li, Tongyu Zhang, Qing Shen, Jun Lv, Yingfang Yao, Wenjun Luo, Zhigang Zou 2020, 40(1): 75-80.  DOI: 10.1016/j.jechem.2019.02.012 摘要 ( 7 )   Photoelectrochemical water splitting can convert solar energy into clean hydrogen energy for storage. It is desirable to explore non-precious electrocatalysts for practical applications of a photoelectrode in a large scale. Here, we developed a facile spin-coating and in-situ photoelectrochemical reduction method to prepare a dispersed Cu electrocatalyst on a Si photocathode, which improves the performance remarkably. We find that thiourea in the precursor solution for spin-coating plays an important role in obtaining dispersed Cu particles on the surface of a Si photoelectrode. With thiourea in the precursor, the Cu/Si photocathode shows higher performance than the one without thiourea. Moreover, the Cu/Si photocathode also indicates good stability after 16 h illumination.

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Platinum nanoparticles coated by graphene layers: A low-metal loading catalyst for methanol oxidation in alkaline media Camelia Berghian-Grosan, Teodora Radu, Alexandru R. Biris, Monica Dan, Cezara Voica, Fumiya Watanabe, Alexandru S. Biris, Adriana Vulcu 2020, 40(1): 81-88.  DOI: 10.1016/j.jechem.2019.03.003 摘要 ( 8 )   Platinum catalysts play a major role in the large scale commercialization of direct methanol fuel cells (DMFC). Here, we present a procedure to create a nanostructural graphene-platinum (GrPt) composite containing a small amount (5.3 wt%) of platinum nanoparticles coated with at least four layers of graphene. The composite, as GrPt ink, was deposited on a glassy carbon electrode and its electrocatalytic activity in a methanol oxidation reaction (MOR) was evaluated in a 1 M CH3OH/1 M NaOH solution. The results indicated an enhanced catalytic performance of GrPt towards MOR in alkaline media compared with the Pt/C material. Electron energy-loss spectroscopy and X-ray photoelectron spectroscopy (recorded before and after the electrochemical assays) were employed to analyze the changes in the chemical composition of the nanomaterial and to explain the transformations that took place at the electrode surface. Our findings suggest that growing of graphene on platinum nanoparticles improve the catalytic performance of platinum-graphene composites towards MOR in alkaline media.

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Facile preparation of core-shell Si@Li4Ti5O12 nanocomposite as large-capacity lithium-ion battery anode Mengjing Liu, Hanyang Gao, Guoxin Hu, Kunxu Zhu, Hao Huang 2020, 40(1): 89-98.  DOI: 10.1016/j.jechem.2019.02.011 摘要 ( 7 )   As a promising alternative anode material, silicon (Si) presents a larger capacity than the commercial anode to achieve large capacity lithium-ion batteries. However, the application of pure Si as anode is hampered by limitations such as volume expansion, low conductivity and unstable solid electrolyte interphase. To break through these limitations, the core-shell Si@Li4Ti5O12 nanocomposite, which was prepared via in-situ self-assembly reaction and decompressive boiling fast concentration method, was proposed in this work. This anode combines the advantages of nano-sized Si particle and pure Li4Ti5O12 (LTO) coating layer, improving the performance of the lithium-ion batteries. The Si@Li4Ti5O12 anode displays a high initial discharge/charge specific capacity of 1756/1383 mAh g-1 at 500 mA g-1 (representing high initial coulombic efficiency of 78.8%), a large rate capability (specific capacity of 620 mAh g-1 at 4000 mA g-1), an outstanding cycling stability (reversible specific capacity of 883 mAh g-1 after 150 cycles) and a low volume expansion rate (only 3.3% after 150 cycles). Moreover, the synthesis process shows the merits of efficiency, simplicity, and economy, providing a reliable method to fabricate large capacity Si@Li4Ti5O12 nanocomposite anode materials for practical lithium-ion batteries.

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Hexagonal boron nitride adsorbent: Synthesis, performance tailoring and applications Jun Xiong, Jun Di, Wenshuai Zhu, Huaming Li 2020, 40(1): 99-111.  DOI: 10.1016/j.jechem.2019.03.002 摘要 ( 14 )   Hexagonal boron nitride (h-BN), with unique structural and properties, has shown enormous potential toward variety of possible applications. By virtue of partially-ionic character of BN chemical bonds and usually large specific surface area, h-BN-related nanostructures exhibit appealing adsorption properties, which can be widely applied for separation and purification towards energy and environment treatment. In this review, recent progress in designing h-BN micro, nano-structure, controlled synthesis, performance optimizing as well as energy and environment-related adsorption applications are summarized. Strategies to tailor the h-BN can be classified as morphology control, element doping, defect control and surface modification, focusing on how to optimize the adsorption performance. In order to insight the intrinsic mechanism of tuning strategies for property optimization, the significant adsorption applications of h-BN towards hydrogen storage, CO2 capture, pollutants removal from water and adsorption desulfurization are presented.

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Tuning the optoelectronic properties of vinylene linked perylenediimide dimer by ring annulation at the inside or outside bay positions for fullerene-free organic solar cells Jing Yang, Fan Chen, Peiqing Cong, Hongjun Xiao, Yanfang Geng, Zhihui Liao, Lie Chen, Bao Zhang, Erjun Zhou 2020, 40(1): 112-119.  DOI: 10.1016/j.jechem.2019.03.007 摘要 ( 12 )   Among various perylenediimide (PDI)-based small molecular non-fullerene acceptors (NFAs), PDI dimer can effectively avoid the excessive aggregation of single PDI and improve the photovoltaic performance. However, the twist of perylene core in PDI dimer will destroy the effective conjugation. Thus, ring annulation of PDI dimer is a feasible method to balance the film quality and electron transport, but the systematic study has attracted few attentions. Herein, we choose a simple vinylene linked PDI dimer, V-PDI2, and then conduct further studies on the structure-property-performance relationship of four kinds of derived fused-PDI dimers, namely V-TDI2, V-FDI2, V-PDIS2 and V-PDISe2 respectively. The former two are incorporated thianaphthene and benzofuran at the inside bay positions, and the latter two are fused thiophene and selenophene at the outside bay positions, respectively. Theoretical calculations reveal the inside- and outside-fused structures largely affect the skeleton configuration, the former two tend to be planar structure and the latter two maintain the distorted backbone. The photovoltaic characterizations show that the inside-fused PDI dimers offer high open circuit voltage (VOC), while the outside-fused PDI dimers afford large short-circuit current density (JSC). This variation tendency results from the reasonably tunable energy levels, light absorption, molecular crystallinity and film morphology. As a result, PBDB-T:V-PDISe2 device exhibits the highest power conversion efficiency (PCE) of 6.51%, and PBDB-T:VFDI2 device realizes the highest VOC of 1.00 V. This contribution indicates that annulation of PDI dimers in outside or inside bay regions is a feasible method to modulate the properties of PDI-based non-fullerene acceptors.

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Fabrication and study of supercapacitor electrodes based on oxygen plasma functionalized carbon nanotube fibers Paa Kwasi Adusei, Seyram Gbordzoe, Sathya Narayan Kanakaraj, Yu-Yun Hsieh, Noe T. Alvarez, Yanbo Fang, Kevin Johnson, Colin McConnell, Vesselin Shanov 2020, 40(1): 120-131.  DOI: 10.1016/j.jechem.2019.03.005 摘要 ( 25 )   Dry-spun Carbon Nanotube (CNT) fibers were surface-modified by atmospheric pressure oxygen plasma functionalization using a well controlled and continuous process. The fibers were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). It was found from the conducted electrochemical measurements that the functionalized fibers showed a 132.8% increase in specific capacitance compared to non-functionalized fibers. Dye-adsorption test and the obtained Randles-Sevcik plot demonstrated that the oxygen plasma functionalized fibers exhibited increased surface area. It was further established by Brunauer-Emmett-Teller (BET) measurements that the surface area of the CNT fibers was increased from 168.22 m2/g to 208.01 m2/g after plasma functionalization. The pore size distribution of the fibers was also altered by this processing. The improved electrochemical data was attributed to enhanced wettability, increased surface area, and the presence of oxygen functional groups, which promoted the capacitance of the fibers. Fiber supercapacitors were fabricated from the oxygen plasma functionalized CNT fiber electrodes using different electrolyte systems. The devices with functionalized electrodes exhibited excellent cyclic stability (93.2% after 4000 cycles), flexibility, bendability, and good energy densities. At 0.5 mA/cm2, the EMIMBF4 device revealed a specific capacitance, which is 27% and 65% greater than the specific capacitances of devices using EMIMTFSI and H2SO4 electrolytes, respectively. The practiced in this work plasma surface processing can be employed in other applications where fibers, yarns, ribbons, and sheets need to be chemically modified.

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La2Zr2O7 and MgO co-doped composite Li-Garnet solid electrolyte Jiu Lin, Linbin Wu, Zhen Huang, Xiaoxiong Xu, Jiheng Liu 2020, 40(1): 132-136.  DOI: 10.1016/j.jechem.2019.02.003 摘要 ( 23 )

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Metal-organic-framework-derived formation of Co-N-doped carbon materials for efficient oxygen reduction reaction Hao Tian, Chi Zhang, Panpan Su, Zhangfeng Shen, Hao Liu, Guoxiu Wang, Shaomin Liu, Jian Liu 2020, 40(1): 137-143.  DOI: 10.1016/j.jechem.2019.03.004 摘要 ( 19 )   Non-precious metal nitrogen-doped carbonaceous materials have attracted tremendous attention in the field of electrochemical energy storage and conversion. Herein, we report the designed synthesis of a novel series of Co-N-C nanocomposites and their evaluation of electrochemical properties. Novel yolkshell structured Co nanoparticles@polymer materials are fabricated from the facile coating polymer strategy on the surface of ZIF-67. After calcination in nitrogen atmosphere, the Co-N-C nanocomposites in which cobalt metal nanoparticles are embedded in the highly porous and graphitic carbon matrix are successfully achieved. The cobalt nanoparticles containing cobalt metal crystallites with an oxidized shell and/or smaller (or amorphous) cobalt-oxide deposits appear on the surface of graphitic carbons. The prepared Co-N-C nanoparticles showed favorable electrocatalytic activity for oxygen reduction reactions, which is attributed to its high graphitic degree, large surface area and the large amount existence of Co-N active sites.

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Heteroatom substitution-induced asymmetric A-D-A type non-fullerene acceptor for efficient organic solar cells Chao Li, Jiali Song, Yunhao Cai, Guangchao Han, Wenyu Zheng, Yuanping Yi, Hwa Sook Ryu, Han Young Woo, Yanming Sun 2020, 40(1): 144-150.  DOI: 10.1016/j.jechem.2019.03.009 摘要 ( 15 )   Research on asymmetric A-D-A structured non-fullerene acceptors has lagged far behind the development of symmetric counterpart. In this contribution, by simply replacing one sulfur atom in indacenodithiophene unit with a selenium atom, an asymmetric building block SePT and a corresponding asymmetric non-fullerene acceptor SePT-IN have been developed. Asymmetric SePT-IN achieved a high efficiency of 10.20% in organic solar cells when blended with PBT1-C, much higher than that of symmetric TPT-IN counterpart (8.91%). Our results demonstrated an effective heteroatom substitution strategy to develop asymmetric A-D-A structured non-fullerene acceptors.

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CNTs@S composite as cathode for all-solid-state lithium-sulfur batteries with ultralong cycle life Qiang Zhang, Ning Huang, Zhen Huang, Liangting Cai, Jinghua Wu, Xiayin Yao 2020, 40(1): 151-155.  DOI: 10.1016/j.jechem.2019.03.006 摘要 ( 24 )   The main challenges in development of traditional liquid lithium-sulfur batteries are the shuttle effect at the cathode caused by the polysulfide and the safety concern at the Li metal anode arose from the dendrite formation. All-solid-state lithium-sulfur batteries have been proposed to solve the shuttle effect and prevent short circuits. However, solid-solid contacts between the electrodes and the electrolyte increase the interface resistance and stress/strain, which could result in the limited electrochemical performances. In this work, the cathode of all-solid-state lithium-sulfur batteries is prepared by depositing sulfur on the surface of the carbon nanotubes (CNTs@S) and further mixing with Li10GeP2S12 electrolyte and acetylene black agents. At 60℃, CNTs@S electrode exhibits superior electrochemical performance, delivering the reversible discharge capacities of 1193.3, 959.5, 813.1, 569.6 and 395.5 mAh g-1 at the rate of 0.1, 0.5, 1, 2 and 5 C, respectively. Moreover, the CNTs@S is able to demonstrate superior high-rate capability of 660.3 mAh g-1 and cycling stability of 400 cycles at a high rate of 1.0 C. Such uniform distribution of the CNTs, S and Li10GeP2S12 electrolyte increase the electronic and ionic conductivity between the cathode and the electrolyte hence improves the rate performance and capacity retention.

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Metal-organic frameworks for electrochemical reduction of carbon dioxide: The role of metal centers Ping Shao, Luocai Yi, Shumei Chen, Tianhua Zhou, Jian Zhang 2020, 40(1): 156-170.  DOI: 10.1016/j.jechem.2019.04.013 摘要 ( 64 )   Direct electrochemical reduction of CO2 into valuable chemicals and fuel is one of the most promising approaches to address the current energy crisis and lower CO2 emission. Recently, numerous metal-organic framework (MOF) and their derived materials have extensively been developed as electrocatalysts for CO2 reduction owing to their unique structure including porosity, large specific surface area, and tunable chemical structures. In this review, the recent progress of MOF-based electrocatalysts for CO2 reduction was summarized and discussed. Detailed discussions mainly focus on the synthesis and mechanism of pristine MOFs and MOF-derived materials for electrocatalytic CO2 reduction. These examples are expected to provide clues to rational design and synthesis of stable and high-performance MOFs-based electrocatalysts for CO2 reduction.

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Preparation of high-purity straight silicon nanowires by molten salt electrolysis Jie Zhang, Sheng Fang, Xiaopeng Qi, Zhanglong Yu, Zhaohui Wu, Juanyu Yang, Shigang Lu 2020, 40(1): 171-179.  DOI: 10.1016/j.jechem.2019.04.014 摘要 ( 9 )   Silicon nanowires of high purity and regular morphology are of prime importance to ensure high specific capacities of lithium-ion batteries and reproducible electrode assembly process. Using nickel formate as a metal catalyst precursor, straight silicon nanowires (65-150 nm in diameter) were directly prepared by electrolysis from the Ni/SiO2 porous pellets with 0.8 wt% nickel content in molten CaCl2 at 900℃. Benefiting from their straight appearance and high purity, the silicon nanowires therefore offered an initial coulombic efficiency of 90.53% and specific capacity of 3377 mAh/g. In addition, the silicon nanowire/carbon composite exhibited excellent cycle performance, retaining 90.38% of the initial capacity after 100 cycles. Whilst further study on the charge storage performance is still ongoing, these preliminary results demonstrate that nickel formate is an efficient and effective metal catalyst precursor for catalytic preparation of high purity straight silicon nanowires via the molten salt electrolysis, which is suitable for large-scale production.

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Low-bandgap polymers with quinoid unit as π bridge for high-performance solar cells Bilal Shahid, Xiyue Yuan, Qian Wang, Di Zhou, Ergang Wang, Xichang Bao, Dangqiang Zhu, Renqiang Yang 2020, 40(1): 180-187.  DOI: 10.1016/j.jechem.2019.04.007 摘要 ( 16 )   To construct efficient low band gap polymers, increasing the Quinone structure of the polymer backbone could be one desirable strategy. In this work, two D-Q-A-Q polymers P1 and P2 were designed and synthesized with thiophenopyrrole diketone (TPD) and benzothiadiazole (BT) unit as the core and ester linked thieno[3,4-b]thiophene (TT) segment as π-bridging, and the main focus is to make a comparative analysis of different cores in the influence of the optical, electrochemical, photochemical and morphological properties. Compared with the reported PBDTTEH-TBTTHD-i, P1 exhibited the decreased HOMO energy level of -5.38 eV and lower bandgap of 1.48 eV. Furthermore, when replaced with BT core, P2 showed a red-shifted absorption profile of polymer but with up-shifted HOMO energy level. When fabricated the photovoltaic devices in conventional structure, just as expected, the introduction of ester substituent made an obvious increase of VOC from 0.63 to 0.74 V for P1. Besides, due to the deep HOMO energy level, higher hole mobility and excellent phase separation with PC71BM, a superior photovoltaic performance (PCE=7.13%) was obtained with a short-circuit current density (JSC) of 14.9 mA/cm2, significantly higher than that of P2 (PCE=2.23%). Generally, this study highlights that the strategy of inserting quinoid moieties into D-A polymers could be optional in LBG-polymers design and presents the importance and comparison of potentially competent core groups.

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Bimetallic Ru-Ni/TiO2 catalysts for hydrogenation of N-ethylcarbazole: Role of TiO2 crystal structure Hongen Yu, Xue Yang, Yong Wu, Yanru Guo, Shuan Li, Wei Lin, Xingguo Li, Jie Zheng 2020, 40(1): 188-195.  DOI: 10.1016/j.jechem.2019.04.009 摘要 ( 13 )   Hydrogenation of N-ethylcarbazole (NEC), the hydrogen lean form of a liquid organic hydrogen carrier, on TiO2 supported Ru-Ni bimetallic catalysts is investigated. Crystal structure of TiO2 plays a critical role on the hydrogenation activity and selectivity towards fully hydrogenated product. Ru/anatase catalyst exhibits higher selectivity but lower reactivity compared to Ru/rutile catalyst. Ni addition significantly promotes the performance of Ru/anatase catalyst while causes severe performance deterioration of Ru/rutile catalyst. Commercial P25, a mixture of anatase and rutile phases in approximate ratio A/R～1/4, is found to be the best TiO2 support for NEC hydrogenation. Ru/P25 catalyst outperforms both Ru/rutile and Ru/anatase and its activity can be further slightly improved by Ni addition. The unexpected synergism between the two different TiO2 phases for Ru based NEC hydrogenation catalysts is related to metal-support interaction and Ru-Ni interaction.

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Highly efficient solution-processed CZTSSe solar cells based on a convenient sodium-incorporated post-treatment method Biwen Duan, Linbao Guo, Qing Yu, Jiangjian Shi, Huijue Wu, Yanhong Luo, Dongmei Li, Sixin Wu, Zhi Zheng, Qingbo Meng 2020, 40(1): 196-203.  DOI: 10.1016/j.jechem.2019.03.029 摘要 ( 55 )   In CZTSSe solar cells, a simple sodium-incorporation post-treatment method toward solution-processed Cu2ZnSnS4 precursor films is presented in this work. An ultrathin NaCl film is deposited on Cu2ZnSnS4 precursor films by spin-coating NaCl solution. In subsequent selenization process, the introduction of NaCl is found to be benefacial for the formation of Cu2-xSe, which can further facilitate the element transportation, leading to dense and smooth CZTSSe films with large grains and less impurity Cu2Sn(S,Se)3 phase. SIMS depth profiles confirm the gradient distribution of the sodium element in Na-doped absorbers. Photoluminescence spectra show that the introduction of appropriate sodium into the absorber can inhibit the band tail states. As high as 11.18% of power conversion efficiency (PCE) is achieved for the device treated with 5 mg mL-1 NaCl solution, and an average efficiency of Na-doped devices is 10.71%, 13% higher than that of the control groups (9.45%). Besides, the depletion width and the charge recombination lifetime can also have regular variation with sodium treatment. This work offers an easy modification method for high-quality Na-doped CZTSSe films and high-performance devices, in the meantime, it can also help to further understand the effects of sodium in CZTSSe solar cells.

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Enhanced electrodeposition and separation of metallic Cr from soluble K2CrO4 on a liquid Zn cathode Wei Weng, Zhi Wang, Zhancheng Guo, Shuqiang Jiao, Mingyong Wang 2020, 40(1): 204-211.  DOI: 10.1016/j.jechem.2019.04.021 摘要 ( 3 )   Carbon contamination and the formation of low-valence oxides limit the preparation of refractory metals by molten salt electrolysis. In this paper, a liquid Zn cathode is adopted for the electrochemical reduction of soluble K2CrO4 to metallic Cr in CaCl2-KCl molten salt. It is found that CrO42- can be directly electrochemically reduced to Cr via a six-electron-transfer step and low-valence Cr oxides is hardly produced. The reduction rate is obviously increased from 16.7 mgCr h-1 cm-2 on the solid Mo cathode to 58.7 mgCr h-1 cm-2 on liquid Zn cathode. The electrodeposited Cr is distributed in liquid Zn cathode. Carbon contamination is effectively avoided due to the negligible solubility of carbon in the liquid Zn cathode. Furthermore, Cr can be effectively separated and enriched to the bottom of liquid Zn under supergravity field, realizing the efficient acquisition of metallic Cr and recycling of liquid Zn. The method herein provides a promising route for the preparation of refractory metals with high-purity by molten salt electrolysis.

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Surface interaction between Pd and nitrogen derived from hyperbranched polyamide towards highly effective formic acid dehydrogenation Yancun Yu, Xian Wang, Changpeng Liu, Fateev Vladimir, Junjie Ge, Wei Xing 2020, 40(1): 212-216.  DOI: 10.1016/j.jechem.2019.04.017 摘要 ( 4 )   Hydrogen production from formic acid decomposition (FAD) is a promising means of hydrogen energy storage and utilization in fuel cells. Development of efficient catalysts for dehydrogenation of formic acid is a challenging topic. The surface chemical and electronic structure of the active catalysis components is important in formic acid decomposition at room-temperature. Here, the pyrdinic-nitrogen doped catalysts from hyperbranched polyamide were prepared via in situ polymerization reaction process by using activated carbon as a support. Because of the introduction of the polymer, the particles of the catalysts were stabilized, and the average particle diameter was only 1.64 nm. Under mild conditions, the catalysts activities were evaluated for FAD. The optimized Pd-N30/C catalyst exhibited high performance achieving almost full conversion, with a turnover frequency of 3481 h-1 at 30℃.

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Heat treatment bimetallic PdAu nanocatalyst for oxygen reduction reaction Qingyun Hu, Wei Zhan, Yifei Guo, Laiming Luo, Ronghua Zhang, Di Chen, Xinwen Zhou 2020, 40(1): 217-223.  DOI: 10.1016/j.jechem.2019.05.011 摘要 ( 12 )   Pd-based nanocatalyst is a potential oxygen reduction oxidation (ORR) catalyst because of its high activity in alkaline medium and low cost. In this work, bimetallic PdAu nanocatalysts are prepared by one-pot hydrothermal method using triblock pluronic copolymers, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO19-PPO69-PEO19)(P123) as reducer and stabilizer, and heat-treatment method is applied to regulate catalyst structure and improve catalyst activity. The results show that the heat treatment can agglomerate the catalyst to a certain extent, but effectively improve the crystallinity and alloying degree of the catalyst. The ORR performance of the PdAu nanocatalysts obtained under different heat treatment conditions is systematically investigated. Compared with commercial Pd black and PdAu catalyst before heat treatment, the ORR performance of AuPd nanocatalyst obtained after heat treatment for one hour at 500℃ has been enhanced. The PdAu nanocatalysts after heat treatment also display enhanced anti-methanol toxicity ability in acidic medium.

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Corrigendum to “Preparation of high-purity straight silicon nanowires by molten salt electrolysis” [Journal of Energy Chemistry 40 (2020) 171-179] Jie Zhang, Sheng Fang, Xiaopeng Qi, Zhanglong Yu, Zhaohui Wu, Juanyu Yang, Shigang Lu 2020, 40(1): 224-224.  DOI: 10.1016/j.jechem.2019.08.004 摘要 ( 7 )