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2019, Vol. 38, No. 11　Online: 2019-11-15

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Obituary for Dang Sheng Su Xinhe Bao, Qiang Zhang 2019, 38(11): 0-0.  DOI: 10.1016/S2095-4956(19)30728-4 摘要 ( 4 )

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In Memoriam: Dang Sheng Su (1961-2019) Gabriele Centi 2019, 38(11): 0-0.  DOI: 10.1016/S2095-4956(19)30729-6 摘要 ( 0 )

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Investigation of Li-ion transport in Li7P3S11 and solid-state lithium batteries Chuang Yu, Swapna Ganapathy, Ernst R. H. van Eck, Lambert van Eijck, Niek de Klerk, Erik M. Kelder, Marnix Wagemaker 2019, 38(11): 1-7.  DOI: 10.1016/j.jechem.2018.12.017 摘要 ( 29 )   The high Li-ion conductivity of the Li7P3S11 sulfide-based solid electrolyte makes it a promising candidate for all-solid-state lithium batteries. The Li-ion transport over electrode-electrolyte and electrolyteelectrolyte interfaces, vital for the performance of solid-state batteries, is investigated by impedance spectroscopy and solid-state NMR experiments. An all-solid-state Li-ion battery is assembled with the Li7P3S11 electrolyte, nano-Li2S cathode and Li-In foil anode, showing a relatively large initial discharge capacity of 1139.5 mAh/g at a current density of 0.064 mA/cm2 retaining 850.0 mAh/g after 30 cycles. Electrochemical impedance spectroscopy suggests that the decrease in capacity over cycling is due to the increased interfacial resistance between the electrode and the electrolyte. 1D exchange 7Li NMR quantifies the interfacial Li-ion transport between the uncycled electrode and the electrolyte, resulting in a diffusion coefficient of 1.70(3)×10-14 cm2/s at 333 K and an energy barrier of 0.132 eV for the Li-ion transport between Li2S cathode and Li7P3S11 electrolyte. This indicates that the barrier for Li-ion transport over the electrode-electrolyte interface is small. However, the small diffusion coefficient for Li-ion diffusion between the Li2S and the Li7P3S11 suggests that these contact interfaces between electrode and electrolyte are relatively scarce, challenging the performance of these solid-state batteries.

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Core-branch CoNi hydroxysulfides with versatilely regulated electronic and surface structures for superior oxygen evolution electrocatalysis Bin Wang, Cheng Tang, Hao-Fan Wang, Xiao Chen, Rui Cao, Qiang Zhang 2019, 38(11): 8-14.  DOI: 10.1016/j.jechem.2018.12.006 摘要 ( 6 )   To satisfy the rapid development of gas-involving electrocatalysis (O2, CO2, N2, etc.), nanostructured electrocatalysts with favorably regulated electronic structure and surface nanostructures are urgently required. Herein, we highlighted a core-branch hydroxysulfide as a significantly enhanced oxygen evolution reaction electrocatalyst. This hydroxysulfide was facilely fabricated via a versatile interfacial reaction in S2- inorganic solution at room temperature for a designed period. The moderative growth kinetics contributed to the growth of interconnected hydroxysulfide nanosheets with high-sulfur contents on the hydroxide precursor substrates, resulting in a hierarchical nanostructure with multifunctional modifications, including regulated electronic structure, rapid electron highway, excellent accessibility, and facilitated mass transfer. Such synthetic methodology can be generalized and facilely governed by regulating the temperature, concentration, duration, and solvent for targeted nanostructures. Contributed to the favorably regulated electronic structure and surface nanostructure, the as-obtained core-branch Co2NiS2.4(OH)1.2 sample exhibits superior OER performance, with a remarkably low overpotential (279 mV required for 10.0 mA cm-2), a low Tafel slope (52 mV dec-1), and a favorable long-term stability. This work not only presents a promising nanostructured hydroxysulfide for excellent OER electrocatalysis, but also shed fresh lights on the further rational development of efficient electrocatalysts.

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Revealing the roles of components in glucose selective hydrogenation into 1,2-propanediol and ethylene glycol over Ni-MnOx-ZnO catalysts Yifan Zan, Gai Miao, Hao Wang, Lingzhao Kong, Yaping Ding, Yuhan Sun 2019, 38(11): 15-19.  DOI: 10.1016/j.jechem.2018.12.016 摘要 ( 8 )   MnOx-promoted Ni-based catalyst supported by ZnO was developed to selectively hydrogenate glucose into polyols in water at 523 K with a yield of 64.9%. Using glucose, sorbitol, glycerol and LA as the rawmaterials, the roles of nickel, ZnO and MnOx were investigated. The results show that nickel provided a new pathway of glucose to sorbitol and played an important role in the hydrogenation of C3 intermediates to 1,2-propanediol (1,2-PDO). The high yield of 1, 2-PDO was attributed to effective C-C bond cleavage performance of ZnO support promoted by MnOx. ZnO and MnOx contribute to the conversion of glycerol to lactic acid (LA) and LA to 1, 2-PDO, respectively. A concise pathway for hydrogenation of glucose over Ni-based catalyst was proposed.

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Porous V2O5 nanofibers as cathode materials for rechargeable aqueous zinc-ion batteries Xuyong Chen, Liubin Wang, Hang Li, Fangyi Cheng, Jun Chen 2019, 38(11): 20-25.  DOI: 10.1016/j.jechem.2018.12.023 摘要 ( 25 )   Rechargeable aqueous zinc-ion batteries are recently gaining incremental attention because of low cost and material abundance, but their development is plagued by limited choice of cathode materials with satisfactory cycling performance. Here, we report a porous V2O5 nanofibers cathode with high Znstorage performance in an aqueous Zn(CF3SO3)2 electrolyte. We propose a reaction mechanism based on phase transition from orthorhombic V2O5 to zinc pyrovanadate on first discharging and reversible Zn2+ (de)intercalation in the open-structured hosts during subsequent cycling. This open and stable architecture enables a high reversible capacity of 319 mAh g-1 at 20 mA g-1 and a capacity retention of 81% over 500 cycles. The remarkable electrochemical performance makes V2O5 a promising cathode for aqueous zinc-ion batteries.

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Phase control of 2D binary hydroxides nanosheets via controllingrelease strategy for enhanced oxygen evolution reaction and supercapacitor performances Min Wei, Jing Li, Wei Chu, Ning Wang 2019, 38(11): 26-33.  DOI: 10.1016/j.jechem.2019.01.003 摘要 ( 3 )   An OH--slow-release strategy was established to controllably tune the (α- and β-) phase of nickel cobalt binary hydroxide in the presence of ammonium chloride. Ammonium chloride is added to the ionic solution to regulate the pH of the solution and slow down the release of OH-, effectively regulating the phase, nanostructure, interlayer spacing, surface area, thickness, and the performance of binary Ni-Co hydroxide. The ion-slow-release mechanism is conducive to the formation of α-phase with larger interlayer spacing and thinner flakes rather than β-phase. Attributed to the enlarged interlayer spacing, thinner nanosheets, and more exposed active sites, the resultant α-phase hydroxides (NCNS-5.2), displayed much lower over potential of 285 mV with respect to the dense-stacked β-phase hydroxides (362 mV) for OER at 10 mA/cm2. It also exhibited high specific capacitance of 1474.2 F/g, when tested at 0.5 A/g within a voltage range of 0-0.45 V vs. Hg/HgO. This composite was also stable for water oxidation reaction and supercapacitor. The proof-of-concept of using controlled-release agent may provide suggestive insights for the material innovation and a variety of applications.

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Rechargeable Zn-air batteries initiated by nickel-cobalt bimetallic selenide Changqi Sun, Xiaosong Guo, Jingyan Zhang, Genliang Han, Daqiang Gao, Xiaoping Gao 2019, 38(11): 34-40.  DOI: 10.1016/j.jechem.2019.01.001 摘要 ( 1 )   A Zn-air battery is a potential next-generation energy storage device owing to its extremely high theoretical energy density. Currently, it is important to explore non-precious metal electrocatalysts with high electroactivity and stability in the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for the development of Zn-air batteries. In this work, porous (Ni,Co)Se2 nanosheets were synthesized by selenizing NiCo2O4 nanosheets. By regulating the conductivity and morphology of the sample, the prepared porous (Ni,Co)Se2 nanosheets show enhanced electrocatalytic activity for OER and ORR compared to NiCo2O4 nanosheets. The aqueous Zn-air battery using porous (Ni,Co)Se2 nanosheets as the air cathode exhibits superior charge and discharge performance (1.98 V for charging and 1.17 V for discharging), high specific capacity (770 mAh/g), and excellent cycle stability (140 h). These results indicate that the porous (Ni,Co)Se2 nanosheets are suitable as a bifunctional electrocatalyst for future Zn-air batteries.

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Transition metal nanoparticles supported La-promoted MgO as catalysts for hydrogen production via catalytic decomposition of ammonia Xiu-Cui Hu, Wei-Wei Wang, Zhao Jin, Xu Wang, Rui Si, Chun-Jiang Jia 2019, 38(11): 41-49.  DOI: 10.1016/j.jechem.2018.12.024 摘要 ( 58 )   The uniformly dispersed transition metal (Co, Ni and Fe) nanoparticles supported on the surface of La-promoted MgO were prepared via a deposition-precipitation method for hydrogen production from catalytic decomposition of ammonia. X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, temperature-programmed reduction and temperature-programmed desorption were used to investigate the structure-activity relation of catalysts in NH3 decomposition. The results show that the strong interaction between active species and support can effectively prevent the active species from agglomerating during ammonia decomposition reaction. In addition, the introduction of La species not only facilitates the adsorption and decomposition of NH3 and desorption of N2, but also benefits the better dispersion of the active species. The prepared catalysts showed very high catalytic activity for ammonia decomposition compared with the same active composition samples that reported previously. Meanwhile, the catalysts showed excellent high-temperature stability and no any deactivation was observed, which are very promising candidates for the decomposition of ammonia to hydrogen.

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Employing MXene as a matrix for loading amorphous Si generated upon lithiation towards enhanced lithium-ion storage Haojie Li, Ming Lu, Wenjuan Han, Haibo Li, Yucheng Wu, Wei Zhang, Jiaheng Wang, Bingsen Zhang 2019, 38(11): 50-54.  DOI: 10.1016/j.jechem.2018.12.020 摘要 ( 11 )   Although Si-based nanomaterials provide incomparable lithium ion storage ability in theory, it suffers from low initial Coulombic efficiency, electrical disconnection, and fracture due to huge volume changes after extended cycles. As a result, it leads to a severe capacity fading and an increase in internal impedance. Herein, Ti-elemental MXene was employed as a matrix for the intermediate product of Si electrodes. The boundary between the inner core of pristine Si and its outer shell of amorphous LixSi alloy was reconstructed. Smaller amorphous aggregates were observed in the MXene&Si hybrid electrode after 500 cycles by using transmission electron microscopy. Consequently, an enhanced specific capacity was achieved as MXene as a matrix enables loading amorphous Si.

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Self-assembly synthesis of solid polymer electrolyte with carbonate terminated poly(ethylene glycol) matrix and its application for solid state lithium battery Bing Yuan, Guangmei Luo, Jing Liang, Fangyi Cheng, Wangqing Zhang, Jun Chen 2019, 38(11): 55-59.  DOI: 10.1016/j.jechem.2019.01.004 摘要 ( 7 )   A facile one-pot synthesis of solid polymer electrolytes (SPEs), composed of carbonate terminated poly(ethylene glycol) (CH3O-PEG-IC), poly(ethylene glycol)-block-polystyrene (PEG-b-PS) block copolymer nanoparticles containing a conductive PEG corona, fumed SiO2 and LiTFSI salt via polymerization-induced self-assembly is proposed. This method to prepare SPEs has the advantages of one-pot convenient synthesis, avoiding use of organic solvent and conveniently adding inorganic additives. CH3O-PEG-IC combines advantages of PEG and polycarbonate, the in situ synthesized PEG-b-PS nanoparticles containing a rigid polystyrene (PS) core and a PEG corona guarantee continuous lithium ion transport in the synthesized SPEs, and the fumed SiO2 optimizes the interfacial properties and improves the electrochemical stability, all of which afford SPEs a well considerable room temperature ionic conductivity of 1.73×10-4 S/cm, high lithium transference number of 0.53, and wide electrochemical stability window of 5.5 V (vs. Li+/Li). By employing these SPEs, the assembled solid state cells of LiFePO4|SPEs|Li exhibit considerable cell performance.

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Controllable active sites and facile synthesis of cobalt nanoparticle embedded in nitrogen and sulfur co-doped carbon nanotubes as efficient bifunctional electrocatalysts for oxygen reduction and evolution reactions Taeseob Oh, Kwanwoo Kim, Jooheon Kim 2019, 38(11): 60-67.  DOI: 10.1016/j.jechem.2018.12.021 摘要 ( 6 )   Development of efficient and promising bifunctional electrocatalysts for oxygen reduction and evolution reactions is desirable. Herein, cobalt nanoparticles embedded in nitrogen and sulfur co-doped carbon nanotubes (Co@NSCNT) were prepared by a facile pyrolytic treatment. The cobalt nanoparticles and codoping of nitrogen and sulfur can improve the electron donor-acceptor characteristics of the carbon nanotubes and provide more active sites for catalytic oxygen reduction and evolution reactions. The prepared Co@NSCNT, annealed at 900℃, showed excellent electrocatalytic performance and better durability than commercial platinum catalysts. Additionally, Co@NSCNT-900 catalysts exhibited comparable onset potentials and Tafel slopes to ruthenium oxide. Overall, Co@NSCNT showed high activity and improved durability for both oxygen evolution and reduction reactions.

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Facile synthesis of Mo2C nanoparticles on N-doped carbon nanotubes with enhanced electrocatalytic activity for hydrogen evolution and oxygen reduction reactions Yue-Jun Song, Jin-Tao Ren, Gege Yuan, Yali Yao, Xinying Liu, Zhong-Yong Yuan 2019, 38(11): 68-77.  DOI: 10.1016/j.jechem.2019.01.002 摘要 ( 2 )   Developing low-cost and highly-efficient electrocatalysts for renewable energy conversion technologies has attracted even-increasing attention. Molybdenum carbide materials have recently emerged as a type of promising catalysts for electrocatalytic reactions due to the earth-abundance and Pt-resembled electrical properties. In this work, taking the advantage of the interaction between the basic groups of the Mo(VI)-melamine polymer and the acidic groups on the surface of the oxidized carbon nanotubes (CNTs), N-doped CNTs supported Mo2C nanoparticles (Mo2C/NCNT) are prepared, which exhibit outstanding electrocatalytic activity and durability for both the hydrogen evolution and oxygen reduction reactions. The impressive performance of Mo2C/NCNT can be attributed to the small size of Mo2C particles, the large exposure ratio of surface sites and the presence of N-doped CNTs. This work enlarges the multi-field applications of molybdenum carbide-base materials as promising non-precious metal electrocatalysts, which is of great significance for sustainable energy-related technologies.

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A novel on-line electrochemical transmission infrared spectroscopy to study the current efficiency of carbonates for ethanol oxidation reactions in alkaline media Wei Peng, Li Xiao, Juntao Lu, Lin Zhuang 2019, 38(11): 78-83.  DOI: 10.1016/j.jechem.2019.01.008 摘要 ( 0 )   Research on the reaction mechanism of ethanol oxidation reaction (EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis of the non-volatile products. Conventional on-line electrochemical flowing transmission infrared spectroscopy (ETIRS) can only collect a part of the carbonate products of EOR in alkaline media, making the further quantitative study impossible. Herein, a new ETIRS system has been designed and prepared by employing a cation-exchange membrane (Nafion) in the sampling hood. The using of the Nafion membrane can prevent the anions crossing over by confining the generated carbonates in the sampling hood without diffusing into the bulk electrolyte. Therefore, the collection efficiency of the carbonate products as well as the test accuracy of the carbonate current efficiency has been significantly improved. The result of CO stripping reaction shows that ca. 100% of the carbonate product is able to be collected in alkaline media by this new system. The influence of the experimental temperature to the carbonate current efficiency has been further studied on Pt/C toward EOR in alkaline media.

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Lithium ion conductivity of complex hydrides incorporating multiple closo-type complex anions Naoki Toyama, Sangryun Kim, Hiroyuki Oguchi, Toyoto Sato, Shigeyuki Takagi, Masaru Tazawa, Genki Nogami, Shin-ichi Orimo 2019, 38(11): 84-87.  DOI: 10.1016/j.jechem.2019.01.009 摘要 ( 5 )   We report the lithium ionic conductivities of closo-type complex hydrides synthesized from various molar ratios of lithium borohydride (LiBH4) and decaborane (B10H14) as starting materials. The prepared closo-type complex hydrides comprised[B12H12]2-,[B11H11]2-, and[B10H10]2- complex anions. In addition, increasing the LiBH4 content in the starting materials increased the amounts of[B11H11]2- and[B10H10]2-, leading to an improved ion conductivity of the prepared sample. The present study offers useful insights into strategies for controlling the complex anion composition in emerging solid electrolytes of closo-type complex hydrides at the molecular level, and improving their ionic conductivities.

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Chlorophyll-based organic solar cells with improved power conversion efficiency Shenghan Wang, Shengnan Duan, Yuwei Wang, Chenglin Sun, Xiao-Feng Wang, Shin-ichi Sasaki 2019, 38(11): 88-93.  DOI: 10.1016/j.jechem.2018.12.018 摘要 ( 22 )   Chlorophylls (Chls), and associated chlorophyll derivatives, are one of the oldest, most versatile organic semiconductors found in nature. Herein, we present two easily semi-synthesized chlorophyll derivatives, namely, chlorin e6 trimethyl ester (Ce6Me3) and its copper complex (Cu-Ce6Me3), as the p-type dopants for organic semiconductors and their impact in organic solar cells (OSCs). In our study, both Chls showed intense Soret and Qy bands in the UV-visible spectra, leading to an effect means for capturing solar light and energy. Chls also exhibited high carrier mobility owing to the partial formation of aggregates through the spin-coating process. Using Chls, we fabricated OSCs in both planar-heterojunction (PHJ) and bulkheterojunction (BHJ) solar cell configurations, together with C70/PC70BM as electron acceptors. In PHJ solar cells, we received solar power conversion efficiencies (PCEs) of only 0.85% and 0.93% for Cu-Ce6Me3- and Ce6Me3-based devices, respectively, with the thickness of the donor layer at 5 nm. In BHJ cells, we achieved much higher PCEs of 1.53% and 2.05% for Cu-Ce6Me3:PC70BM and Ce6Me3:PC70BM respectively, where both blending ratios were set to 1:8. The improvement on PCE in BHJ cells may be attributed to the better charge separation increase at the donor-acceptor interface.

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Carbon-based derivatives from metal-organic frameworks as cathode hosts for Li-S batteries Qingping Wu, Xuejun Zhou, Jun Xu, Fahai Cao, Chilin Li 2019, 38(11): 94-113.  DOI: 10.1016/j.jechem.2019.01.005 摘要 ( 19 )   Lithium-sulfur batteries (Li-S batteries) are promising candidates for the next generation high-energy rechargeable Li batteries due to their high theoretical specific capacity (1672 mAh g-1) and energy density (2500 Wh kg-1). The commercialization of Li-S batteries is impeded by several key challenges at cathode side, e.g. the insulating nature of sulfur and discharged products (Li2S2 and Li2S), the solubility of long-chain polysulfides and volume variation of sulfur cathode upon cycling. Recently, the carbonbased derivatives from metal-organic frameworks (MOFs) has emerged talent in their utilization as cathode hosts for Li-S batteries. They are not only highly conductive and porous to enable the acceleration of Li+/e- transfer and accommodation of volumetric expansion of sulfur cathode during cycling, but also enriched by controllable chemical active sites to enable the adsorption of polysulfides and promotion of their conversion reaction kinetics. In this review, based on the types of MOFs (e.g. ZIF-8, ZIF-67, Prussian blue, Al-MOF, MOF-5, Cu-MOF, Ni-MOF), the synthetic methods, formation process and morphology, structural superiority of MOFs-derived carbon frameworks along with their electrochemical performance as cathode host in Li-S batteries are summarized and discussed.

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ZrO2 nanoparticles anchored on nitrogen-doped carbon nanosheets as efficient catalyst for electrochemical CO2 reduction Zhengpei Miao, Pei Hu, Chuanye Nie, Huan Xie, Wenli Fu, Qing Li 2019, 38(11): 114-118.  DOI: 10.1016/j.jechem.2019.01.010 摘要 ( 7 )   Electrochemical reduction of CO2 to produce value-added feedstock chemicals using high-performance electrocatalysts is a promising protocol to address the excessive CO2 in the atmosphere and the energy crisis. However, the high overpotential, low current density, and poor product selectivity for CO2 electroreduction greatly impede their practical applications. In this work, we develop an efficient catalyst for CO2 reduction to CO consisting of well-dispersed ZrO2 nanoparticles tightly anchored on nitrogendoped carbon nanosheets (ZrO2/N-C) for the first time. Importantly, the ZrO2 nanoparticles possess oxygen vacancies and defects, which regulate the electronic structure of catalyst and thus greatly enhance the electrocatalytic activity. Specifically, ZrO2/N-C demonstrates a high CO Faradaic efficiency (FE) of 64% at -0.4 V vs. the reversible hydrogen electrode (RHE) and a respectable current density of ~2.6 mA cm-2 in CO2-saturated 0.5 M KHCO3 solution. This work opens a new avenue for developing excellent catalysts for CO2 electroreduction with metal oxide/heteroatom-doped carbon composite structure.

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Combination-based nanomaterial designs in single and double dimensions for improved electrodes in lithium ion-batteries and faradaic supercapacitors Tuyet Nhung Pham, Duckshin Park, Yongil Lee, Il Tae Kim, Jaehyun Hur, You-Kwan Oh, Young-Chul Lee 2019, 38(11): 119-146.  DOI: 10.1016/j.jechem.2018.12.014 摘要 ( 4 )   In the past decade, researchers in the fields of energy production have concentrated on the improvement of new energy storage devices. Lithium-ion batteries (LIBs) and faradaic supercapacitors (FSs) have attracted special attention as a result of the rapid development of new electrode nanomaterials, especially hybrid nanomaterials, which can meet the increasingly higher requirements for future energy, such as the capability to deliver high-power performance and an extremely long life cycle. In these hybrid nanostructures, a series of synergistic effects and unique properties arising from the combination of individual components are a major factor leading to improved charge/discharge capability, energy density, and system lifetime. This paper describes the most recent progress in the growth of hybrid electrode materials for LIBs and FSs systems, focusing on the combination of zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) nanomaterials, respectively.

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Selenium cooperated polysulfide electrolyte for efficiency enhancement of quantum dot-sensitized solar cells Mengsi Zhou, Gencai Shen, Zhenxiao Pan, Xinhua Zhong 2019, 38(11): 147-152.  DOI: 10.1016/j.jechem.2018.12.010 摘要 ( 15 )   The modification of polysulfide electrolyte with additives has been demonstrated as an effective way to improve the photovoltaic performance of quantum dot-sensitized solar cells (QDSCs). Most of these additives can inhibit the charge recombination processes at photoanode/electrolyte interface and favor the improvement of Voc of cell devices. Herein, we showed that the incorporation of elemental selenium (Se) in polysulfide electrolyte to form polyselenosulfide species can notably improve the performance of QDSCs. Unlike previous reports, we present here an integrated investigation of the effects of polyselenosulfide species in polysulfide electrolyte on the photovoltaic performance of QDSCs from both of the photoanode and counter electrode (CE) aspects. Electrochemical impedance spectroscopy (IS) and opencircuit voltage-decay (OCVD) measurements demonstrated that the introduction of Se into polysulfide electrolyte can not only retard charge recombination at photoanode/electrolyte interface, but also reduce the charge transfer resistance at CE/electrolyte interface, resulting in the improvement of Jsc and FF values. Consequently, the average efficiency of Zn-Cu-In-Se QDSCs was improved from 9.26% to 9.78% under AM 1.5 G full one sun illumination.

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Ultrafine polycrystalline titania nanofibers for superior sodium storage Zhidan Diao, Daming Zhao, Chunxiao Lv, Hongli Liu, Dongjiang Yang, Shaohua Shen 2019, 38(11): 153-161.  DOI: 10.1016/j.jechem.2018.12.009 摘要 ( 7 )   Sodium ion batteries have a huge potential for large-scale energy storage for the low cost and abundance of sodium resources. In this work, a novel structure of ultrafine polycrystalline TiO2 nanofibers is prepared on nickel foam/carbon cloth by a simple vapor deposition method. The as-prepared TiO2 nanofibers show excellent performance when used as anodes for sodium-ion batteries. Specifically, the TiO2 nanofibers@nickel foam electrode delivers a high reversible capacity of 263.2 mAh g-1 at 0.2 C and maintains a considerable capacity of 144.2 mAh g-1 at 10 C. The TiO2 nanofibers@carbon cloth electrode also shows excellent high-rate capability, sustaining a capacity of 148 mAh g-1 after 2000 cycles at 10 C. It is believed that the novel nanofibrous structure increases the contact area with the electrolyte and greatly shortens the sodium ion diffusion distance, and meanwhile, the polycrystalline nature of nanofibers exposes more intercalation sites for sodium storage. Furthermore, the density functional theory calculations exhibit strong ionic interactions between the exposed TiO2 (101) facets and sodium ions, leading to a preferable sodiation/desodiation process. The unique structural features endow the TiO2 nanofibers electrodes great advantages in rapid sodium storage with an outstanding high-rate capability.

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Hydrogen generation with acid/alkaline amphoteric water electrolysis Qing Lei, Baoguo Wang, Peican Wang, Shuai Liu 2019, 38(11): 162-169.  DOI: 10.1016/j.jechem.2018.12.022 摘要 ( 67 )   To reduce the energy consumption of the electrolytic hydrogen generation process, we propose a novel approach to generate hydrogen with acidic/alkaline amphoteric water electrolysis, wherein hydrogen is produced inside an acidic solution and oxygen evolved under alkaline condition, and a membrane is employed in the middle of the electrolyzer to restrain neutralization. The electrode polarization is greatly reduced due to the specific arrangement of the acidic/alkaline amphoteric electrolyzer. The rate of hydrogen production achieves over four times higher than that of the alkaline aqueous solution at 2.2 V, and the energy consumption is reduced approximately 30% under the current density of 200 mA/cm2. The investigation of transmembrane potential drop indicates water splitting on the membrane surfaces, which compensates for acid or alkaline loss on-site and maintains the concentration approximately constant during electrolysis process. The acidic/alkaline amphoteric water electrolysis is promising as an energy saving, clean and sustainable hydrogen production technology.

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In-situ embedding zeolitic imidazolate framework derived Co-N-C bifunctional catalysts in carbon nanotube networks for flexible Zn-air batteries Bo Lv, Sha Zeng, Wei Yang, Jian Qiao, Chao Zhang, Chengfeng Zhu, Minghai Chen, Jiangtao Di, Qingwen Li 2019, 38(11): 170-176.  DOI: 10.1016/j.jechem.2019.04.005 摘要 ( 16 )   Recently, the development of high-performance bifunctional oxygen catalysts integrated with flexible conductive scaffolds for rechargeable metal-air batteries has attracted considerable interest, driving by fastgrowing wearable electronics. Herein, we report a flexible bifunctional oxygen catalyst thin film consisting of Co-N-C bifunctional catalysts embedding in carbon nanotube (CNT) networks. The catalyst is readily prepared by pyrolysis of cobalt-based zeolitic imidazolate frameworks (ZIF-67) that are in-situ synthesized in CNT networks. Such catalyst film demonstrates very high catalytic activities for oxygen reduction (onset potential:0.91 V, and half-wave potential:0.87 V vs. RHE) and oxygen evolution (10 mA cm-2 at 1.58 V) reactions, high methanol tolerance property, and long-term stability (97% current retention). Moreover, our integrated catalyst film shows very good structure flexibility and robustness. Based on the obtained film air electrodes, flexible Zn-air batteries demonstrate low charging and discharging overpotentials (0.82 V at 1 mA cm-1) and excellent structure stability in the bending tests. These results indicate that presently reported catalyst films are potential air electrodes for flexible metal-air batteries.

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Theoretical assessment of hydrogen production and multicycle energy conversion via solar thermochemical cycle based on nonvolatile SnO2 Mingkai Fu, Huajun Xu, Haitao Ma, Xin Li 2019, 38(11): 177-184.  DOI: 10.1016/j.jechem.2019.03.035 摘要 ( 3 )   A kind of solar thermochemical cycle based on methanothermal reduction of SnO2 is proposed for H2 and CO production. We find that the oxygen release capacity and thermodynamic driven force for methanothermal reduction of SnO2 are large, and suggest CH4:SnO2=2:1 as the feasible reduction condition for achieving high purities of syngas and avoiding vaporization of produced Sn. Subsequently, the amount of H2 and energetic upgrade factors under different oxidation conditions are compared, in which excess water vapor is found beneficial for hydrogen production and fuel energetic upgradation. Moreover, the effect of incomplete recovery of SnO2 on the subsequent cycle is underscored and explained. After accounting for factors such as isothermal operation and cycle stability, CH4:SnO2=2:1 and H2O:Sn=4:1 are suggested for highest solar-to-fuel efficiency of 46.1% at nonisothermal condition, where the reduction and oxidation temperature are 1400 and 600 K, respectively.

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Na2V6O16·2.14H2O nanobelts as a stable cathode for aqueous zinc-ion batteries with long-term cycling performance Fang Hu, Di Xie, Depeng Zhao, Guihong Song, Kai Zhu 2019, 38(11): 185-191.  DOI: 10.1016/j.jechem.2019.03.036 摘要 ( 6 )   Aqueous zinc-ion batteries (ZIBs) have been considered as one of the most promising electrochemical devices for large-scale energy storage system owing to their low cost and high safety. Herein, Na2V6O16·2.14H2O nanobelts are synthesized and applied as cathode material for ZIBs. The sample displays a high capacity of 466 mAh g-1 at 100 mA g-1 and stable cycling performance with a capacity retention of 90% over 2000 cycles at the 20 A g-1. Moreover, Na2V6O16·2.14H2O presents a capable rate ability and a high energy density of 312 Wh kg-1 at a specific power of 70 W kg-1. The superior electrochemical performance is attributed to the large interlayer spacing and outstanding structure stability, which promise the highly reversible intercalation and extraction of zinc ion. The electrochemical kinetics and zinc ion storage mechanism are also investigated. This work demonstrates that nanoscale electrode materials with large interlayer spacing can effectively enhance the electrochemical performance of aqueous ZIBs, which can be extended to other metal ion batteries, such as magnesium ion batteries and aluminum ion batteries.

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The fabrication of homogeneous perovskite films on non-wetting interfaces enabled by physical modification Jiang You, Fei Guo, Shudi Qiu, Wenxin He, Chuan Wang, Xianhu Liu, Weijian Xu, Yaohua Mai 2019, 38(11): 192-198.  DOI: 10.1016/j.jechem.2019.03.033 摘要 ( 73 )   Conjugated polymers are commonly used as effective hole transport materials (HTMs) for preparation of high-performance perovskite solar cells. However, the hydrophobic nature of these materials renders it difficult to deposit photovoltaic perovskite layers on top via solution processing. In this article, we report a generic surface modification strategy that enables the deposition of uniform and dense perovskite films on top of non-wetting interfaces. In contrast to the previous proposed chemical modifications which might alter the optoelectronic properties of the interfacial layers, we realized a nondestructive surface modification enabled by introducing a layer of insulating mesoporous aluminum oxide (Al2O3). The surface energies of the typical non-wetting hole-transport layers (PTAA, P3HT, and Poly-TPD) were significantly reduced by the Al2O3 modification. Benefiting from the intact optoelectronic properties of the HTMs, perovskite solar cells deposited on these interface materials show full open-circuit voltages (VOC) with high fill factors (FF) up to 80%. Our method provides an effective avenue for exploiting the full potential of the existing as well as newly developed non-wetting interface materials for the fabrication of high-performance inverted perovskite solar cells.

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Large-scale fabrication of reduced graphene oxide-sulfur composite films for flexible lithium-sulfur batteries Yue Liu, Minjie Yao, Linlin Zhang, Zhiqiang Niu 2019, 38(11): 199-206.  DOI: 10.1016/j.jechem.2019.03.034 摘要 ( 10 )   The rapid development of flexible electronic devices requires the design of flexible energy-storage devices. Lithium-sulfur (Li-S) batteries are attracting much interest due to their high energy density. Therefore, flexible Li-S batteries with high areal capacity are desired. Herein, we fabricated freestanding reduced graphene oxide-sulfur (RGO@S) composite films with a cross-linked structure using a blade coating technique, followed by a subsequent chemical reduction. The porous cross-linked structure endows the composite films with excellent electrochemical performance. The batteries based on RGO@S composite films could exhibit a high discharge capacity of 1381 mAh/g at 0.1 C and excellent cycle stability. Furthermore, the freestanding composite film possesses excellent conductivity and high mechanical strength. Therefore, they can be used as the cathodes of flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled and remained stable electrochemical performance under different bending states.

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Improvement on the performance of perovskite solar cells by doctor-blade coating under ambient condition with holetransporting material optimization Deng Wang, Jiming Zheng, Xingzhu Wang, Jishu Gao, Weiguang Kong, Chun Cheng, Baomin Xu 2019, 38(11): 207-213.  DOI: 10.1016/j.jechem.2019.03.023 摘要 ( 32 )   Numerous fabrication methods have been developed for high-efficiency perovskite solar cells (PSCs). However, these are limited to spin-coating processes in a glove box and are yet to be commercialized. Therefore, there is a need to develop a controllable and scalable deposition technique that can be carried out under ambient conditions. Even though the doctor-blade coating technique has been widely used to prepare PSCs, it is yet to be applied to high-efficiency PSCs under ambient conditions (RH~45%, RT~25℃). In this study, we conducted blade-coating fabrication of modified high-efficiency PSCs under such conditions. We controlled the substrate temperature to ensure phase transition of perovskite and added dimethyl sulfoxide (DMSO) to the perovskite precursor solution to delay crystallization, which can facilitate the formation of uniform perovskite films by doctor-blade coating. The as-prepared perovskite films had large crystal domains measuring up to 100 μm. Solar cells prepared from these films exhibited a current density that was enhanced from 17.22 to 19.98 mA/cm2 and an efficiency that was increased from 10.98% to 13.83%. However, the open-circuit voltage was only 0.908 V, probably due to issues with the hole-transporting layer. Subsequently, we replaced poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with NiOx as the hole-transporting material and then prepared higher-quality perovskite films by blade-coating under ambient conditions. The as-prepared perovskite films were preferably orientated and had large crystal domains measuring up to 200 μm; The open-circuit voltage of the resulting PSCs was enhanced from 0.908 to 1.123 V, while the efficiency increased from 13.83% to 15.34%.

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Mitigating self-discharge of carbon-based electrochemical capacitors by modifying their electric-double layer to maximize energy efficiency Yu-Zuo Wang, Xu-Yi Shan, Da-Wei Wang, Hui-Ming Cheng, Feng Li 2019, 38(11): 214-218.  DOI: 10.1016/j.jechem.2019.04.004 摘要 ( 11 )   Self-discharge is a significant issue in electric double layer energy storage, which leads to a rapid voltage drop and low energy efficiency. Here, we attempt to solve this problem by changing the structure of the electric double layer into a de-solvated state, by constructing a nano-scale and ion-conductive solid electrolyte layer on the surface of a carbon electrode. The ion concentration gradient and potential field that drive the self-discharge are greatly restricted inside this electric double layer. Based on this understanding, a high-efficiency graphene-based lithium ion capacitor was built up, in which the self-discharge rate is reduced by 50% and the energy efficiency is doubled. The capacitor also has a high energy density, high power output and long life, and shows promise for practical applications.

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Optimizing carbon/carbon supercapacitors in aqueous alkali sulfates electrolytes Qiang Gao 2019, 38(11): 219-224.  DOI: 10.1016/j.jechem.2019.03.037 摘要 ( 5 )   Neutral aqueous alkali sulfate has shown great interests for developing environmentally friendly high voltage and high energy supercapacitors. This work focuses on systematically investigating the properties of symmetric carbon/carbon supercapacitors in neutral aqueous alkali sulfates. At room temperature, the largest power and energy density were obtained with K2SO4 electrolyte due to the smallest cation dimensions and highest electrical conductivity. At low temperature, aqueous Li2SO4 electrolyte presents the best performance due to the largest solubility, allowing a long-term stability at temperatures ranging between 20℃ and -10℃ at a maximum voltage of 1.8 V. The excellent stability has been confirmed that capacitance retention achieves as high as 92% after 10,000 cycles. The capacitance variations with temperatures could essentially result from kinetic diffusion barrier, ion dimension changes and fewer pseudo-capacitance contributions under different temperatures. This work highlights the selected virtues of different alkali sulfate electrolytes for enhanced supercapacitors.