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2019, Vol. 39, No. 12　Online: 2019-12-15

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Microwave-assisted conversion of biomass wastes to pseudocapacitive mesoporous carbon for high-performance supercapacitor Xiangkun Bo, Kun Xiang, Yu Zhang, Yu Shen, Shanyong Chen, Yongzheng Wang, Mingjiang Xie, Xuefeng Guo 2019, 39(12): 1-7.  摘要 ( 15 )   Developing an efficient approach of transforming biomass waste to functional carbon-based electrode materials applied in supercapacitor offers an important and high value-added practical application due to the abundance and considerable low price of biomass wastes. Herein, a hierarchical carbon functionalized with electrochemical-active oxygen-containing groups was fabricated by microwave treatment from the biomass waste of camellia oleifera. The obtained mesoporous carbon (MAC) owns nanosheet morphology, rich mesoporosity, large surface area (1726 m2/g) and very high oxygenic functionalities (16.2 wt%) with pseudocapacitive activity. Prepared electrode of supercapacitor and tested in 2.0 M H2SO4, the MAC exhibits an obvious pseudocapacitive activity and achieved a superior supercapacitive performance to that of directly activated carbon (DAC-800) including high specific capacitance (367 F/g vs. 298 F/g) and better rate performance (66% vs. 44%). The symmetrical supercapacitor based on MAC shows a high capacity of 275 F/g, large energy density of 9.55 Wh/kg (at power density of 478 W/kg) and excellent cycling stability with 99% capacitance retention after 10000 continuous charge-discharge, endowing the obtained MAC a promising functional material for electrochemical energy storage.

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Preparation of dense Ta-LLZO/MgO composite Li-ion solid electrolyte: Sintering, microstructure, performance and the role of MgO Xiao Huang, Yang Lu, Zhen Song, Tongping Xiu, Michael E. Badding, Zhaoyin Wen 2019, 39(12): 8-16.  摘要 ( 35 )   Cubic phase Li7La3Zr2O12 (LLZO), a member of the Li-Garnet family, is a promising solid electrolyte and has been widely studied in recent years. However, LLZO samples prepared via conventional ambient air sintering reported in the published literature often contain large grains with lower than desired (<94%) relative density. In this study, a non-contact method of co-firing with mother powder method is proposed to prepare high-quality Ta-doped LLZO-MgO composite ceramics. By sintering at 1150℃ for 5 h, the ceramics can reach relative density of 98.2%, conductivity of 5.17×10-4 S cm-1 at 25℃ and fracture strength of ～150 MPa. The sintered samples have uniform fine-grained microstructure and high critical current densities of 0.75-0.95 mA cm-2 at room temperature in Li-Li symmetry cell with Au modification. In addition, systematic sintering experiments and characterizations are conducted to explore the function of MgO in inhibiting the Ta-LLZO grain growth and its existing form inside the composite ceramics.

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Towards full demonstration of high areal loading sulfur cathode in lithium-sulfur batteries Long Kong, Qi Jin, Xi-Tian Zhang, Bo-Quan Li, Jin-Xiu Chen, Wan-Cheng Zhu, Jia-Qi Huang, Qiang Zhang 2019, 39(12): 17-22.  摘要 ( 9 )   Lithium-sulfur (Li-S) batteries have been recognized as promising substitutes for current energy-storage technologies owing to their exceptional advantages in very high-energy density and excellent material sustainability. The cathode with high sulfur areal loading is vital for the practical applications of Li-S batteries with very high energy density. However, the high sulfur loading in an electrode results in poor rate and cycling performances of batteries in most cases. Herein, we used diameters of 5.0 (D5) and 13.0 (D13) mm to probe the effect of electrodes with different sizes on the rate and cycling performances under a high sulfur loading (4.5 mg cm-2). The cell with D5 sulfur cathode exhibits better rate and cycling performances comparing with a large (D13) cathode. Both the high concentration of lithium polysulfides and corrosion of lithium metal anode impede rapid kinetics of sulfur redox reactions, which results in inferior battery performance of the Li-S cell with large diameter cathode. This work highlights the importance of rational matching of the large sulfur cathode with a high areal sulfur loading, carbon modified separators, organic electrolyte, and Li metal anode in a pouch cell, wherein the sulfur redox kinetics and lithium metal protection should be carefully considered under the flooded lithium polysulfide conditions in a working Li-S battery.

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An effective oxygen electrode based on Ir0.6Sn0.4O2 for PEM water electrolyzers Guang Jiang, Hongmei Yu, Jinkai Hao, Jun Chi, Zhixuan Fan, Dewei Yao, Bowen Qin, Zhigang Shao 2019, 39(12): 23-28.  摘要 ( 26 )   An effective oxygen evolution electrode with Ir0.6Sn0.4O2 was designed for proton exchange membrane (PEM) water electrolyzers. The anode catalyst layer exhibits a jagged structure with smaller particles and pores, which provide more active sites and mass transportation channels. The prepared IrSn electrode showed a cell voltage of 1.96 V at 2.0 A cm-2 with Ir loading as low as 0.294 mg cm-2. Furthermore, IrSn electrode with different anode catalyst loadings was investigated. The IrSn electrode indicates higher mass current and more stable cell voltage than the commercial Ir Black electrode at low loading.

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Transformations of biomass-based levulinate ester into γ-valerolactone and pyrrolidones using carbon nanotubes-grafted N-heterocyclic carbene ruthenium complexes Qiujuan Shen, Yi Zhang, Yiping Zhang, Shaozao Tan, Jinzhu Chen 2019, 39(12): 29-38.  摘要 ( 0 )   As a renewable biomass-based compound with wide applications in food additives, fine chemical synthesis and fuels, γ-valerolactone (GVL) has attached much attention. While, pyrrolidones are widely used in pharmaceutical, agrochemical, material industrial and other chemical production. In this research, we demonstrated transformations of biomass-based ethyl levulinate (EL) into GVL and pyrrolidones by using heterogeneous catalysts (CNT-Ru-1) with N-heterocyclic carbene ruthenium (NHC-Ru) complex grafted on multi-walled carbon nanotube (CNT). The Ru catalyst showed high efficiency on EL hydrogenation to GVL with both EL conversion and GVL yield exceeding 99%. Moreover, the Ru catalyst readily promoted reductive amination of EL in the presence of various amines for pyrrolidone synthesis. Finally, the Ru catalyst was also applicable to hydrogenation of various carbonyl compounds for the synthesis of the corresponding alcohols with excellent catalytic performance. The research provides insight for heterogenizing the homogeneous noble metal-based catalysts with high catalytic active for biomass-based transformations.

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NiFe-based nanostructures on nickel foam as highly efficiently electrocatalysts for oxygen and hydrogen evolution reactions Wei Zhang, Daohao Li, Longzhou Zhang, Xilin She, Dongjiang Yang 2019, 39(12): 39-53.  摘要 ( 11 )   Water splitting, as an advanced energy conversion technology, consists of two half reactions, including oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the ideal electrocatalysts are noble metal based catalysts. Their high cost and scarcity in earth seriously restrict the large deployments. NiFe-based materials have attracted great attention in recent years due to their excellent catalytic properties for OER and HER. Nevertheless, their conductivity and electrochemical stability at high current density are unsatisfactory, resulting in ineffective water splitting due to high impedance and low stability. Recently, a series of catalysts coating NiFe-based materials on 3D nickel foam were found to be extremely stable under the circumstance of high current density. In this review, we summarized the recent advances of NiFe-based materials on nickel foam for OER and HER, respectively, and further provided the perspectives for their future development.

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P-doped BN nanosheets decorated graphene as the functional interlayer for Li-S batteries Jing Zhang, Wenzhe Ma, Zhenyu Feng, Fangfang Wu, Denghu Wei, Baojuan Xi, Shenglin Xiong 2019, 39(12): 54-60.  摘要 ( 5 )   Lithium-sulfur (Li-S) batteries have attracted much attention due to their ultrahigh theoretical specific capacity. However, serious capacity attenuation caused by shuttle effect still inhibits the performance improvement. Herein, a modified separator consists of the few-layer graphene as a highly conductive network and stable scaffold to support P-doped boron nitride (denoted as BN-P@GO) as the functional interlayer of Li-S batteries. The cell with the interlayer provides an initial discharge capacity as high as 1045.3 mAh g-1, and retains a high reversible capacity of 728.7 mAh g-1 at 1 C after 500 cycles with a capacity decay of 0.061% per cycle. Moreover, the rate capability is also superior to cells with BN@GO or BN-P interlayers, i.e. reversible capcity of 457.9 mAh g-1 even at 3 C. The excellent electrochemical performance is ascribed to the synergistic effect of physical barrier and chemical adsorption for dissolved polysulfides provided by the modified layer. Furhtermore, it also mitigates the polarization and promotes kinetic reactions of the cells. This work provides a concise and effective method for commercialization of lithium-sulfur batteries.

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Directional construction of Cu2S branch arrays for advanced oxygen evolution reaction Shengjue Deng, Yanbin Shen, Dong Xie, Yangfan Lu, Xiaolong Yu, Liang Yang, Xiuli Wang, Xinhui Xia, Jiangping Tu 2019, 39(12): 61-67.  摘要 ( 4 )   Metal sulphide electrocatalyst is considered as one of the most promising low-cost candidates for oxygen evolution reaction (OER). In this work, we report a novel free-standing Cu2S branch array via a facile TiO2-induced electrodeposition-sulfurization method. Interestingly, cross-linked Cu2S nanoflake branch is strongly anchored on the TiO2 backbone forming high-quality Cu2S/TiO2/Cu2S core-branch arrays. The branch formation mechanism is also proposed. As compared to the pure Cu2S nanowire arrays, the asprepared Cu2S/TiO2/Cu2S core-branch arrays show much better alkaline OER performance with lower overpotential (284 mV at 10 mA cm-2) and smaller Tafel slope (72 dec-1) as well as enhanced longterm durability mainly due to larger exposed area and more active electrocatalytic sites. Our work provides a new way for construction of advanced metal sulphide electrocatalysts for electrochemical energy conversion.

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Revalorization of CO2 for methanol production via ZnO promoted carbon nanofibers based Cu-ZrO2 catalytic hydrogenation Israf Ud Din, Maizatul S. Shaharun, A. Naeem, S Tasleem, Pervaiz Ahmad 2019, 39(12): 68-76.  摘要 ( 7 )   A series of novel carbon nanofibers (CNFs) based Cu-ZrO2 catalysts were synthesized by deposition precipitation method. To investigate the influence of promoter, catalysts were loaded with 1, 2, 3 and 4 wt% ZnO and characterized by ICP-OES, HRTEM, BET, N2O chemisorption, TPR, XPS and CO2-TPD techniques. The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst. Copper surface area (SCu) and dispersion (DCu) were slightly decreased by incorporation of ZnO promoter. Nevertheless, SCu and DCu were remarkably decreased when ZnO content was exceeded beyond 3 wt%. The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃, respectively. The promotion of CuZrO2/CNFs catalyst with 3 wt% of ZnO enhanced methanol synthesis rate from 32 to 45 g kg-1 h-1. Notably, with the ZnO promotion the selectivity to methanol was enhanced to 92% compared to 78% of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion. In addition, the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.

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Fe-N-C catalysts for PEMFC: Progress towards the commercial application under DOE reference Lina Wang, Xin Wan, Shuangyu Liu, Li Xu, Jianglan Shui 2019, 39(12): 77-87.  摘要 ( 12 )   Proton exchange membrane fuel cells (PEMFC) have attracted much attention because of their high energy conversion efficiency, high power density and zero emission of pollutants. However, the high cost of the cathode platinum group metal (PGM) catalysts creates a barrier for the large-scale application of PEMFC. Tremendous efforts have been devoted to the development of low-cost PGM-free catalysts, especially the Fe-N-C catalysts, to replace the expensive PGM catalysts. However, the characterization methods and evaluation standards of the catalysts varies, which is not conducive to the comparison of PGM-free catalysts. U.S. Department of energy (DOE) is the only authority that specifies the testing standards and activity targets for PGM-free catalysts. In this review, the major breakthroughs of Fe-N-C catalysts are outlined with the reference of DOE standards and targets. The preparation and characteristics of these highly active Fe-N-C catalysts are briefly introduced. Moreover, the efforts on improving the mass transfer and the durability issue of Fe-N-C fuel cell are discussed. Finally, the prospective directions concerning the comprehensive evaluation of the Fe-N-C catalysts are proposed.

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Multifunctional binder designs for lithium-sulfur batteries Qi Qi, Xiaohui Lv, Wei Lv, Quan-Hong Yang 2019, 39(12): 88-100.  摘要 ( 7 )   Lithium-sulfur (Li-S) batteries are promising next-generation high energy density batteries but their practical application is hindered by several key problems, such as the intermediate polysulfide shuttling and the electrode degradation caused by the sulfur volume changes. Binder acts as one of the most essential components to build the electrodes of Li-S batteries, playing vital roles in improving the performance and maintaining the integrity of the cathode structure during cycling, especially those with high sulfur loadings. To date, tremendous efforts have been devoted to improving the properties of binders, in terms of the viscosity, elasticity, stability, toughness and conductivity, by optimizing the composition and structure of polymer binders. Moreover, the binder modification endows them strong polysulfide trapping ability to suppress the shuttling and decreases the swelling to maintain the porous structure of cathode. In this review, we summarize the recent progress on the binders for Li-S batteries and discuss the various routes, including the binder combination use, functionalization, in-situ polymerization and ion cross-linking, etc., to enhance their performance in stabilizing the cathode, building the high sulfur loading electrode and improving the cyclic stability. At last, the design principles and the problems in further applications are also highlighted.

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Fe3C-N-doped carbon modified separator for high performance lithium-sulfur batteries Hongyu Pan, Zhong Tan, Haihui Zhou, Lanlan Jiang, Zhongyuan Huang, Qiaoxia Feng, Qiang Zhou, Shuai Ma, Yafei Kuang 2019, 39(12): 101-108.  摘要 ( 0 )   A new Fe3C-N-doped reduced graphene oxide (Fe3C-N-rGO) prepared by a facile method is used as a separator for high performance lithium-sulfur (Li-S) batteries. The Fe3C-N-rGO is coated on the surface of commercial polypropylene separator (Celgard 2400) close to the sulfur cathode. The special nanotubes are in-situ catalyzed by Fe3C nanoparticles. They could entrap lithium polysulfides (LiPSs) to restrain the shuttle effect and reduce the loss of active material. The battery with the modified separator and sulfur cathode shows an excellent cycle performance. It has a high rate performance, 580.5 mAh/g at the high current rate of 4 C relative to 1075 mAh/g at 0.1 C. It also has an initial discharge capacity of 774.8 mAh/g measured at 0.5 C and remains 721.8 mAh/g after 100 cycles with a high capacity retention of 93.2%. The outstanding performances are notable in recently reports with modified separator.

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Biomass pyrolysis: A review of the process development and challenges from initial researches up to the commercialisation stage Xun Hu, Mortaza Gholizadeh 2019, 39(12): 109-143.  摘要 ( 94 )   Lignocellulosic biomass can be convert to a condensable liquid named bio-oil, a solid product named as char and a mixture of gaseous products comprising CO2, CO, H2, CH4, etc. In recent years, much effort has been made on the investigation of conversion of biomass through pyrolysis. However, commercialisation of the biomass pyrolysis technology is still challenging due to various issues such as the deleterious properties of bio-oil including the low heating value and the high instability at elevated temperatures. To overcome such issues, many processes, reactors and catalysts have been developed for pyrolysis and catalytic pyrolysis of biomass. A state to the art of pyrolysis or catalytic pyrolysis of biomass need to be summarised to have an overall evaluation of the technologies, in order to provide a useful reference for the further development of pyrolysis technology. This study reviews the various pyrolysis process, especially focus on the effects of essential parameters, the process design, the reactors and the catalysts on the pyrolysis process. In addition, progress in commercialisation of pyrolysis technology was also reviewed and the remaining issues in the process of commercialisation were discussed.

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Oxygen vacancy enhancing mechanism of nitrogen reduction reaction property in Ru/TiO2 Shan Cheng, Yi-Jing Gao, Yi-Long Yan, Xu Gao, Shao-Hua Zhang, Gui-Lin Zhuang, Sheng-Wei Deng, Zhong-Zhe Wei, Xing Zhong, Jian-Guo Wang 2019, 39(12): 144-151.  摘要 ( 12 )   To search the new effective nitrogen reduction reaction (NRR) electrocatalyst is very important for the ammonia-based industry. Herein, we reported the design of a novel NRR electrocatalyst with Ru NPs loaded on oxygen-vacancy TiO2 (Ru/TiO2-Vo). Structural characterizations revealed that oxygen vacancy was loaded in the matrix of Ru/TiO2-Vo. Electrocatalytic results indicated that Ru/TiO2-Vo showed good NRR performance (2.11 μg h-1 cm-2). Contrast tests showed that NRR property of Ru/TiO2-Vo was much better than those of Ru/TiO2(B) (0.53 μg h-1 cm-2) and Ru/P25 (0.42 μg h-1 cm-2). Furthermore, density functional theory calculation results indicated catalytic mechanism of NRR and rate-determining step (*N2 + 1/2H2 → *N+*NH) was the potential-determining step with the overpotential requirement of 0.21 V. A combination of electronic structure analysis and catalytic measurement shed light on the synergistic effect of Ru and oxygen vacancy on the NRR performance.

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Defective ZnS nanoparticles anchored in situ on N-doped carbon as a superior oxygen reduction reaction catalyst Libing Hu, Zengxi Wei, Feng Yu, Huifang Yuan, Mincong Liu, Gang Wang, Banghua Peng, Bin Dai, Jianmin Ma 2019, 39(12): 152-159.  摘要 ( 3 )   Defect engineering has been used to develop low-cost and effective catalysts to boost oxygen reduction reactions. However, the development of catalysts that use metal cation vacancies as the active sites for oxygen reduction reaction is lacking. In this study, ZnS nanoparticles on N-doped carbon serve as an oxygen reduction reaction catalyst. These catalysts were prepared via a one-step method at 900℃. Amazingly, the high-resolution transmission electron microscope image revealed obvious defects in the ZnS nanoparticles. These facilitated the catalyst synthesis, and the product displayed good electrocatalytic performance for the oxygen reduction reaction in an alkaline medium, including a lower onset potential, lower mid-wave potential, four electron transfer process, and better durability compared with 20 wt% Pt/C. More importantly, the density functional theory results indicated that using the Zn vacancies in the prepared catalyst as active sites required a lower reaction energy to produce OOH* from *OO toward oxygen reduction reaction. Therefore, the proposed catalyst with Zn vacancies can be used as a potential electrocatalyst and may be substitutes for Pt-based catalysts in fuel cells, given the novel catalyst's resulting performance.

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Theoretical investigation of lithium ions' nucleation performance on metal-doped Cu surfaces Yanchen Fan, Tianshuai Wang, Dominik Legut, Qianfan Zhang 2019, 39(12): 160-169.  摘要 ( 22 )   Lithium metal batteries (LMBs) of an ultrahigh theoretical energy density have attracted lots of attentions for a wide range of practical applications. However, there are still numerous challenges in LMBs system, such as poor cycling performance, complicated interfacial reactions, low Coulombic efficiency, and uncontrollable lithium dendrites. Understanding Li+ ions' nucleation mechanism is essential to tackle the uncontrolled growth of lithium dendrites. However, the nucleation behavior of Li+ ions is interfered by the structural complexities of existing substrates during the reduplicative plating/stripping process and the rational mechanism of uniform nucleation of Li+ ions has not been clearly understood from the theoretical point of view. In our work, first-principles theoretical calculations are carried out to investigate the Li+ ions nucleation performance on metal-doped Cu surfaces (MDCSs) and the key descriptors that determines the properties of various MDCSs are systematically summarized. It is found that the introduction of heterogeneous doping Ag and Zn atoms will induce a gradient adsorption energy on MDCSs, and such gradient deposition sites can reduce the diffusion barriers and accelerate the diffusion rates of Li+ ions dynamically. By maneuvering the Li+ ions nucleation on MDCSs, a dendrite-free lithium metal anode can be achieved without the use of porous matrixes and complex synthesis process, which can be attributed to suppress the uncontrollable lithium dendrites for realizing the high-efficiency LMBs.

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The role of interstitial species upon the ammonia synthesis activity of ternary Fe-Mo-C(N) and Ni-Mo-C(N) phases Angela Daisley, Justin S. J. Hargreaves 2019, 39(12): 170-175.  摘要 ( 9 )   Fe3Mo3C has been prepared and its activity for ammonia synthesis was evaluated. As had been observed previously for Co3Mo3C, it was found to be inactive at 400℃. At 500℃ activity developed and this can be related to the substitution of lattice carbon by nitrogen. Application of a simple topotactic route to prepare Ni2Mo3C from Ni2Mo3N proved unsuccessful, with the resultant carbonitride formed under optimal synthesis conditions being active for ammonia synthesis at 400℃.

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A multi-layered Ti3C2/Li2S composite as cathode material for advanced lithium-sulfur batteries Xin Liang, Jufeng Yun, Kun Xu, Hongfa Xiang, Yong Wang, Yi Sun, Yan Yu 2019, 39(12): 176-181.  摘要 ( 0 )   Lithium-sulfur (Li-S) batteries with lithium sulfide (Li2S) as cathode have attracted great attention recently, because of high specific capacity (1166 mA h g-1) of Li2S and potential safety of using Li metal-free anode. Li2S cathode has lower volume expansion and higher thermal stability than the traditional sulfur cathode. However, the problems of "shuttle effect" and poor electrical conductivity of the cathode material still need to be overcome. In this work, multi-layered Ti3C2/Li2S (ML-Ti3C2/Li2S) composite has been prepared and applied as a cathode in advanced Li-S batteries. The unique multi-layer sheet structure of Ti3C2 provides space for the storage of Li2S, and its good conductivity greatly enhances the usage ratio of Li2S and improves the conductivity of the whole Li2S cathode. Compared with commonly used graphene, ML-Ti3C2 can trap polysulfides effectively by chemical adsorption and also activate the reaction of Li2S to polysulfides by forming Ti-S bond. As a result, during the cycling of the batteries with ML-Ti3C2/Li2S cathodes, the activation voltage barrier of the first cycle has decreased to 2.8 V, and the "shuttle effect" has been suppressed effectively. The cycling and rate performances of the ML-Ti3C2/Li2S cathodes have been significantly improved compared to that of graphene/Li2S cathodes. They maintain a capacity of 450 mA h g-1 at 0.2 C after 100 cycles, and deliver attractive rate performances of 750, 630, 540, 470 and 360 mA h g-1 at 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C, respectively.

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Facile synthesis of V-doped CoP nanoparticles as bifunctional electrocatalyst for efficient water splitting Jun-Feng Qin, Jia-Hui Lin, Tian-Shu Chen, Da-Peng Liu, Jing-Yi Xie, Bao-Yu Guo, Lei Wang, Yong-Ming Chai, Bin Dong 2019, 39(12): 182-187.  摘要 ( 15 )   Adjusting the intrinsic activity and conductivity of electrocatalysts may be a crucial way for excellent performance for water splitting. Herein, the rational design of vanadium element doped cobalt phosphide (V-doped CoP) nanoparticles has been investigated through a facile gaseous phosphorization using cobalt vanadium oxide or hydroxide (Co-V hydr(oxy)oxide) as precursor. The physical characterization shows that the homogeneous dispersion of V element on V-doped CoP nanoparticles have obtained, which may imply the enhanced electrocatalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The electrochemical measurements of the prepared V-doped CoP in alkaline electrolyte demonstrate the superior electrocatalytic activity for both HER (overpotential of 235 mV@10 mA cm-2) and OER (overpotential of 340 mV@10 mA cm-2). Further, V-doped CoP nanoparticles used as anode and cathode simultaneously in a cell require only 370 mV to achieve a current density of 10 mA cm-2. The outstanding electrocatalytic activity may be ascribed to the improved conductivity and intrinsic activity owing to phosphating and the doping of V element. In addition, the long-term stability of V-doped CoP has been obtained. Therefore, metal doping into transition metal-based phosphides may be a promising strategy for the remarkable bifunctional electrocatalyst for water splitting.

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Kinetic roles of vibrational excitation in RF plasma assisted methane pyrolysis Jintao Sun, Qi Chen 2019, 39(12): 188-197.  摘要 ( 20 )   A combined experimental and simulational work was carried out in this paper to investigate the kinetic effects of non-equilibrium excitation by direct electron impact on low temperature pyrolysis of CH4 in a RF dielectric barrier discharge. Special attention was placed on the vibrational chemistry of CH4 and some other important products including H2, C2H2, C2H4, C2H6 and C3H8 largely produced in CH4/He discharge under an intermediate reduced electric field ranging 51-80 Td. A detailed kinetic mechanism incorporating a set of electron impact reactions, electron-ion recombination reactions, negative ions attachment reactions, charge exchange reactions, reactions involving vibrationally excited molecules and the relaxation process of vibrationally excited species was assembled and experimentally validated. The modeling results showed a reasonable agreement with the experimentally measured results in terms of CH4 conversion and products production including C2 hydrocarbons and hydrogen. A linear increasing trend of methane conversion with increasing plasma power input was discovered, which suggested a strong dependence of molecular excitation on energy input. Both the CH4/He mole ratio and the reactor temperature play significant roles in CH4 conversion and major products production. The experimental results showed that the selectivity of value-added products C2H4 and H2 keeps essentially unchanged with increasing energy input, mostly because the contribution CH4 ionization and He excitation effectively compete with vibrational excitation and dissociation of CH4 molecule with the E/N value increasing. The calculated results showed that the typical relaxation time of vibrational states is comparable to the gas-kinetics time in a CH4/He discharge mixture, thus the vibrationally excited molecules can significantly accelerate chemical reactions through an effective decrease of activation energy. The path flux analysis revealed that the vibrationally excited molecules CH4(v) and H2(v) enhanced chain propagation reactions, such as CH4(v)+H→CH3+H2, CH4(v)+CH→C2H4+H, and H2(v)+C→CH+H, further stimulating the production of active radicals and final products. Specifically, H2(v)+C→CH+H was responsible for 7.9% of CH radical formation and CH4(v)+CH→C2H4+H accounted for 31.4% of total C2H4 production. This kinetic study provides new sights in demonstrating the contribution of vibrationally excited molecules in RF plasma assisted methane pyrolysis.

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Coke-resistant Au-Ni/MgAl2O4 catalyst for direct methanation of syngas Fen Wang, Jing-Cai Zhang, Wei-Zhen Li, Bing-Hui Chen 2019, 39(12): 198-207.  摘要 ( 1 )   Carbon deposition is one of the major issues for catalytic methanation, especially when using high CO content syngas (such as H2/CO=1) due to the inevitable Boudouard reaction. Here we report the significant enhancement on the coke-resistance of Ni/MgAl2O4 catalyst during methanation by modifying with Au. The coke-resistant property was increased with Au addition while the catalytic activity decreased with excess Au. High and stable syngas conversions can be obtained over Au-Ni/MgAl2O4 catalyst at 450-500℃. With comprehensive characterizations by using BET, H2 chemisorption, H2-TPR, XPS, XRD, STEM, EDS, TEM, TG/DTA, Raman and TPH, we found that Au and Ni formed bimetallic nanoparticles of ～10 nm with electron donation from Ni to Au. The deposited carbon on the spent Au-Ni/MgAl2O4 is very similar to that on the spent Ni/MgAl2O4 in the nature and in the gasification behaviour but is significantly less. These results suggest that the enhanced coke-resistance of Au-Ni/MgAl2O4 is presumably due to the suppression on CO disproportionation by modifying Ni with Au.

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Chlorination strategy on polymer donors toward efficient solar conversions Pengjie Chao, Nicolas Johner, Xiaowei Zhong, Hong Meng, Feng He 2019, 39(12): 208-216.  摘要 ( 20 )   Bulk heterojunction (BHJ) polymer solar cells (PSCs) are promising candidates for next-generation solar cells. Benefitting from the persistent efforts in material design and synthesis, systematic device engineering and fundamental understanding of the device physics, the power conversion efficiency (PCE) of single PSC has been pushed to surpass 15%, and that of the tandem PSCs is over 17%. Recently, chlorination has drawn much interest and the chlorinated PSCs have been frequently reported in donor-acceptor (D-A) type conjugated polymers. This review summarizes the recent progress of the chlorinated strategy for highly efficient photovoltaic applications. We firstly discuss the chlorination on the acceptor units in D-A type donor polymers, emphasizing the 4 widely used acceptor units with their improved PCE. secondly, the chlorination on the donor units will be discussed, mainly focusing on the chlorination of benzo[1,2-b:4,b']dithiophene (BDT) unit and 2,2'-bithiophene unit. Remarkably, the PCE of the chlorinated BDT-based device has been improved to over 14%. Overall, this review discusses the structure-property correlations of these chlorinated polymers in photovoltaic study, which could further provide guidance on the chlorinated strategy and the molecular design for high-performance photovoltaic devices.

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Prospects and challenges of graphene based fuel cells Muhammad Zahir Iqbal, Assad-Ur Rehman, Saman Siddique 2019, 39(12): 217-234.  摘要 ( 14 )   Novel characteristics of graphene have captured great attention of researchers for energy technology applications. Incorporation of graphene related hybrid and composite materials have demonstrated high performance and durability for fuel cell energy conversion devices. This article overviews graphene based materials for fuel cell technology applications such as electrodes additives, bipolar plates and proton conducting electrolyte membrane. The graphene dispersion over electrodes has revealed enhanced exposure of electrochemically active surface area for improved electro-catalytic activity towards fuel oxidation and oxidant reduction reactions. The issue of device stack durability and degraded performance due to corrosion of bipolar plates is discussed by incorporating graphene based materials. In proton exchange membrane devices, graphene as an electrolyte has shown an excellent performance towards high ionic conductivity and power density. The graphene incorporation in fuel cell devices has exhibited commendable performance and has bright future for commercial applications.

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Insight into the interaction between Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode and BF4--introducing electrolyte at 4.5 V high voltage Guangyuan Lan, Hebing Zhou, Lidan Xing, Jiawei Chen, Zifei Li, Rude Guo, Yanxia Che, Weishan Li 2019, 39(12): 235-243.  摘要 ( 2 )   Owing to the high specific capacity and high voltage, Ni-rich (LiNi0.8Co0.1Mn0.1O2, LNCM811) cathode has been considered as one of the most promising candidate cathode materials for next generation lithium ion batteries, whereas severe capacity fading greatly hinders its practical application. Notably, the compatibility of Ni-rich materials with LiBF4-containing electrolyte has not yet been realized. Herein, 1 M LiPF6-based electrolyte with introducing 2 M LiBF4 is proposed to dramatically improve the cyclic stability of high voltage LNCM811/Li half-cell. Addition of high concentrated LiBF4 improves the moisture stability of electrolyte, which hinders the generation of harmful by-product HF, resulting in improved interfacial stability of LNCM811. Lithium plating/stripping reaction of Li/Li symmetric cell confirms that the enhanced cyclic stability is ascribed to the improved interfacial stability of LNCM811 instead of lithium electrode. Morphology and composition characterization results reveal that LiBF4 participates in the CEI film-forming reaction, resulting in suppressed oxidation of electrolyte and interfacial structural destruction of LNCM811.

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Kinetic studies of reversible hydrogen storage over sodium phenoxide-cyclohexanolate pair in aqueous solution Yang Yu, Qijun Pei, Teng He, Ping Chen 2019, 39(12): 244-248.  摘要 ( 16 )   With reduced dehydrogenation enthalpy change and reduced dehydrogenation temperature compared with its phenol-cyclohexanol pair, sodium phenoxide-cyclohexanolate pair developed recently is promising for large-scale energy storage and long-distance hydrogen transportation. In the present work, we investigate the kinetic behavior of the pair in the hydrogenation and dehydrogenation in water over three commercial catalysts. It is shown that 5% Ru/Al2O3 and 5% Pt/C perform well in the hydrogenation and dehydrogenation, respectively. Kinetic analyses show that the hydrogenation of sodium phenoxide is of first-order with respect to H2 pressure and zero-order to the concentration of sodium phenoxide in the presence of Ru/Al2O3 catalyst.>99% conversion of cyclohexanol and>99% selectivity to phenoxide can be achieved in the dehydrogenation catalyzed by Pt/C catalyst and in the presence of NaOH at 100℃, where cyclohexanone was observed as an intermediate. According to the kinetic analysis, the hydrogenation of sodium phenoxide may undergo the hydrolysis and hydrogenation pathway. For the dehydrogenation, an intermediate, i.e., cyclohexanone, was detected and two possible pathways are proposed accordingly.

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Te0.045S0.955PAN composite with high average discharge voltage for Li-S battery Ke Wang, Yuepeng Guan, Zhaoqing Jin, Weikun Wang, Anbang Wang 2019, 39(12): 249-255.  摘要 ( 5 )   As a sulfur-containing cathode material, sulfide polyacrylonitrile (SPAN) is expected to be used for longlife lithium-sulfur battery because there is no shuttle effect occurred in its charge process. However, its specific capacity and discharge potential need to be further improved to satisfy the urgent demands for high-performance batteries. In this paper, Te0.045S0.955PAN composite was synthesized by co-heating TexS1-x and PAN, and the superior electrochemical performance to that of SPAN was obtained because of doping Te with high conductivity. The as-prepared Te0.045S0.955PAN composite possessed the specific capacity of 675 mAh g-1 after 100 cycles at the current density of 0.1 A g-1 with high capacity retention of 96.6% compared to the second cycle. Especially, during cycling, Te0.045S0.955PAN showed average discharge voltages of 1.88-1.91 V, which were higher than 1.85-1.88 V for SPAN at the same current density. Thus doping Te provides a new strategy for increasing the energy density of SPAN.

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Ultra-deep adsorptive removal of thiophenic sulfur compounds from FCC gasoline over the specific active sites of CeHY zeolite Yun Zu, Chang Zhang, Yucai Qin, Xiaotong Zhang, Li Zhang, Honghai Liu, Xionghou Gao, Lijuan Song 2019, 39(12): 256-267.  摘要 ( 7 )   Adsorption desulfurization performance of NaY, HY and CeHY zeolites is evaluated in a miniature fixedbed flow by model gasoline containing with thiophene, tetrahydrothiophene, 2-methylthiophene, benzothiophene or mixed sulfur compounds. The structural properties of adsorbents are characterized by XRD, N2-adsorption and XPS techniques. Adsorption desulfurization mechanisms of these sulfur compounds over the specific active sites of adsorbents as a major focus of this work, have been systematically investigated by using in situ FT-IR spectroscopy with single and double probing molecules. Desulfurization experimental results show that the CeHY adsorbent exhibits superior adsorption sulfur capacity at breakthrough point of zero sulfur for ultra-deep removal of each thiophenic sulfur compound, especially in the capture of aromatic 2-methylthiophene (about ca. 28.6 mgS/gadsorbent). The results of in situ FT-IR with single probing molecule demonstrate an important finding that high oligomerization ability of thiophene or 2-methylthiophene on the CeHY can promote the breakthrough adsorption sulfur capacity, mainly resulting from the synergy between Brønsted acid sites and Ce(III) hydroxylated species active sites located in the supercages of CeHY. Meanwhile, the result of in situ FT-IR with double probing molecules further reveals the essence of oligomerization reactions of thiophene and 2-methylthiophene molecules on those specific active sites. By contrast, the oligomerization reaction of benzothiophene molecules on the active sites of CeHY cannot occur due to the restriction of cavity size of supercages, but they can be adsorbed on the Brønsted acid sites via protonation, and on Ce(III) hydroxylated species and extra-framework aluminum hydroxyls species via direct "S-M" bonding interaction. As to the tetrahydrothiophene, adsorption mechanism is similar to that of benzothiophene, except in the absence of protonation. The paper can provide a new design idea of specific adsorption active sites in excellent desulfurization adsorbents for elevating higher quality of FCC gasoline in the future.

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Effect of doped Ni-Bi-B alloy on hydrogen generation performance of Al-InCl3 Jun Chen, F. Xu, L. Sun, Kexiang Zhang, Yongpeng Xia, Xiaolei Guo, Huanzhi Zhang, Fang Yu, Erhu Yan, Hongliang Peng, Pengru Huang, Shujun Qiu, Cuili Xiang, Yujie Sun 2019, 39(12): 268-274.  摘要 ( 16 )   In this work, Ni-Bi-B alloy has been synthesized via chemical synthesis method. A new kind of Al-InCl3-(Ni-Bi-B) composite has been prepared by high energy mechanical ball grinding Al powder with additives. Results show that the doped Ni-Bi-B alloy can significantly improve the hydrogen generation performance of Al-InCl3 and the catalytic activity is enhanced with the increasing content of Bi in Ni-Bi-B alloy. Under optimal conditions, the hydrogen generation yield and conversion yield of Al-InCl3-(Ni-Bi-B) reached 1196.8 mL g-1 and 100.0% at room temperature, respectively. Mechanism study shows five kinds of active sites, such as the fresh surface/defect of Al particle, Al-AlCl3, Al-In, Al-Bi/B and Al-Ni/B produced during the ball milling process. Their synergistic effect enhances the hydrogen generation performance of AlInCl3-(Ni-Bi-B) remarkably. In general, the proposed Al-InCl3-(Ni-Bi-B) composite is possible to serve as hydrogen generation material for fuel cells.

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Corrigendum to “TiO2 supported cobalt-manganese nano catalysts for light olefins production from syngas”[Journal of Energy Chemistry 22(4) (2013) 645-652] Mostafa Feyzi, Asadollah Hassankhani 2019, 39(12): 275-275.  摘要 ( 0 )

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Journal of Energy Chemistry in its 6th anniversary Yang Gao, Lijuan Zhang 2019, 39(12): 276-277.  摘要 ( 29 )