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2019, Vol. 31, No. 4　Online: 2019-04-15


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From pomelo peel to efficient electrocatalyst: A green and costeffective approach (Pages 89-94)
Pt counter electrode (CE) enables dye-sensitized solar cells (DSCs) to achieve high power conversion efficiency, however, the high cost has become a bottleneck limiting the development of DSCs. In this paper, a green and cost-effective approach is presented to utilize biomass (pomelo peel) as precursor for synthesis of porous carbon with multiple active components. The abundant functional hetero-metal atoms doped into carbon framework can play a role of catalytic graphitization, which leads a high conductivity. When serving as CE in DSC, this electrocatalyst yields high power conversion efficiency comparable to that based on Pt-CE, which can be ascribed to the synergistic effect of self-activation and the co-doping of nitrogen, sulphur and phosphorus all together in carbon matrix. The facile approach is believed to be a promising strategy for lowering the cost and advancing the development DSCs.

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Incorporating the magnetic alignment of GO composites into Pebax matrix for gas separation Weifang Zhu, Yun Qin, Zhongming Wang, Jianshu Zhang, Ruili Guo, Xueqin Li 2019, 28(4): 1-10.  DOI: 10.1016/j.jechem.2018.04.013 摘要 ( 349 )   The mixed matrix membranes (MMMs) were developed by incorporating graphite oxide (GO) flakes functionalized with iron oxide (Fe3O4) into Pebax matrix. The Pebax/Fe3O4-GO MMMs were used to separate CO2/CH4 and CO2/N2 gas mixture. The results showed that the MMMs with magnetic alignment presented the better gas separation performance than that of random arrangement of Pebax/Fe3O4-GO mixed matrix membranes. The reason was that the Fe3O4-GO flakes arranged magnetically in the membrane played a multiple role in improving the performance of MMMs. Firstly, under the action of the magnetic field, the magnetic alignment of Fe3O4-GO flakes in Pebax matrix constructed the shorter transfer path for gas molecule, increasing the CO2 permeability. Secondly, the hydroxyl groups in GO flakes and the presence of Fe3O4 have stronger binding force for water, improving the CO2 solubility selectivity. Thirdly, the better interaction between the magnetic alignment of GO composites and polymer matrix, reduced the interface defects. Especially, the optimum gas separation performance was obtained at the Fe3O4-GO flakes content of 3 wt% in Pebax matrix at vertical arrangement with selectivity of 47 and 75 for CO2/CH4 and CO2/N2, respectively, and CO2 permeability of 538 Barrer at 0.2 MPa and room temperature.

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Synthesis of Ti2CTx MXene as electrode materials for symmetric supercapacitor with capable volumetric capacitance Kai Zhu, Yuming Jin, Fei Du, Shuang Gao, Zhongmin Gao, Xing Meng, Gang Chen, Yingjin Wei, Yu Gao 2019, 28(4): 11-18.  DOI: 10.1016/j.jechem.2018.03.010 摘要 ( 329 )   Two-dimensional (2D) metal carbides, MXene, present the promising application for the energy storage system. Among the MXene family, Ti2CTx as the lightest material, shows its unique electrochemical performance. Herein, Ti2CTx is synthesized by selective etching Al layer from the Ti2AlC. With the optimized HF treating condition, Ti2CTx displays high volumetric capacitance and remarkable rate ability. Moreover, the Ti2CTx//Ti2CTx symmetric supercapacitor is designed and assembled, which presents capable capacitance, outstanding rate performance and excellent cycling performance. The remarkable electrochemical performance is attributed to its 2D structure and high electronic conductivity. This work demonstrates the potential application of the Ti2CTx for the supercapacitors and provides a template to design highperformance supercapacitors with 2D electrode materials.

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An ultrathin and continuous Li4Ti5O12 coated carbon nanofiber interlayer for high rate lithium sulfur battery Decheng An, Lu Shen, Danni Lei, Lehong Wang, Heng Ye, Baohua Li, Feiyu Kang, Yan-Bing He 2019, 28(4): 19-26.  DOI: 10.1016/j.jechem.2018.05.002 摘要 ( 367 )   Severe capacity fading and poor high rate performance of lithium sulfur (Li-S) battery caused by "shuttle effect" and low conductivity of sulfur hampers its further developments and applications. Li4Ti5O12 (LTO) possesses high lithium ion conductivity, and it is also can be used as an active adsorbent for polysulfide. Herein, fine LTO particle coated carbon nanofibers (CNF) were prepared and a conductive network both for electron and lithium ion was built, which can greatly promote the electrochemical conversion of polysulfide and improve the rate performance of Li-S batteries. Meanwhile, a quantity of adsorption sites is constructed by defects of the surface of LTO-CNF membrane to effectively immobilize polysulfide. The multifunctional LTO-CNF interlayer could impede the shuttle effect and enhance comprehensive electrochemical performance of Li-S batteries, especially high rate performance. With such LTO-CNF interlayer, the Li-S battery presents a specific capacity of 641.9 mAh/g at 5 C rate. After 400 cycles at 1 C, a capacity of 618.0 mAh/g is retained. This work provides a feasible strategy to achieve high performance of Li-S battery for practical utilization.

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High-performance asymmetric small molecular donor materials based on indenothiophene for solution-processed organic solar cells Hua Tan, Baoqi Wu, Jun Zhang, Qiang Tao, Wenhong Peng, Weiguo Zhu 2019, 28(4): 27-33.  DOI: 10.1016/j.jechem.2018.05.007 摘要 ( 306 )   Two novel asymmetric organic small molecules of IT(2FBT-T3Cz)2 and IT(2FBT-TT3Cz)2 with an indenothiophene (IT) central donor core, fluorinated benzothiadiazole (2FBT) as acceptor and 3-carbazole (Cz) unit as terminal group were designed and synthesized as the donor materials in organic solar cells (OSCs). The thermal, optical absorption, electrochemical property, hole-electron mobility, film morphology were thoroughly studied. Using PC71BM as an electron acceptor, without any additive and thermal annealing (TA) treatment, the IT(2FBT-T3Cz)2-based cells showed a promising power conversion efficiency (PCE) of 5.81% and the IT(2FBT-TT3Cz)2-based cells exhibited a PCE of 4.39%. Our results demonstrate that the IT-based asymmetric small molecules can be developed as a promising class of donor materials for highperformance OSCs.

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Self-assembly of three-dimensional CdS nanosphere/graphene networks for efficient photocatalytic hydrogen evolution Zhijian Wang, Zhi Liu, Jiazang Chen, Hongbin Yang, Jianqiang Luo, Jiajian Gao, Junming Zhang, Cangjie Yang, Suping Jia, Bin Liu 2019, 28(4): 34-38.  DOI: 10.1016/j.jechem.2018.05.006 摘要 ( 301 )   In this work, we report the construction of three-dimensional (3D) CdS nanosphere/graphene networks by a one-step hydrothermal self-assembly route. The 3D graphene networks not only enhance the light scattering, thanks to the interconnected 3D architecture, but also improve the crystallinity of deposited CdS nanospheres, and at the same time provide a direct electron pathway to quickly separate the photogenerated electron-hole pairs from CdS, which thus dramatically improve the photocatalytic activity. The optimized 3D CdS nanosphere/graphene networks with 2 wt% of graphene could produce molecular hydrogen at a rate of 2310 μmol gcatalyst-1 h-1 under visible-light illumination (λ > 400 nm).

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Pretreatment of agricultural residues by supercritical CO2 at 50-80℃ to enhance enzymatic hydrolysis Meng-jiao Zhao, Qin-qin Xu, Guo-min Li, Qiao-zhi Zhang, Dan Zhou, Jian-zhong Yin, Hua-shu Zhan 2019, 28(4): 39-45.  DOI: 10.1016/j.jechem.2018.05.003 摘要 ( 321 )   Various agricultural crop residues including corn stover, corn cob, and sorghum stalk with a moisture content of 75 wt% were subjected to a long pretreatment (12-60 h) with supercritical CO2 (scCO2), at low temperature (50-80℃) and a pressure of 17.5-25.0 MPa. The sugar yields from the enzymatic hydrolysis (EH) of the pretreated samples were as much as three-to fourfold greater than those afforded by the raw materials. However, when pretreatment was conducted within a short time (e.g. 0.5 h), as previously reported in the literature, only a slight increase in the EH sugar yields was observed. The proposed scCO2 pretreatment mechanism demonstrated the role of moisture in the system. Wetting, softening, and swelling were observed to mainly affect the lignocellulose when a suitable amount of water was added. Finally, the samples were analysed by X-ray diffraction and scanning electron microscopy, before and after pretreatment, to investigate the changes in the microscopic structure of the biomass.

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Gas-phase electrocatalytic conversion of CO2 to chemicals on sputtered Cu and Cu-C catalysts electrodes N. Gutiérrez-Guerra, J. A. González, J. C. Serrano-Ruiz, E. López-Fernández, J. L. Valverde, A. de Lucas-Consuegra 2019, 28(4): 46-53.  DOI: 10.1016/j.jechem.2018.05.005 摘要 ( 298 )   A novel gas-phase electrocatalytic cell containing a low-temperature proton exchange membrane (PEM) was developed to electrochemically convert CO2 into organic compounds. Two different Cu-based cathode catalysts (Cu and Cu-C) were prepared by physical vapor deposition method (sputtering) and subsequently employed for the gas-phase electroreduction of CO2 at different temperatures (70-90℃). The prepared electrodes Cu and Cu-C were characterized by X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and scanning electron microscopy (SEM). As revealed, Cu is partially oxidized on the surface of the samples and the Cu and Cu-C cathodic catalysts were comprised of a porous, continuous, and homogeneous film with nanocrystalline Cu with a grain size of 16 and 8 nm, respectively. The influence of the applied current and temperature on the electro-catalytic activity and selectivity of these materials was investigated. Among the two investigated electrodes, the pure Cu catalyst film showed the highest CO2 specific electrocatalytic reduction rates and higher selectivity to methanol formation compared to the Cu-C electrode, which was attributed to the higher particle size of the former and lower CuO/Cu ratio. The obtained results show potential interest for the possible use of electrical renewable energy for the transformation of CO2 into valuable products using low metal loading Cu based electrodes (0.5 mg Cu cm-2) prepared by sputtering.

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Review and prospect of NiCo2O4-based composite materials for supercapacitor electrodes Yanmei Li, Xiao Han, Tingfeng Yi, Yanbing He, Xifei Li 2019, 28(4): 54-78.  DOI: 10.1016/j.jechem.2018.05.010 摘要 ( 326 )   Supercapacitors known as typical electrochemical capacitors have been considered as one of the most promising candidates of energy storage systems owing to their advantages such as high-power density, long life span and lower production cost. The electrode materials play a crucial role on properties of supercapacitors. Hence, many researches have been focused on the development of novel electrode materials for high-performance supercapacitors. NiCo2O4 as supercapacitor electrode material has drawn more and more attentions in recent years due to its outstanding advantages, such as high theoretical capacity, low cost, natural abundance and easy of synthesis. However, the NiCo2O4 always suffer from severe capacity deterioration because of the low electrical conductivity and small surface area. Hence, it is necessary to systematically and comprehensively summarize the progress in understanding and modifying NiCo2O4-based materials from various aspects. In this review, the structure and synthesis method of NiCo2O4-based materials are discussed in detail. And then, the major goal of this review is to highlight new progress in using proposed strategies to improve the cycling stability and rate capacity of NiCo2O4-based materials, including synthesis, control of special morphologies and design of composite materials. Finally, an insight into the future research and development of NiCo2O4-based materials for supercapacitors is prospected.

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Electrochemical engineering approach of high performance solid-state flexible supercapacitor device based on chemically synthesized VS2 nanoregime structure Bidhan Pandit, Lakshmana Kumar Bommineedi, Babasaheb R. Sankapal 2019, 28(4): 79-88.  DOI: 10.1016/j.jechem.2018.05.011 摘要 ( 283 )   Portable and furnished electronics appliances demand power efficient energy storage devices where electrochemical supercapacitors gain much more attention. In this concern, a simple, low-cost and industry scalable successive ionic layer adsorption and reaction (SILAR) approach has been adopted to deposit nanostructured VS2 onto flexible and light-weight stainless steel (SS) substrate towards supercapacitor application. The nanocrystalline nature with hexagonal crystal structure has been confirmed for VS2 through structural analysis. The VS2 electrode exhibits a maximum specific capacitance of 349 F g-1 with a super stable behavior in three-electrode liquid-state configuration. Fabricated flexible symmetric solid-state supercapacitor (FSSC) device using gel electrolyte yields specific power of 1.5 kW kg-1 (specific energy of 25.9 Wh kg-1) with a widen voltage window of 1.6 V. A red LED has been glown for 30 s using the system consisted of two devices in series combination. Furthermore, the system glows a combination of 21 red LEDs network with acronym ‘VNIT’, demonstrating commercial exposure. The attribution of device demonstration even under mechanical stress holds great promise towards advanced flexible electronics application.

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Multiple active components synergistically driven heteroatom-doped porous carbon as high-performance counter electrode in dye-sensitized solar cells Hongyu Jing, Danyang Wu, Suxia Liang, Xuedan Song, Yonglin An, Ce Hao, Yantao Shi 2019, 28(4): 89-94.  DOI: 10.1016/j.jechem.2018.03.011 摘要 ( 332 )   A facile template-free in situ self-activation approach for the multiple active components synergistically driven porous carbon was presented via a feasible annealing process. The biomass-derived carbon without additional activation reagents was fabricated using K-rich pomelo peel (PP) as the carbon source, which possesses a high electric conductivity where abundant functional hetero-metal atoms are doped into the carbon framework that playing the role of catalytic graphitization. The K+ that exists within the biomass can induce self-activation during pyrolysis apart from the activating gases during the pyrolysis process. The resulting electrocatalyst of PP-850 (PP was pyrolyzed at 850℃ in an N2 atmosphere) with abundant heteroatoms possesses a higher power conversion efficiency (PCE) of 7.81% as the counter electrode (CE) of dye-sensitized solar cells (DSCs) compared with the CEs calcinated at other temperatures and a similar PCE with Pt counterpart (8.24%) based on the liquid I3-/I-electrolyte. The better electrocatalytic performance is attributed to the synergistic effect between self-activation and the co-doping of nitrogen, sulfur and phosphorus all together in a carbon matrix. Due to the feasibility of large-scale production, rich heteroatom doping, the PP-derived carbon, which simplifies the procedure and decreases the cost, has a potential application for an alternative electrocatalyst for high-performance photovoltaic devices.

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Activated carbon fibers with manganese dioxide coating for flexible fiber supercapacitors with high capacitive performance Huifang Li, Jiachen Liang, Huan Li, Xiaoyu Zheng, Ying Tao, Zheng-Hong Huang, Quan-Hong Yang 2019, 28(4): 95-100.  DOI: 10.1016/j.jechem.2018.05.008 摘要 ( 256 )   Fiber supercapacitor (FSC) is a promising power source for wearable/stretchable electronics and high capacitive performance of FSCs is highly desirable for practice flexible applications. Here, we report a composite of manganese dioxide (MnO2) and activated carbon fibers (ACFs) with high MnO2 mass loading and microporous structure (abbreviated as MnO2@ACF), which is used as a fiber electrode to produce a FSC with a high capacitive performance and a good flexibility. The MnO2@ACF composite electrode in FSCs delivers an ultrahigh specific capacitance of 410 mF/cm2 at 0.1 mA/cm2, corresponding to a high energy density of 36 μWh/cm2 and high power density of 726 μW/cm2. Such high capacitive performance and simple fabrication method indicates that the MnO2@ACF composite is a very promising electrode material for flexible fiber supercapacitors.

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Precise carbon structure control by salt template for high performance sodium-ion storage Dong Qiu, Tengfei Cao, Jun Zhang, Si-Wei Zhang, Dequn Zheng, Haoliang Wu, Wei Lv, Feiyu Kang, Quan-Hong Yang 2019, 28(4): 101-106.  DOI: 10.1016/j.jechem.2018.05.014 摘要 ( 369 )   Carbon materials are considered to be one of the most promising anode materials for sodium-ion batteries (SIBs), but the well-ordered graphitic structure limits the intercalation of sodium ions. Besides, the sluggish intercalation kinetics of sodium ions impedes the rate performance. Thus, the precise structure control of carbon materials is important to improve the battery performance. Herein, a 3D porous hard-soft composite carbon (3DHSC) was prepared using the NaCl as the template and phenolic resin and pitch as carbon precursors. The NaCl template restrains the growth of the graphite crystallite during the carbonization process, resulting in small graphitic domains with expanded interlayer spacing which is favorable for the sodium storage. Moreover, the NaCl templates help to create abundant mesopores and macropores for fast sodium ion diffusion. The porous structure and the graphite crystalline structure can be precisely controlled by simply adjusting the mass ratio of NaCl, and thus, the suitable structure can be prepared to reach high capacity and rate performance while keeping a relatively high Coulombic efficiency. Typically, a high reversible capacity (215 mA h g-1 at 0.05 A g-1), an excellent rate capability (97 mA h g-1 at 5 A g-1), and a high initial Coulombic efficiency (60%) are achieved.

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Comparative evaluation for catalytic gasification of petroleum coke and asphaltene in subcritical and supercritical water Rachita Rana, Sonil Nanda, Aimee Maclennan, Yongfeng Hu, Janusz A. Kozinski, Ajay K. Dalai 2019, 28(4): 107-118.  DOI: 10.1016/j.jechem.2018.05.012 摘要 ( 337 )   Subcritical and supercritical water gasification of petroleum coke and asphaltene was performed at variable temperatures (350-650℃), feed concentrations (15-30 wt%) and reaction times (15-60 min). Nickel-impregnated activated carbon (Ni/AC) was synthesized as a catalyst for enhancing syngas yields at optimal gasification conditions (650℃, 15 wt% and 60 min). Structural chemistry of precursors and chars developed at different gasification temperatures was studied using physicochemical and synchrotronbased approaches such as carbon-hydrogen-nitrogen-sulfur (CHNS) analysis, thermogravimetric and differential thermogravimetric analysis (TGA/DTA), scanning electron microscopy (SEM), Fourier-Transform Infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Asphaltene testified to be a better precursor for catalytic hydrothermal gasification leading to 11.97 mmol/g of total gas yield compared to petroleum coke (8.04 mmol/g). In particular, supercritical water gasification using 5 wt% Ni/AC at 650℃ with 15 wt% feed concentration for 60 min resulted in 4.17 and 2.98 mmol/g of H2 from asphaltene and petroleum coke, respectively. Under the same conditions, the respective CH4 yields from catalytic gasification of asphaltene and petroleum coke were 2.54 and 1.07 mmol/g. Nonetheless, asphaltene also seemed to an attractive feedstock for the production of highly aromatic chars through hydrothermal gasification.

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Electrochemical process of sulfur in carbon materials from electrode thickness to interlayer Xiaonan Tang, Zhenhua Sun, Huicong Yang, Haitao Fang, Fei Wei, Hui-Ming Cheng, Shuping Zhuo, Feng Li 2019, 28(4): 119-124.  DOI: 10.1016/j.jechem.2018.06.001 摘要 ( 332 )   Lots of efforts have been done on different porous carbon materials as cathode for Lithium-sulfur (Li-S) battery. However, seldom researches have been done on the relationship between cathode thickness and electrochemical performance. Our work investigates the relation between electrochemical performance and cathode thickness with typical porous carbon materials. We explain the phenomenon that only a modest cathode thickness can have the most adequate electrochemical reaction trend through the aspect of thermodynamics (chemical potential) so that the best electrochemical performance can be obtained. Besides, interlayer can remit the shuttle effect but hinder the lithium ion diffusion process simultaneously. And we verify the effect of interlayer thickness on the shuttle effect and lithium ion diffusion process.

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Rational synthesis of CaCo2O4 nanoplate as an earth-abundant electrocatalyst for oxygen evolution reaction Xiao Lin, Jing Zhou, Dehua Zheng, Chengzhi Guan, Guoping Xiao, Ning Chen, Qing Liu, Hongliang Bao, Jian-Qiang Wang 2019, 28(4): 125-131.  DOI: 10.1016/j.jechem.2018.05.015 摘要 ( 284 )   To accelerate the kinetics of oxygen evolution reaction (OER) regarding the energy conversion and storage approaches, the discovery of desirable cost-effective and highly efficient electrocatalysts is of prime importance. This study demonstrates a layered CaCo2O4 with a two-dimensional nanoplate structure, which possesses electrocatalytic activity for OER. The OER activity was achieved on CaCo2O4 with a Tafel slope of 71 mV dec-1 and a current density of 10 mA cm-2 at an overpotential of 371 mV, which was more active than the similar structure LiCoO2 catalyst. Combined with X-ray absorption fine structure and density functional theory calculations, the enhanced OER activity and stability are mainly attributed to the unique electronic structure derived from the interaction of Ca and Co, and improved electrical conductivity. CaCo2O4 can be developed as a highly active and earth-abundant catalyst for OER in energy conversion and storage technologies.

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A new Tin-based O3-Na0.9[Ni0.45-x/2MnxSn0.55-x/2]O2 as sodium-ion battery cathode Xiaohui Rong, Xingguo Qi, Yaxiang Lu, Yuesheng Wang, Yunming Li, Liwei Jiang, Kai Yang, Fei Gao, Xuejie Huang, Liquan Chen, Yong-Sheng Hu 2019, 28(4): 132-137.  DOI: 10.1016/j.jechem.2018.05.019 摘要 ( 395 )   Recently, sodium-ion batteries (SIBs), regarded as promising supplements for lithium-ion batteries (LIBs), especially in the large-scale energy storage field, are attracting more and more attention. However, the limited suitable cathode materials hinder the wide commercialization of SIBs. Given this aspect, in this work, a new layered oxide with 4d metal Tin was synthesized and investigated as cathode material for SIBs. Two optimized sodium-deficient O3-Na0.9Ni0.45Sn0.55O2 and O3-Na0.9Ni0.4Mn0.1Sn0.5O2 were selected for comprehensive investigation, both of which exhibited high operating voltage of around 3.45 V with smooth charge/discharge curves. In comparison, O3-Na0.9Ni0.4Mn0.1Sn0.5O2 shows a higher reversible capacity (65 mA h/g, 0.1 C), better rate capability and cycling stability than that of O3-Na0.9Ni0.45Sn0.55O2 (50 mA h/g, 0.1 C), indicating that a small amount of Mn-substitution can improve the electrochemical performance. This work presents a new possibility of discovering potential cathode candidates by exploring the Tin-based layered oxides.

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Room temperature pretreatment of pubescens by AlCl3 aqueous solution Yue Wang, Xiaoyan Lv, Jindong Li, Qiuxing Li, Changwei Hu 2019, 28(4): 138-147.  DOI: 10.1016/j.jechem.2018.06.005 摘要 ( 326 )   Room temperature (about 16℃) pretreatment of pubescens by AlCl3 aqueous solution with different concentrations was studied. In the presence of 20 wt% AlCl3 for pretreatment within 24 h, the degradation of hemicellulose reached 19.5 wt% without obvious degradation of cellulose and lignin (2.7 wt% and 2.4 wt%, respectively). The extracted hemicellulose from pubescens could be divided into two parts, i.e., small molecular weight products (saccharides and carboxylic acid, which occupy approximately 28.2%) and oligomers (approximately 71.8%). Low concentration of AlCl3 (<10 wt%) slightly promoted the formation of oligomers with molecular weight in the range of 200-1000 Da, while high concentration of AlCl3 (10-20 wt%) promoted the formation of oligomers in the molecular weight range above 20,000 Da. The conversion of hemicellulose with acceptable selectivity resulted in the cleavage of bond between hemicellulose and lignin yielding three classical Lignin-Carbohydrate complexes.

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A highly active and stable Pd/B-doped carbon catalyst for the hydrogenation of 4-carboxybenzaldehyde Kai Tie, Xiulian Pan, Tie Yu, Pan Li, Limin He, Xinhe Bao 2019, 28(4): 154-158.  DOI: 10.1016/j.jechem.2018.05.021 摘要 ( 295 )   Boron had been introduced into the structure of carbon material (BC), which was used as the support of Pd catalyst for hydrogenation of 4-carboxybenzaldehyde (4-CBA). The physical properties and chemical composition of the support and corresponding catalyst were characterized by N2 adsorption-desorption, Raman spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), element analysis (EA), high-resolution transmission electron microscopy (HRTEM), CO-pulse chemisorption and X-ray photoelectron spectroscopy (XPS). The results demonstrate that Pd/BC catalyst exhibits a superior activity and good stability due to the more uniform dispersion of Pd nanoparticles, the presence of mesoporous structure and the enhanced interaction between Pd nanoparticles and the support, compared to carbon and N-doped carbon supported Pd catalysts (Pd/C and Pd/NC, respectively).

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High specific surface area porous graphene grids carbon as anode materials for sodium ion batteries Hao Zhang, Huinan Guo, Aiyang Li, Xiaoya Chang, Song Liu, Dun Liu, Yijing Wang, Fang Zhang, Huatang Yuan 2019, 28(4): 159-166.  DOI: 10.1016/j.jechem.2018.06.002 摘要 ( 266 )   Although great accomplishments of functional material synthesis have been achieved in sodium ion batteries (SIBs) recently, there are still numerous challenges and problems in preparing carbon-based materials with porous architectures and enough lattice distance for Na+ insertion. Herein we report a templated strategy to synthesize 3D porous graphene girds (PGGs) consisting of several stacking graphene structure with ultrahigh surface area and hierarchical connected structure by employing Ag nanoparticles (NPs). The Ag NPs will regenerate for decreasing the experimental cost, also in line with principles of green chemistry and environmentally friendly strategy. The PGGs obtain advanced specific capacity of 160 mA h g-1 at current density of 50 mA h g-1. Moreover, 112 mA h g-1 capacity can be gained at 1 A h g-1 during 1000 cycles. Due to their porous architecture, ultrahigh surface area and low amorphous graphited structure, PGGs electrode showed the excellent electrochemical performance in high rate capability.

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Mesoporous NiCo2O4 nanoneedles@MnO2 nanoparticles grown on nickel foam for electrode used in high-performance supercapacitors Yanmei Li, Jingjing Pan, Jinzhu Wu, Tingfeng Yi, Ying Xie 2019, 28(4): 167-177.  DOI: 10.1016/j.jechem.2018.06.009 摘要 ( 295 )   Mesoporous NiCo2O4@MnO2 nanoneedle arrays as electrode materials for supercapacitor grown on a conductive nickel foam were prepared by a facile hydrothermal route. The interconnected mesoporous structure of the NiCo2O4 nanoneedle arrays provides a large specific surface area for charge storage. The electrochemically active MnO2 nanoparticles covered on the surface of NiCo2O4 nanoneedle result in a favorable synergistic storage effect because of charge redistribution at the NiCo2O4|MnO2 interface, which reduces the interfacial polarization and facilitates ion diffusion. The initial specific capacitance of NiCo2O4@MnO2 (S2) is 1001 F g-1 at current density of 15 A g-1. The capacity retention of S2 is about 87.4% after 4000 cycles, and the specific capacitance of S2 electrode only decreases from 1001 F g-1 to 736 F g-1 even after 10,000 cycles. The first-principles calculations show that a chemical bonding between the NiCo2O4 and MnO2 is not only helpful for stabilizing the composites but also leads to a charge redistribution at the interface, which may lead to a smaller interfacial polarization and thus beneficial for the interfacial capacity. The excellent electrochemical performance of NiCo2O4@MnO2 composites (S2) can be ascribed to the high surface area, unique architecture, MnO2 nanoparticle modification, reduced charge transfer resistance and stable interface between NiCo2O4 and MnO2. The simple material synthesis and architectural design strategy provides new insights in opportunities to exhibit promising potential for practical application in energy storage.