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2019, Vol. 30, No. 3　Online: 2019-03-15


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CO₂ High-quality Sb₂Se₃ nanowires: Fast, green microwave synthesis and energy storage (Pages 27-33)

Metal chalcogenides semiconductors are of technological importance due to their typical narrow band gap and size-dependent properties, thus have held promise in the applications of thermoelectrics, photovoltaics and energy storage. In this paper, a facile solvent-mediated process is demonstrated whereby Sb₂Se₃ nanowires and Se microrods can be achieved by merely varying the volume ratio of ethylene glycol and H₂O free from expensive chemical and additional surfactant. The achieved uniform Sb₂Se₃ nanowire is single crystalline along [001] growth direction with a diameter of 100 nm and a length of tens of micrometers. Meanwhile Sb₂Se₃ nanowires can deliver high reversible capacity and superior rate capability when evaluated as an anode for lithium-ion battery. This easy solvent-mediated microwave approach exhibits its universe and importance towards the wide application of metal chalcogenide for future low-cost, large-scale energy systems.

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TiO2 hierarchical pores/nanorod arrays composite flm as photoanode for quantum dot-sensitized solar cells Xing Du, Lei Zhao, Xuan He, Hui Chen, Weixin Li, Wei Fang 2019, 28(3): 1-7.  DOI: 10.1016/j.jechem.2018.01.005 摘要 ( 429 )   Power conversion efficiency (PCE) of quantum dot-sensitized solar cells (QDSSCs) was boosted in a TiO2 composite film (TCSF) with delicate design in structure where TiO2 hierarchical porous film (THPF) situated on the top of TiO2 nanorod arrays film (TNAF). In this case, TNAF could supply efficient scattering centers for high light harvesting and direct electrical pathways for fast electron transfer while the THPF could offer porous channels for loading high quantity of previously synthetized quantum dots (QDs) and facilitate the penetration of electrolyte. Meanwhile, in this specific configuration, the presence of anatase- rutile heterojunction at the interface could help the rutile TNAF layer to efficiently collect photo-injected electrons from the anatase THPF layer thus suppressing the recombination of electrons and holes in electrolyte. The results showed that the PCE of QDSSC based on the TNAF photoanode was about 1.4-fold higher (η=3.05%, Jsc=15.86 mA cm-2, Voc=0.602 V, FF=0.319) than that of device based on pure THPF (η=2.20%, Jsc=13.82 mA cm-2, Voc=0.572 V, FF=0.278).

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Theoretical investigation of loading Ni clusters on the α-Ga2O3 surfaces for photocatalytic hydrogen evolution Jiaxin Zhang, Yidan Wang, Hao Dong, Xin Zhou 2019, 28(3): 8-18.  DOI: 10.1016/j.jechem.2018.03.007 摘要 ( 408 )   In the semiconductor-based photocatalysts for overall water splitting, loading proper cocatalysts play a crucial role in enhancing the photocatalytic activity. In this work, we have chosen Nin/α-Ga2O3 as a model and provided detailed density functional theory calculations to investigate the function of cocatalysts in hydrogen evolution reaction (HER). We have studied the formation and stability of Nin (n=1-4) cluster on two stable surfaces of α-Ga2O3 (001) and (012). In a Nin/α-Ga2O3 system, as the Ni 3d states well overlap with O and Ga states, the excited electrons transferred from Ga to Ni may participate in HER. We theoretically predict that introduction of Nin cluster on (012) surface can elevate the Fermi level toward the conduction band, which is favorable for the occurrence of HER. Electrochemical computations are used to explore the mechanism of HER. It is found that, in most of Nin/α-Ga2O3 systems, the active sites of HER are on Nin clusters. Loading Nin clusters not only importantly reduces the Gibbs free energy of HER but also improves the reaction activity of surface O and Ga sites in HER. Our calculations reasonably explain the experimental observation on significant enhancement of activity for generating hydrogen after loading nickel oxide cocatalysts.

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Choice for graphene as conductive additive for cathode of lithium-ion batteries Ying Shi, Lei Wen, Songfeng Pei, Minjie Wu, Feng Li 2019, 28(3): 19-26.  DOI: 10.1016/j.jechem.2018.03.009 摘要 ( 445 )   Graphene is a promising conductive additive for the lithium-ion batteries (LIBs) and shows great potential especially with its fast development of the large scale fabrication technology. This work has explored the influence of the incorporation of graphenes prepared by three typical methods on the electrochemical performance of the LiCoO2-based cathode focusing on the choice for the effective graphene as conductive additive for the cathode of LIBs. Through the comparison of the intrinsic characteristics of graphenes and the electrochemical performance of electrodes with graphene, it is found that graphene with low disorder degree and large size is not suitable for LiCoO2 cathodes as conductive additive. Conversely, the graphene with oxygen functional groups, relatively low surface area and proper size displays much better electrochemical performance when it is used as conductive additive. This work also demonstrates the transmission mechanism for different graphenes as conductive additives in the LiCoO2 materials, and further reveals that the conductivity of graphene is not the only factor as conductive additives, surface chemistry and sheet size of the graphene are also essential factors which greatly influence the electrochemical performance of electrode. In addition, when combined with Super P, only 1% graphene is enough to construct an efficient conductive network in the electrode. This study also gives a new sight on the practical application of graphene as conductive additive for high performance LIBs.

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Fast, green microwave-assisted synthesis of single crystalline Sb2Se3 nanowires towards promising lithium storage Wen Luo, Jean-Jacques Gaumet, Pierre Magri, Sébastien Diliberto, Feng Li, Pascal Franchetti, Jaafar Ghanbaja, Liqiang Mai 2019, 28(3): 27-33.  DOI: 10.1016/j.jechem.2018.03.013 摘要 ( 395 )   In this work, a fast (0.5 h), green microwave-assisted synthesis of single crystalline Sb2Se3 nanowires was developed. For the first time we demonstrated a facile solvent-mediated process, whereby intriguing nanostructures including antimony selenide (Sb2Se3) nanowires and selenium (Se) microrods can be achieved by merely varying the volume ratio of ethylene glycol (EG) and H2O free from expensive chemical and additional surfactant. The achieved uniform Sb2Se3 nanowire is single crystalline along[001] growth direction with a diameter of 100 nm and a length up to tens of micrometers. When evaluated as an anode of lithium-ion battery, Sb2Se3 nanowire can deliver a high reversible capacity of 650.2 mAh g-1 at 100 mA g-1 and a capacity retention of 63.8% after long-term 1000 cycles at 1000 mA g-1, as well as superior rate capability (389.5 mAh g-1 at 2000 mA g-1). This easy solvent-mediated microwave synthesis approach exhibits its great universe and importance towards the fabrication of high-performance metal chalcogenide electrode materials for future low-cost, large-scale energy storage systems.

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Selective Hydrogenolysis of 5-Hydroxymethylfurfural to 2, 5-Dimethylfuran over Co3O4 catalyst by Controlled reduction Dan Li, Qiying Liu, Changhui Zhu, Haiyong Wang, Chunhua Cui, Chenguang Wang, Longlong Ma 2019, 28(3): 34-41.  DOI: 10.1016/j.jechem.2018.03.008 摘要 ( 394 )   2,5-dimethyfuran (DMF), which is produced from 5-hydroxymethyfurfural (HMF) by hydrodeoxygenation (HDO), is a high quality fuel due to the high heating value, the high octane number and the suitable boiling point. Selective hydrogenation of HMF into liquid fuel DMF has been widely researched. In this paper, Co3O4 catalyst was prepared by co-precipitation and was reduced at different temperatures to form Co-CoOx catalysts. The characterization of catalysts was tested by XRD, TEM, XPS, TPR, BET and NH3-TPD. Co-CoOx possessed a high amount of Co metal and CoOx acidic sites, wherein Co worked as the active hydrogenation sites and CoOx acted as the acid promoter to facilitate the selective HDO of HMF to DMF. The synergistic effect of Co-CoOx is the key for HDO of HMF, obtaining 83.3% of DMF yield at 170℃, 12 h and the reduction temperature of 400℃. This method not only saves the catalyst cost, but also promotes the utilization of biomass energy.

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The effect of oxidation of ethane to oxygenates on Pt- and Zn-containing LTA zeolites with tunable selectivity Baoyu Liu, Su Cheun Oh, Huiyong Chen, Dongxia Liu 2019, 28(3): 42-48.  DOI: 10.1016/j.jechem.2018.04.001 摘要 ( 403 )   Platinum and zinc containing LTA zeolite catalysts with tunable meso/microporosity were prepared by using ligand-metal precursors under hydrothermal condition. These materials were employed for oxidation of ethane to oxygenates using hydrogen peroxides as oxidant under mild reaction condition. The results showed that platinum and zinc loaded LTA zeolites were effective for the partial oxidation of ethane with hydrogen peroxide giving the desired C2 oxygenates. Moreover, the C1 oxygenates were also obtained through subsequent C-C bond scission pathways. The over oxidation of ethanol/methanol to acetic acid/formic acid could be inhibited through the introduction of mesoporosity in LTA zeolites. Our findings for oxidation of ethane suggested that the selectivity to the oxidation products such as alcohols and acids could be tailored by tuning the metal species within the LTA zeolites and porosity of catalysts, indicating that a balance between the meso/microporosity and metal species in LTA zeolites can be realized for desirable catalysis by one-pot synthesis of zeolites. In addition, the selectivity to oxygenates can also be tuned by control of the reaction conditions, i.e. concentration of hydrogen peroxide or reaction time.

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Well-aligned NiPt alloy counter electrodes for high-effciency dye-sensitized solar cell applications Zhibin Pang, Yuanyuan Zhao, Yanyan Duan, Jialong Duan, Qunwei Tang, Liangmin Yu 2019, 28(3): 49-56.  DOI: 10.1016/j.jechem.2018.03.016 摘要 ( 400 )   Development of cost-effective and robust counter electrodes (CEs) is a persistent objective for highefficiency dye-sensitized solar cells (DSSCs). To achieve this goal, we present here the hydrothermal synthesis of well-aligned NiPt alloy CEs, which is templated by ZnO nanowires and nanosheets. The preliminary results demonstrate that NiPt alloy electrodes are featured by increased charge-transfer processes and electrocatalytic activity in comparison with expensive Pt CE, yielding power conversion efficiencies of 8.29% and 7.41% in corresponding DSSCs with NiPt nanowire and nanosheet alloy CEs, respectively. Additionally, the NiPt alloy CEs also display extraordinary dissolution-resistant ability when suffering longterm utilization in liquid-junction DSSCs.

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Nanosheet-structured K-Co-MoS2 catalyst for the higher alcohol synthesis from syngas:Synthesis and activation Huan Li, Wei Zhang, Yinyin Wang, Meiling Shui, Song Sun, Jun Bao, Chen Gao 2019, 28(3): 57-62.  DOI: 10.1016/j.jechem.2018.03.019 摘要 ( 383 )   The nanosheets structured K-Co-MoS2 catalyst was prepared through a one-step hydrothermal synthesis combined with the wetness impregnation. The fresh catalyst has a high dispersion of Co-Mo-S active phase and no Co9S8 is found. The pure H2 activated catalyst shows a higher intrinsic activity, especially the C2+OH selectivity for the higher alcohol synthesis compared to the one activated by 5% H2/N2 atmosphere. The reason is attributed to that the pure H2 activation more effectively suppresses the formation of Co9S8 and stabilizes the Co-Mo-S active phase during the reaction due to the formation of SH species.

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Facile fabrication of hierarchical porous Co3O4 nanoarrays as a free-standing cathode for lithium-oxygen batteries Yanbiao Ren, Shuang Zhao, Honglei Li, Shichao Zhang, Jian Liu, Yao Xiao 2019, 28(3): 63-70.  DOI: 10.1016/j.jechem.2018.03.012 摘要 ( 442 )   Two shapes of Co3O4 nanoarrays (i.e., nanosheets, nanowires) with different densities of exposed catalytic active sites were synthesized through a facile hydrothermal method on Ni foam substrates and tested as the binder/carbon free and free-standing cathodes for Li-O2 batteries. Particularly, the single crystalline feature of Co3O4 nanosheets with a predominant high reactivity {112} exposed crystal plane and hierarchical porous nanostructure displayed better catalytic performance for both oxygen reduction reaction (during discharge process) and oxygen evolution reaction (during charge process). Li-O2 battery with Co3O4 nanosheets cathode exhibited a higher discharge specific capacity (965 mAh g-1), lower discharge/charge over-potential and better cycling performance over 63 cycles at 100 mA g-1 with the specific capacity limited at 300 mAh g-1. The superior catalytic performance of Co3O4 nanosheets cathode is ascribed to the enlarging specific area and increasing the exposed Co3+ catalytic active sites within predominant {112} crystal plane which plays the key role in determining the adsorption energy for the reactants, enabling high round-trip efficiency and cyclic life.

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Highly effcient and selective photocatalytic dehydrogenation of benzyl alcohol for simultaneous hydrogen and benzaldehyde production over Ni-decorated Zn0.5Cd0.5S solid solution Lei Zhang, Daochuan Jiang, Rana Muhammad Irfan, Shan Tang, Xin Chen, Pingwu Du 2019, 28(3): 71-77.  DOI: 10.1016/j.jechem.2018.03.014 摘要 ( 417 )   Photocatalytic conversion of solar energy into hydrogen and high value-added fine chemicals has attracted increasing attention. Herein, we demonstrate an efficient photocatalytic system for simultaneous hydrogen evolution and benzaldehyde production by dehydrogenation of benzyl alcohol over Nidecorated Zn0.5Cd0.5S solid solution under visible light. The photocatalytic system shows an excellent hydrogen production rate of 666.3 μmol h-1 with high stability. The optimal apparent quantum yield of 52.5% is obtained at 420 nm. This noble-metal-free photocatalytic system displays much higher activity than pure Zn0.5Cd0.5S and Pt-loaded Zn0.5Cd0.5S solid solution. Further studies reveal that the metallic Ni nanocrystals play an important role in accelerating the separation of photogenerated charge carriers and the subsequent cleavage of α-C-H bond during dehydrogenation of benzyl alcohol.

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Dissolution and recrystallization of perovskite induced by N-methyl-2-pyrrolidone in a closed steam annealing method Lili Zhi, Yanqing Li, Xiaobing Cao, Yahui Li, Xian Cui, Lijie Ci, Jinquan Wei 2019, 28(3): 78-83.  DOI: 10.1016/j.jechem.2018.03.017 摘要 ( 442 )   High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone (NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH3NH3PbI3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.

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Naphthalene-modulated microporous carbon layers of LiFePO4 improve the high-rate electrochemical performance Taotao Huo, Ning Nie, Yuanyuan Liu, Jinli Zhang, Feng Yu, Wei Li 2019, 28(3): 84-89.  DOI: 10.1016/j.jechem.2018.04.002 摘要 ( 387 )   Carbon layers with microporous structures fine-modulated by naphthalene (NAP) were prepared to coat on LiFePO4, aiming to enhance the Li+ diffusion coefficient for Li-ion batteries. Characterized by BET, XRD, TEM, EIS, etc., it is indicated that in the presence of NAP, the carbon-coated LiFePO4/C-NAP composites have the enlarged micropore size of 1.66 nm and the enhanced Li+ diffusion coefficient of 2.83×10-12 cm2 s-1, which is about five times higher than that of LiFePO4/C prepared in the absence of NAP. At a high rate of 20 C, the discharge capacity of the LiFePO4/C-NAP is up to 120.1 mA h g-1 and maintains a good retention rate of 93.2% after 400 cycles. It is suggested that the NAP-modulated carbon coating is a promising route to accelerate the Li-ion diffusion rate and enhance the electrochemical performance for lithium ion batteries.

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Effect of hydrophilic silica nanoparticles on hydrate formation:Insight from the experimental study Ren Wang, Tianle Liu, Fulong Ning, Wenjia Ou, Ling Zhang, Zhen Wang, Li Peng, Jiaxin Sun, Zhichao Liu, Tianshu Li, Huicui Sun, Guosheng Jiang 2019, 28(3): 90-100.  DOI: 10.1016/j.jechem.2018.02.021 摘要 ( 458 )   Invasion of drilling fluid into natural gas hydrate deposits during drilling might damage the reservoir, induce hydrate dissociation and then cause wellbore instability and distortion of the data from well logging. Adding nanoparticles into drilling fluid is an effective method in reducing the invasion of drilling fluid and enhancing borehole stability. However, the addition of nanoparticles might also introduce hydrate formation risk in borehole because they can act as the "seeds" for hydrate nucleation. This paper presents an experimental study of the effect of hydrophilic silica nanoparticle on gas hydrate formation in a dynamic methane/liquid-water system. In the experiment, the ultrapure water with and without 1.0 wt%-6.0 wt% concentrations of silica nanoparticles, grain sizes of 20 and 50 nm, were pressurized by methane gas under varied conditions of temperature and pressure. The induction time, the gas consumption, and the average rate of gas consumption in the system were measured and compared to those in ultrapure water. The results show that a concentration of 4.0 wt% hydrophilic SiO2 particles with a grain size of 50 nm has a relatively strong inhibition effect on hydrate formation when the initial experimental condition is 5.0℃ and 5.0 MPa. Compared to ultrapure water, the hydrophilic nano-SiO2 fluid increases the induction time for hydrate formation by 194% and decreases the amount and average rate of hydrate formation by 10% and 17%, respectively. This inhibition effect may be attributed to the hydrophilicity, amount and aggregation of silica nanoparticle according to the results of water activity and zeta potential measurements. Our work also elucidates hydrophilic, instead of hydrophobic, nanoparticles can be added to the drilling fluid to maintain wellbore stability and to protect the hydrate reservoir from drilling mud damage, because they exhibit certain degree of hydrate inhibition which can reduce the risk of hydrate reformation and aggregation during gas hydrate or deep water drilling if their concentration can be controlled properly.

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High performance n+p-Si/Ti/NiSxOy photocathode for photoelectrochemical hydrogen evolution in alkaline solution Qing Jia, Chunlin Yu, Wei Liu, Guokui Zheng, Chaojun Lei, Lecheng Lei, Xingwang Zhang 2019, 28(3): 101-107.  DOI: 10.1016/j.jechem.2018.04.004 摘要 ( 375 )   Silicon, as a promising semiconductor for fabricating photocathode toward photoelectrochemical hydrogen evolution reaction (PEC-HER), should be improved in light harvesting ability and catalytic kinetics to obtain high PEC performance. Herein, a novel amorphous Nickel Oxysulfide (NiSxOy) film is effectively integrated with a Ti protected n+p-Si micropyramid photocathode by the electrodeposition method. The fabricated n+p-Si/Ti/NiSxOy photocathode exhibits excellent PEC-HER performance with an onset potential of 0.5 V (at J=-0.1 mA/cm2), a photocurrent density of -26 mA/cm2 at 0 V vs. RHE, and long term stability of six hours in alkaline solution (pH ≈ 14). The synergy of unique n+p-Si micropyramid architectures (omnidirectional broadband light harvesting ability), novel amorphous NiSxOy catalyst (high HER electrocatalytic activity and good optical transparency) results in the high performance of n+pSi/Ti/NiSxOy. This work offers a novel strategy for effectively integrating electrocatalysts with semiconductor to design efficient photoelectrode toward PEC water splitting.

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First-principles kinetics study of carbon monoxide promoted Ostwald ripening of Au particles on FeO/Pt(111) Sulei Hu, Runhai Ouyang, Wei-Xue Li 2019, 28(3): 108-113.  DOI: 10.1016/j.jechem.2018.03.023 摘要 ( 420 )   The dynamic and kinetic evolution of supported metal particles in the presence of reactants is decisive in shaping the nature of the catalytic active sites and the deactivation process. Ostwald ripening of FeO/Pt(111) supported Au particles in the presence of carbon monoxide is addressed here by firstprinciples kinetics. It is found that CO stabilizes the ripening monomer (Au atom) by forming favorable Au carbonyls with lower total activation energy, and corresponding phase diagram at wide range of temperature and CO pressures is constructed. Evolution of particle number, dispersion and particle size distribution of supported Au particles are explored. Great influence of CO promotion on ripening kinetics is revealed and explored in details, and mbar range of CO can lower the onset temperature of ripening by a few hundred kelvins. The present work reveals the crucial role of the metal-reactant complexes formed under reaction conditions on ripening of metal catalysts.

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A novel thermomechanically stable LaF3CsH5(PO4)2 composite electrolyte with high proton conductivity at elevated temperatures over 150℃ Jie Xiong, Yunjie Huang, Jing Li, Liying Ma, Guoxiao Xu, Zhao Liu, Weiwei Cai, Hansong Cheng 2019, 28(3): 114-120.  DOI: 10.1016/j.jechem.2018.04.006 摘要 ( 405 )   A facile strategy is introduced to upgrade thermomechanical stability of the cesium pentahydrogen diphosphate (CPD), which is the most efficient inorganic electrolyte among all solid proton conductors, by constructing P-OH…F hydrogen bonds with lanthanum fluoride (LaF3). The optimal combination of the LaF3-CPD composite electrolyte is found to be 1:2 in a molar ratio (LaF3-CPD-2). LaF3-CPD-2 composite maintains robust solid state, even at a temperature up to 200℃, which is 50℃ higher than the melting temperature of CPD. Meanwhile, the considerable proton conductivity of CPD is achieved in the LaF3-CPD-2 composite electrolyte due to the synergistic effect of the P-OH…F hydrogen bonds and the intrinsic proton conductive property of CPD. Last but not least, the LaF3-CPD-2 composite manifests excellent conductivity durability at 150℃ and low humidity condition with sizeable proton conductivity of 0.0262 S cm-1 after 60 h operation, implying that the LaF3-CPD composite could be a promising candidate for intermediate temperature proton conductors.

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Sulfur-encapsulated in heteroatom-doped hierarchical porous carbon derived from goat hair for high performance lithium-sulfur batteries Juan Ren, Yibei Zhou, Huali Wu, Fengyu Xie, Chenggang Xu, Dunmin Lin 2019, 28(3): 121-131.  DOI: 10.1016/j.jechem.2018.01.015 摘要 ( 463 )   Biomass-derived carbon materials have aroused widespread concern as host material of sulfur to enhance electrochemical performances for lithium-sulfur batteries. Herein, goat hair, as a low-cost and eco-friendly precursor, is employed to fabricate cauliflower-like in-situ nitrogen, oxygen and phosphorus tri-doped porous biomass carbon (NOPC) by a facile activation with H3PO4 and carbonization process. The morphology and microstructure of NOPC can be readily tuned by altering pyrolysis temperature. The as-prepared NOPC matrix material carbonized at 600℃ possesses 3D hierarchical porous structure, high specific surface area (535.352 m2 g-1), and appropriate pore size and pore size distribution. Encapsulating sulfur into the NOPC depends on a stem-melting technology as cathode materials of Li-S batteries. Due to the synergistic effect of special physical structure and inherent tri-doping of N, O and P, electrons and ions transfer and utilization of active sulfur in the materials are improved, and the shuttle behaviors of soluble lithium polysulfides are also mitigated. Consequently, the S/NOPC-600 composite exhibits excellent electrochemical performance, giving a high initial discharge capacity of 1185 mA h g-1 at 0.05 C and maintaining a relatively considerable capacity of 489 mA h g-1 at 0.2 C after 300 cycles. Our work shows that a promising candidate for cathode material of Li-S batteries can be synthesized using low-cost and renewable biomass materials by a facile process.

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Characteristics of MOF, MWCNT and graphene containing materials for hydrogen storage:A review Kranthi Kumar Gangu, Suresh Maddil, Saratchandra Babu Mukkamala, Sreekantha B Jonnalagadda 2019, 28(3): 132-144.  DOI: 10.1016/j.jechem.2018.04.012 摘要 ( 455 )   Hydrogen is a generally abundant, safe, clean and environmentally apt alternative fuel, which replenishes the void generated by depleting fossil fuel reserves. The adoption of hydrogen as an energy source has been restricted to low levels due to the complications associated with its viable storage and usage. Existing technologies, such as storage of hydrogen in compressed and liquefied forms are not adequate to meet the broad on-board applications. The gravimetric energy density (120 MJ/kg) of hydrogen is three times higher than that of gasoline products, so solid-state hydrogen storage is advantageous. Metal-organic frameworks (MOFs), multi-walled carbon nanotubes (MWCNTs) and graphene are solid adsorbents majorly employed for efficient H2 storage. The prominent features of MOFs such as permanent porosity, structural rigidity, and surface area are attractive and ideal for hydrogen storage. In addition, nanostructured carbon materials (MWCNTs and graphene) and their composites have demonstrated significant hydrogen storage capacities. Some important parameters for the success of the hydrogen economy include high storage density, adsorption/desorption temperature and cycling time. Cryo-hydrogen storage was achieved in MOFs and their composites with carbon structures, but storage at ambient temperature and acceptable pressures is a major hurdle. This review discusses various strategies and mechanisms in the design of adsorbents explored to improve H2 storage capacities and afford opportunities to develop new sustainable hydrogen technologies to meet energy targets.

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V2O5·nH2O nanosheets and multi-walled carbon nanotube composite as a negative electrode for sodium-ion batteries Ahmed S. Etman, Junliang Sun, Reza Younesi 2019, 28(3): 145-151.  DOI: 10.1016/j.jechem.2018.04.011 摘要 ( 427 )   Two dimensional (2D) transition metal oxides and chalcogenides demonstrate a promising performance in sodium-ion batteries (SIBs) application. In this study, we investigated the use of a composite of freeze dried V2O5·nH2O nanosheets and multi-walled carbon nanotube (MWCNT) as a negative electrode material for SIBs. Cyclic voltammetry (CV) results indicated that a reversible sodium-ion insertion/deinsertion into the composite electrode can be obtained in the potential window of 0.1-2.5 V vs. Na+/Na. The composite electrodes delivered sodium storage capacities of 140 and 45 mAh g-1 under applied current densities of 20 and 100 mA g-1, respectively. The pause test during constant current measurement showed a raise in the open circuit potential (OCP) of about 0.46 V, and a charge capacity loss of ～10%. These values are comparable with those reported for hard carbon electrodes. For comparison, electrodes of freeze dried V2O5·nH2O nanosheets were prepared and tested for SIBs application. The results showed that the MWCNT plays a significant role in the electrochemical performance of the composite material.

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C-C formation mediated by photoinduced electrons from crystallized carbon nitride nanobelts under visible light irradiation Qiaohui Jia, Sufen Zhang, Quan Gu 2019, 28(3): 152-161.  DOI: 10.1016/j.jechem.2018.07.015 摘要 ( 391 )   Crystal structure and crystallinity of carbon nitride support, size and dispersity of active-metal nanoparticles (NPs), and surface engineering of composites have great roles in generation and separation of photogenerated charge carries and photocatalyzed organic reactions for the conversion of solar energy into chemical energy. Herein, we deposited well-dispersed Pd NPs with small size on crystallized carbon nitride (CN-C) to construct a Schottky-type Pd/CN-C hybrid for photocatalyzed Ullmann C-C homocoupling of aryl halides under visible light irradiation at room temperature. Compared to Pd NPs supported g-C3N4 (Pd/g-C3N4), Pd/CN-C exhibits excellent visible light photocatalytic activity for Ullmann C-C coupling of aryl halides due to high crystallinity of CN-C support, high dispersion and smaller size of Pd NPs, and the interfacial heterojunction of Pd/CN-C. Upon visible light irradiation, more photogenerated electrons from CN-C flow across the Schottky junction to metallic Pd and trigger the Ullmann C-C coupling of aryl halides. The photogenerated holes on CN-C surface are captured by a protic solvent (such as EtOH). In the presence of base K2CO3, the solvent undergoes dissociation, dehydrogenation, and finally can be oxidized by captured photogenerated holes. Moreover, Pd/CN-C has general applicability for various substrates and shows excellent stability and reusability for more than nine cycles.

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Ferrierite vs. γ-Al2O3:The superiority of zeolites in terms of water-resistance in vapour-phase dehydration of methanol to dimethyl ether Enrico Catizzone, Massimo Migliori, Antonio Purita, Girolamo Giordano 2019, 28(3): 162-169.  DOI: 10.1016/j.jechem.2018.05.004 摘要 ( 362 )   The catalytic conversion of methanol to dimethyl ether (DME) over a series of home-made FER-type zeolites having different acidities and commercial γ-Al2O3 has been studied with the aim to understand the impact of adding water in the reactant stream on the catalytic behavior on investigated materials. Cofeeding water with methanol, the alcohol conversion was slightly reduced over the investigated zeolites while the catalytic activity of γ-Al2O3, the traditional catalyst of MeOH-to-DME conversion, was strongly inhibited. It was also found that, for the investigated zeolites, both the amount and the initial deposition rate of the coke formed during the reaction were reduced when water was co-fed with methanol while no significant effects on both methanol conversion and DME selectivity were observed under the investigated conditions.