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2016, Vol. 25, No. 1　Online: 2016-01-15


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Ultrafine nitrogen doped TiO₂ nanoparticles: excellent performance for water splitting

This paper reports the facile synthesis, characterization and solar-light driven photocatalytic water-splitting of ultrafine nitrogen-doped TiO₂ photocatalyst (N-TiO₂). The N-TiO₂ nanoparticles were fabricated via a PVP-assisted solvothermal method and characterized in terms of their structure, morphological, optical and photocatalytic water-splitting properties. The dual function of PVP acted as both nitrogen source and stabilizer showed potential usage in the synthesis process of solar-light driven semiconductors. The excellent performance in water-splitting was attributed to the ultrafine particle size, hydrophilic groups on the surface and the successful doping of nitrogen.

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Well-dispersed ultrafine nitrogen-doped TiO2 with polyvinylpyrrolidone (PVP) acted as N-source and stabilizer for water splitting Tianyu Liu, Wei Chen, Xiaoheng Liu, Junwu Zhu, Lude Lu 2016, 25(1): 1-9.  DOI: 10.1016/j.jechem.2015.11.009 摘要 ( 5498 )   In this paper, ultrafine nitrogen-doped TiO2 photocatalystwith enhanced photocatalyticwater-splitting properties was successfully fabricated via a solvothermal method. Herein, polyvinylpyrrolidone (PVP) was used as both nitrogen source and stabilizer. The enhancement in water-splitting process can be attributed to the doping of element nitrogen, which could supply an intermediate energy level and promote the separation of photo-excited holes and electrons. Moreover, this paper provides a new application of high-molecular polymer to synthesize solar-driven water-splitting photocatalysts.

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Biomass gasification technology: The state of the art overview Antonio Molino, Simeone Chianese, Dino Musmarra 2016, 25(1): 10-25.  DOI: 10.1016/j.jechem.2015.11.005 摘要 ( 6476 )   In the last decades the interest in the biomass gasification process has increased due to the growing attention to the use of sustainable energy. Biomass is a renewable energy source and represents a valid alternative to fossil fuels. Gasification is the thermochemical conversion of an organic material into a valuable gaseous product, called syngas, and a solid product, called char. The biomass gasification represents an efficient process for the production of power and heat and the production of hydrogen and second-generation biofuels. This paper deals with the state of the art biomass gasification technologies, evaluating advantages and disadvantages, the potential use of the syngas and the application of the biomass gasification. Syngas cleaning though fundamental to evaluate any gasification technology is not included in this paper since; in the authors' opinion, a dedicated review is necessary.

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Low-cost, green synthesis of highly porous carbons derived from lotus root shell as superior performance electrode materials in supercapacitor Xin Wang, Mengjiao Wang, Xuemei Zhang, Hejun Li, Xiaohui Guo 2016, 25(1): 26-34.  DOI: 10.1016/j.jechem.2015.10.012 摘要 ( 5130 )   Facile production of high quality activated carbons from biomass materials has greatly triggered much attention presently. In this paper, a series of interconnected porous carbon materials from lotus root shells biomass are prepared via simple pyrolysis and followed by a KOH activation process. The prepared carbons exhibit high specific surface areas of up to 2961 m2/g and large pore volume~1.47 cm3/g. In addition, the resultant porous carbons served as electrode materials in supercapacitor exhibit high specific capacitance and outstanding recycling stability and high energy density. In particular, their specific capacitance retention was almost 100% after 10500 cycles at a current density of 2 A/g. Remarkabely, the impact of the tailored specific surface areas of various carbon samples on their capacitive performances is systematically investigated. Generally, it was believed that the highly-developed porosity features (including surface areas and pore volume and pore size-distributions), together with the good conductivity of activated carbon species, play a key role in effectively improving the storage energy performances of the porous carbon electrode materials in supercapacitor.

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Biomass-derived activated carbon materials with plentiful heteroatoms for high-performance electrochemical capacitor electrodes Xiangyang Zhou, Hongcheng Li, Juan Yang 2016, 25(1): 35-40.  DOI: 10.1016/j.jechem.2015.11.008 摘要 ( 7035 )   Activated carbons for electrochemical capacitor electrodes are prepared from soyabean using chemical activation with KOH. The pore size is easily controllable by changing the mass ratio between KOH and carbonized product. The as-prepared materials possess a large specific surface area, unique structure, well- developed hierarchical porosity and plentiful heteroatoms (mainly O and N). Thus resulted in its high specific capacitance, good rate capacity and cycling stability. Moreover, attributing to worldwide availability, renewable nature and low-cost, activated carbon prepared from soyabean has a good potential in energy conversion and storage devices.

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Influence of TiO2 on the electrochemical performance of pasted type β-nickel hydroxide electrode in alkaline electrolyte B. Shruthi, B. J. Madhu, V. Bheema Raju 2016, 25(1): 41-48.  DOI: 10.1016/j.jechem.2015.11.006 摘要 ( 5222 )   Nickel hydroxide was used as the positive electrode material in rechargeable alkaline batteries, which plays a significant role in the field of electric energy storage devices. β-nickel hydroxide (β-Ni(OH)2) was prepared from nickel sulphate solution using potassium hydroxide as a precipitating agent. Pure β-phase of nickel hydroxide was confirmed from XRD and FT-IR studies. The effects of TiO2 additive on the β-Ni(OH)2 electrode performance are examined. The structure and property of the TiO2 added β-Ni(OH)2 were characterized by XRD, TG-DTA and SEM analysis. A pasted-type electrode is prepared using nickel hydroxide powder as the main active material on a nickel sheet as a current collector. Cyclic voltammetry and electrochemical impedance spectroscopy studies were performed to evaluate the electrochemical performance of the β-Ni(OH)2 and TiO2 added β-Ni(OH)2 electrodes in 6 M KOH electrolyte. Anodic (Epa) and cathodic (Epc) peak potentials are found to decrease after the addition of TiO2 into β-Ni(OH)2 electrode material. Further, addition of TiO2 is found to enhance the reversibility of the electrode reaction and also increase the separation of the oxidation current peak of the active material from the oxygen evolution current. Compared with pure β-Ni(OH)2 electrode, TiO2 added β-Ni(OH)2 electrode is found to exhibit higher proton diffusion coefficient (D) and lower charge transfer resistance. These findings suggest that the TiO2 added β-Ni(OH)2 electrode possess improved electrochemical properties and thus can be recognized as a promising candidate for the battery electrode applications.

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Three-dimensional paper-like graphene framework with highly orientated laminar structure as binder-free supercapacitor electrode Yidan Gao, Yaoyao Zhang, Yong Zhang, Lijing Xie, Xiaoming Li, Fangyuan Su, Xianxian Wei, Zhiwei Xu, Chengmeng Chen, Rong Cai 2016, 25(1): 49-54.  DOI: 10.1016/j.jechem.2015.11.011 摘要 ( 5531 )   A free-standing paper-like three-dimensional graphene framework (3DGF) with orientated laminar structure and interconnected macropores, was obtained by the hard template-directed ordered assembly. As the sacrificial templates, polystyrene (PS) latex spheres were assembled with graphene oxide (GO) to build up a sandwich type composite film, followed by heat removal of which with a simultaneous reduction of GO. The 3DGF exhibited high specific surface area of 402.5 m2/g, controllable pores and mechanical flexibility, which was employed as the binder-free supercapacitor electrode and shows high specific gravimetric capacitance of 95 F/g at 0.5 A/g, with enhanced rate capability in 3 electrode KOH system.

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Enhanced photo-catalytic activity of the composite of TiO2 and conjugated derivative of polyvinyl alcohol immobilized on cordierite under visible light irradiation Jin Zhang, Haigang Yang, Long Jiang, Yi Dan 2016, 25(1): 55-61.  DOI: 10.1016/j.jechem.2015.10.010 摘要 ( 4784 )   A novel visible light active photo-catalyst named CHC/C-PVA/TiO2, the composite of titanium dioxide (TiO2) with conjugated derivative of polyvinyl alcohol (C-PVA) loaded on a cordierite honeycomb ceramic (CHC) substrate, was fabricated by combining the synthesis of TiO2 sol, preparation of C-PVA via thermally treating polyvinyl alcohol, and immobilization of TiO2 sol and C-PVA on CHC. By detecting the change of UV-vis absorption spectra of the model organic pollutant (methyl orange (MO)) in the presence of the composite under visible light irradiation, the photo-catalytic activity was evaluated and the results show that the CHC/C-PVA/TiO2composite has an enhanced photo-catalytic activity when compared to the CHC/TiO2 composite. Besides, the CHC/C-PVA/TiO2 shows a good photo-catalytic stability after the fourth cycles. The structure analyses by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) show the coexistence of C-PVA and TiO2 on the CHC and the cracks on the surface of CHC/C-PVA/TiO2. Result of ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS) reveals that the CHC/C-PVA/TiO2 can absorb both ultraviolet and visible light while result of X-ray photoelectron spectroscopy (XPS) indicates the existence of C, O and Ti elements in the CHC/C-PVA/TiO2. The typical structures as well as the optical characteristics of the CHC/C-PVA/TiO2 are responsible for the enhancement in the photo-catalytic activity.

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Evaluation of multi-cycle performance of chemical looping dry reforming using CO2 as an oxidant with Fe-Ni bimetallic oxides Zhen Huang, Huanqi Jiang, Fang He, Dezhen Chen, Guoqiang Wei, Kun Zhao, Anqing Zheng, Yipeng Feng, Zengli Zhao, Haibin Li 2016, 25(1): 62-70.  DOI: 10.1016/j.jechem.2015.10.008 摘要 ( 4407 )   Chemical looping dry reforming (CLDR) is an innovative technology for CO2 utilization using the chemical looping principle. The CLDR process consists of three stages, i.e. CH4 reduction, CO2 reforming, and air oxidation. Spinel nickel ferrite (NiFe2O4) was prepared and its multi-cycle performance as an oxygen carrier for CLDR was experimentally investigated. X-ray diffraction (XRD) and Laser Raman spectroscopy showed that a pure spinel crystalline phase (NiFe2O4) was obtained by a parallel flow co-precipitating method. NiFe2O4 was reduced into Fe-Ni alloy and wustite (FexO) during the CH4 reduction process. Subsequent oxidation of the reduced oxygen carrier was performed with CO2 as an oxidant to form an intermediate state: a mixture of spinel Ni1+xFe2-xO4, Fe2+yO4 and metallic Ni. And CO was generated in parallel during this stage. Approximate 185 mL of CO was generated for 1 g spinel NiFe2O4 in a single cycle. The intermediate oxygen carrier was fully oxidized in the air oxidation stage to form a mixture of Ni1+xFe2-xO4 and Fe2O3. Although the original state of oxygen carrier (NiFe2O4) was not fully regenerated and agglomeration was observed, a good recyclability was shown in 10 successive redox cycles.

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Ethanol electrooxidation on Pd/C nanoparticles in alkaline media Fangfang Zhang, Debi Zhou, Mingda Zhou 2016, 25(1): 71-76.  DOI: 10.1016/j.jechem.2015.10.013 摘要 ( 6090 )   Carbon-supported Pd nanoparticleswere prepared bymicrowave heating-glycol reductionmethod, and characterized by a wide array of experimental techniques including X-ray diffraction spectroscopy (XRD) and transmission electron microscopy (TEM). The electrooxidation behaviors of ethanol on the Pd/C electrode in alkaline media were investigated using cyclic voltammetry (CV), chronoamperometry (CA), electrochemical impedance spectroscopy (EIS) and single cell performance methods. Pd/C electrode for ethanol oxidation showed high electro-catalytic activity and long term stability. However, it is observed that the current density decreases with the increasing of the potential and negative impedance presents in the potential from -0.1 to 0.1 V. The decreasing current density and the negative impedance could be due to the adsorbed intermediates species that inhibited the further oxidation of ethanol. Based on the chemical reaction analysis and EIS spectra, equivalent circuits relating to various potential zones have been obtained. These results reveal the dynamic adsorption of intermediates species on Pd surfaces. Significantly, it is clarified that the adsorption behavior begins from the maximum catalysis of electro-catalysis and ends in the formation of the palladium (II) oxide layer on the electrode surface.

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Enhancement of current density using effective membranes electrode assemblies for water electrolyser system Swaminathan Seetharaman, Subash Chandrabose Raghu, Kambiz Ansari Mahabadi 2016, 25(1): 77-84.  DOI: 10.1016/j.jechem.2015.08.010 摘要 ( 4350 )   The goal of this study was to develop and design a composite proton exchange membrane (PEM) and membrane electrode assembly (MEA) that are suitable for the PEM based water electrolysis system. In particular, it focuses on the development of sulphonated polyether ether ketone (SPEEK) based membranes and caesium salt of silico-tungstic acid (CsSiWA) matrix compared with one of the transition metal oxides such as titanium dioxide (TiO2), silicon dioxide (SiO2) and zirconium dioxide (ZrO2). The resultant membranes have been characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, ion exchange capacity (IEC), water uptake and atomic force microscopy. Comparative studies on the performance of MEAs were also conducted utilizing impregnation-reduction and conventional brush coating methods. The PEM electrolysis performance of SPEEK-CsSiWA-ZrO2 composite membrane was more superior than that of other membranes involved in this study. Electrochemical characterization shows that a maximum current density of 1.4 A/cm2 was achieved at 60 ℃, explained by an increased concentration of protonic sites available at the interface.

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Effects of Cs-substitution and partial reduction on catalytic performance of Keggin-type phosphomolybdic polyoxometalates for selective oxidation of isobutane Shizhe Liu, Lu Chen, Guowei Wang, Jianwei Liu, Yanan Gao, Chunyi Li, Honghong Shan 2016, 25(1): 85-92.  DOI: 10.1016/j.jechem.2015.11.004 摘要 ( 6166 )   The catalytic performance of Cs-substituted phosphomolybdic salts was studied for selective oxidation of isobutane. The results of activity tests revealed that 360 ℃ was the optimal reaction temperature. It was demonstrated that oxidizing sites not only took dominating part in the activation of isobutane, but also influenced the product distribution. Besides, appropriate Cs addition led to moderate acidity of catalysts, favoring the selectivity to desired products. Furthermore, to obtain partially reduced catalysts, different calcination atmospheres were investigated and certain proportion of Mo5+ produced during calcination was crucial for the redox reaction. The catalyst calcined in N2 showed the highest yield of MAA (7.0%). Fe-substitution enhanced the activity of catalysts by rapid reoxidation of Mo5+.

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Electrochemical performance of all-solid lithium ion batteries with a polyaniline film cathode Ji-Woo Oh, Rye-Gyeong Oh, Yongku Kang, Kwang-Sun Ryu 2016, 25(1): 93-100.  DOI: 10.1016/j.jechem.2015.08.008 摘要 ( 4209 )   We have prepared a high-density polyaniline (PANI) paste (50 mg/mL), with similar physical properties to those of paints or pigments. The synthesis of PANI is confirmed by Fourier transform infrared (FT-IR) spectroscopy. The morphologies of PANI, doped PANI, and doped PANI paste are confirmed by scanning electron microscopy (SEM). Particles of doped PANI paste are approximately 40-50 nm in diameter, with a uniform and cubic shape. The electrochemical performances of doped PANI paste using both liquid and solid polymer electrolytes have been measured by galvanostatic charge and discharge process. The cell fabricated with doped PANI paste and the solid polymer electrolyte exhibits a discharge capacity of ~87 μAh/cm2 (64.0 mAh/g) at the second cycle and ~67 μAh/cm2 (50.1 mAh/g) at the 100th cycle.

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Cycle performance of Cu-based oxygen carrier based on a chemical-looping combustion process Xiaoming Zheng, Lixin Che, Yanqiong Hao, Qingquan Su 2016, 25(1): 101-109.  DOI: 10.1016/j.jechem.2015.10.011 摘要 ( 4120 )   The cycle life of oxygen carrier (OC) is crucial to the practical applications of chemical looping combustion (CLC). Cycle performance of Cu/SiO2 prepared with a mechanical mixing method was evaluated based on a CLC process characterized with an added methane steam reforming step. The Cu/SiO2 exhibited high redox reactivity in the initial cycles, while the performance degraded with cycle number. Through characterization of the degraded Cu/SiO2, the performance degradation was mainly caused by the secondary particles' fragmentation and the fine particles' local agglomeration, which worsened the distribution and diffusion of the reactive gases in the packed bed. A regeneration method of the degraded OC based on re-granulation has been proposed, and its mechanism has been illustrated. With this method, the performance of the degraded OC through 420 redox cycles was recovered to a level close to the initial one.

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Simultaneous recovery of carbon and sulfur resources from reduction of CO2 with H2S using catalysts Hui Su, Yuyang Li, Ping Li, Yongxiu Chen, Zhizhi Zhang, Xiangchen Fang 2016, 25(1): 110-116.  DOI: 10.1016/j.jechem.2015.08.009 摘要 ( 4238 )   An approach to the simultaneous reclamation of carbon and sulfur resources from CO2 and H2S has been proposed and effectively implemented with the aid of catalysts. A brief thermodynamic study reveals the potential of direct reduction of CO2 with H2S (15:15 mol% balanced with N2) for selective production of CO and elemental sulfur. The experiments carried out in a fixed-bed flow reactor over the temperature range of 400-800 ℃ give evidence of the importance of the employment of catalysts. Both the conversions of the reactants and the selectivities of the target products can be substantially promoted over most catalysts studied. Nevertheless, little difference appears among their catalytic performance. The results also prove that the presence of CO2 can remarkably enhance H2S conversion and the sulfur yield in comparison with H2S direct decomposition. A longtime reaction test onMgO catalyst manifests its superior durability at high temperature (700 ℃) and huge gas hourly space velocity (100, 000 h-1). Free radicals initiated by catalysts are supposed to dominate the reactions between CO2 and H2S.

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Selective oxidation of biomass derived 5-hydroxymethylfurfural to 2, 5-diformylfuran using sodium nitrite Xianxiang Liu, Hui Ding, Qiong Xu, Wenzhou Zhong, Dulin Yin, Shengpei Su 2016, 25(1): 117-121.  DOI: 10.1016/j.jechem.2015.08.012 摘要 ( 3772 )   A mild and simple process for the effective oxidation of 5-hydroxymethylfurfural (HMF) into 2, 5- diformylfuran (DFF) has been developed using NaNO2 as the oxidant. Some important reaction parameters were investigated to optimize the oxidation of HMF into DFF. It was found that the reaction solvent was very crucial for this reaction. Trifluoroacetic acid was the best solvent for the oxidation of HMF into DFF by NaNO2. Under the optimal reaction condition, almost quantitative HMF conversion and high DFF yield of 90.4% were obtained after 1 h at room temperature.