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  • 2010-2014  (2,847)
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  • 1
    Publication Date: 2014-12-29
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Fei Li , Yu Xin Zhang , Ming Huang , Yuan Xing , Li Li Zhang Three-dimensional (3D) porous MnO 2 array assembled from one-dimensional tubular MnO 2 with ultrathin sheets were fabricated by a one-pot hydrothermal method using polycarbonate membrane as the template. The diameter and thickness of nanotubes can be controlled by the membrane. Detailed electrochemical characterization reveals that the porous MnO 2 arrays exhibited good rate performance and cycle life. The highest specific capacitance in a three-electrode system was 411.9 F g −1 at a current density of 0.25 A g −1 . An asymmetric supercapacitor with porous MnO 2 nanotubes arrays as the positive electrode and activated graphene as the negative electrode yielded an energy density of 22.6 Wh kg −1 at a power density of 225.3 W kg −1 . The capacitive performance was correlated with the hierarchical structure of the porous MnO 2 nanotubes. Graphical abstract
    Print ISSN: 0013-4686
    Electronic ISSN: 1873-3859
    Topics: Chemistry and Pharmacology , Physics
    Published by Elsevier
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  • 2
    Publication Date: 2014-12-29
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Nianxing Wang , Anniina Kähkönen , Pia Damlin , Timo Ääritalo , Jouko Kankare , Carita Kvarnström In this work two three-branched cyanopyridine based monomers were synthesized and used as starting materials for the preparation of viologen derivatives with branched structures. The film synthesis was performed using reductive electropolymerization in aqueous solution. Both electrochemical and spectroelectrochemical characterization proved that the viologen films undergo a well-defined and reversible two step redox reaction, which is the typical performance for viologen materials. Furthermore, FTIR and SEM were utilized to characterize their structures and morphologies. SEM studies showed that the viologen films have a highly porous structure. Additionally, discharging experiments confirmed that the viologen films show different intercalation behavior as size of electrolyte anion had various effects on the redox potential. Finally, it has been proven that these two viologen derivative materials have the potential to be utilized as a supporting material with intrinsic redox activity and with excellent properties for hosting especially negatively charged particles, molecules and macromolecules. The promising properties of these materials make them good candidates in electronics and also in organic solar cells when loaded with large molecules such as fullerenes. In the organic rechargeable battery applications they can be used as anode-active materials as they exhibit high charging-discharging capacity at negative potentials.
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    Electronic ISSN: 1873-3859
    Topics: Chemistry and Pharmacology , Physics
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  • 3
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Rong-Hua Liu , Wen-Wei Li , Guo-Ping Sheng , Zhong-Hua Tong , Michael Hon-Wah Lam , Han-Qing Yu Bioelectrochemical systems have been intensively studied as a promising technology for wastewater treatment and environment remediation. Coupling of the anodic and cathodic electrochemical reactions allows an enhanced degradation of recalcitrant organics, but external power supply is usually needed to overcome the thermodynamic barrier. In this work, we report a self-driven degradation of azobenzene in a microbial fuel cell (MFC), where the cathodic reduction of azobenzene was effectively coupled with the anodic oxidation of its reduction degradation intermediate (i.e., aniline). The anodic degradation rate of aniline, as the sole carbon source, was significantly higher than that under open-circuit conditions, suggesting a considerable bioelectrochemical oxidation of aniline. Output voltages up to 8 mV were obtained in the MFC. However, a shift of cathodic electron acceptor from oxygen to azobenzene resulted in a decreased aniline degradation rate and output voltage. The present work may provide valuable implications for development of sustainable bioelectrochemical technologies for environmental remediation. Graphical abstract
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    Topics: Chemistry and Pharmacology , Physics
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  • 4
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Hadi Beiginejad , Ameneh Amani , Davood Nematollahi , Sadegh Khazalpour Electrochemical oxidation of some aminophenol derivatives ( 1–5 ) has been investigated both experimentally and theoretically. Experimental results were obtained using cyclic voltammetry and controlled potential coulometry. The theoretical results were calculated at DFT (B3LYP and BP86) levels of theory and 6-311 + G (p,d) basis sets. Using a general thermodynamic cycle, the calculated ΔG tot of the oxidation of the studied aminophenol derivatives indicates that thermodynamic is one of the important parameters on the potential oxidation. The obtained results show that electrochemical oxidation potential of 1–5 is directly dependent on the ΔG tot of electrochemical oxidation. In addition in this paper, mechanisms of the electrochemical oxidation of 4-(piperazin-1-yl) phenol ( 6 ) in the presence of various nucleophiles was studied in viewpoint of the thermodynamic. Mechanistic study of the electrochemical oxidation of 6 in the presence of different nucleophiles indicates that although the electrochemical oxidations of 6H + in the presence of different nucleophiles have different mechanisms but proceed in the thermodynamically favored directions.
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    Topics: Chemistry and Pharmacology , Physics
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  • 5
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Xiaoe Xie , Zhanhong Yang , Zhaobin Feng , Zheng Zhang , Jianhang Huang Zn-Al layer double hydroxides (LDHs) were prepared through a simple hydrothermal method and proposed as an anode additive for Zn/Ni alkaline secondary batteries. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) of sample LDHs indicates that LDHs was well prepared. The electrochemical properties of the ZnO anodes with different contents of Zn-Al-LDHs were investigated by galvanostatic charge-discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscope (EIS). The structures and morphologies after cycles were also measured by SEM. The results indicate that the presence of Zn-Al-LDHs in the electrode exhibits better electrochemical performance compared with the pure ZnO electrode, such as superior electrochemical cycle stability, better reversibility and higher discharge capacity and utilization ratio. Especially for the electrode added with 24% Zn-Al-LDHs, the discharge capacity hardly declined over 250 cycles, the average utilization ratio could reach 98.5%, and the electrode had no obvious shape change and Zn dendrites after the cycling tests.
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    Electronic ISSN: 1873-3859
    Topics: Chemistry and Pharmacology , Physics
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  • 6
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Yun Guang Zhu , Ye Wang , Jian Xie , Gao-Shao Cao , Tie-Jun Zhu , Xinbing Zhao , Hui Ying Yang In this work, SnO 2 quantum dots and graphene (G) nanocomposites (SnO 2 /G) were synthesized via a facile one-step hydrothermal method for the application of anode material in lithium ion batteries (LIBs). SnO 2 quantum dots with a diameter ranging from 5 to 10 nm were uniformly anchored on graphene nanosheets. SnO 2 /G nanocomposites can deliver high specific capacities of 860 mAh g −1 after 50 cycles at a current density of 200 mA g −1 , and 683 mAh g −1 at a current density of 1600 mA g −1 . Compared to the pure SnO 2 , the excellent improved electrochemical performance of SnO 2 /G nanocomposites for lithium ion storage can be attributed to the stable structure and the improved electron conduction channel provided by graphene with functional groups (FGs), such as C-OH, C=O and C-OOH. In order to further improve the SnO 2 /G nancomposites electrochemical performance, carbon thin layers were coated by the reduction of C 2 H 2 gas via CVD technology (SnO 2 /G-C). However, SnO 2 /G-C showed an inferior performance compared to that of the SnO 2 /G without carbon coating. Through X-ray photoelectron spectroscopy (XPS) analysis, it was found that function groups play a critical role on the stability of SnO 2 /G nanocomposites. Such observation may thus instruct the design and implementation of graphene/metal oxides nanocomposites for high-performance LIBs anode materials.
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    Electronic ISSN: 1873-3859
    Topics: Chemistry and Pharmacology , Physics
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  • 7
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): A.G. Zelinsky The anodic current in individual and mixed thiosulfate-sulfite solutions was studied by means of voltammetry on a fresh gold RDE surface. An unexpected result was obtained: a new additional current maximum appears on the anodic voltammogram in mixed solutions; it is not observed in the individual solutions of sodium thiosulfate and sulfite. The reasons for, and mechanism associated with, this phenomenon require separate and detailed investigation. It is shown that the rate of the anodic process in sulfite solutions is limited by diffusion of discharging particles, while the rate of the anodic process in thiosulfate solutions is limited by slow (in comparison with diffusion) heterogeneous reactions. In mixed solutions, the presence of thiosulfate causes partial passivation of the electrode, while the presence of sulfite causes its partial depassivation. It is stressed that the initial stages of oxygen evolution on gold have opposite effects on anodic currents in sulfite and thiosulfate solutions.
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    Topics: Chemistry and Pharmacology , Physics
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  • 8
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Akbar Shabanikia , Mehran Javanbakht , Hossein Salar Amoli , Khadijeh Hooshyari , Morteza Enhessari In this work, perovskite-type SrCeO 3 nanoparticles were used for improving the properties of high temperature polybenzimodazole (PBI) based proton exchange membranes. Novel proton conducting membrane nanocomposites were prepared using different amounts of SrCeO 3 nanopowders dispersed into by solution casting method.The nanocomposite membranes were studied by using AC impedance spectroscopy, scanning electron microscopy coupled with energy dispersive X-ray and thermo gravimetric analysis. The prepared nanocomposite membranes showed a higher acid uptake, proton conductivity and thermal stability compared with the pure PBI membranes. The highest acid uptake (190%) and proton conductivity (0.105 S/cm at 180 °C and 0% RH) were observed for phosphoric acide-dopped PBI nanocomposite membranes containing 8 wt% of SrCeO 3 nanoparticles (PSC 8 ). The PSC 8 nanocomposite membranes were tested in a fuel cell and the polarization and power curves were obtained at different temperatures. The PSC 8 showed 0.44 W/cm 2 power density and 0.88 A / cm 2 current density in 0.5 V at 180 °C. The result obtained from our studies shows the enhanced potential of the PSC 8 as proton exchange membranes for high temperature proton exchange membrane fuel cells.
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  • 9
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Narendar Nasani , Devaraj Ramasamy , Isabel Antunes , Jose Perez , Duncan P. Fagg The matrix phase of protonic ceramic fuel cell (PCFC) cermet anodes potentially plays a vital role in hydrogen oxidation kinetics. The present work aims to investigate such involvement by selecting ceramic-oxide matrices with widely dissimilar levels of proton conduction. The materials chosen were that of the proton conducting phase BaZr 0.85 Y 0.15 O 3-δ and the nominal composition BaZrO 3 of negligible proton conduction. Cermet anodes Ni-BaZrO 3 and Ni-BaZr 0.85 Y 0.15 O 3-δ were synthesized by the acetate-H 2 O 2 combustion method for Ni contents of 40 vol%. The microstructure and electrochemical performance of the cermet anodes were investigated by scanning electron microscopy (SEM) and electrochemical impedance measurements (EIS) respectively. The polarisation behaviour of the two nickel cermet anodes was studied as a function of temperature, hydrogen partial pressure (pH 2 ) and water vapor partial pressure (pH 2 O). The results confirm that polarisation resistance is highly sensitive to the composition of the ceramic phase of the cermet anode and that the higher frequency electrode response exhibits strong links to levels of proton transport in the ceramic-oxide matrix.
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  • 10
    Publication Date: 2014-12-26
    Description: Publication date: 1 February 2015 Source: Electrochimica Acta, Volume 154 Author(s): Jinle Shi , Zonghua Pu , Qian Liu , Abdullah M. Asiri , Jianming Hu , Xuping Sun It is highly desired but still remains a challenging task to develop efficient non-noble-metal hydrogen evolution reaction (HER) electrocatalysts operating efficiently under all pH conditions. In this paper, tungsten nitride nanorods array was developed on carbon cloth (WN NA/CC) through nitridation of corresponding WO 3 NA/CC precursor with NH 3 as an efficient 3D hydrogen evolution cathode with strong durability in acidic solutions. It needs overpotential of 198 mV to achieve current density of 10 mA cm −2 and it maintains its catalytic activity for at least 60 h. This electrode also performs well under both neutral and alkaline conditions. In addition, this electrode shows nearly 100% Faradaic efficiency at all pH values.
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    Topics: Chemistry and Pharmacology , Physics
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