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    25 August 2017, Volume 23 Issue 4
    Special issue on theoretical and computational electrochemistry(Editor: Prof. Jun Cheng)
    Preface for special issue on theoretical and computational electrochemistry
    CHENG Jun
    2017, 23(4):  369-370.  doi:10.13208/j.electrochem.170140
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    Electrochemistry, an old branch of science, has a long and glorious history. It has become again an exciting and vibrant research field. Recently, tremendous attentions have been paid on electrochemcistry because of its close relevance to energy and environment related issues that have caused wide public concerns and received attentions from many governments. Many important energy systems and devices, including energy conversion and storage, as well as solar energy utilization, involve electrochemical processes that traditionally fall into the research themes of electrochemistry.
    Surface Chemical Properties of Mo2C, W2C, Mo2N and W2N Probed with CO, CO2and O2 Adsorption: A DFT Analysis
    YE Jingyun, ZHANG Tianyu, XU Lingyun, YIN Shuxia, WEERASINGHE Krishanthi, UBALDO Pamela, HE Ping and GE Qingfeng
    2017, 23(4):  371-380.  doi:10.13208/j.electrochem.170141
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    Transition metal carbides and nitrides are attractive materials for electrodes in many electrochemical energy storage and conversion applications. In the present study, we use density functional theory slab calculations to characterize the surface chemical properties of molybdenum (Mo) and tungsten (W) carbides and nitrides, namely, Mo2C, W2C, Mo2N and W2N with the adsorption of CO, CO2 and O2. These probing molecules provide measures of in both acidity/basicity and redox property of for the surfaces of these carbides and nitrides. Our results show that Lewis basic sites were responsible for CO2 adsorption and the basicity follows followed an order of α-W2C(001) > α-W2N(001) > β-Mo2C(001) > γ-Mo2N(100). Both CO and O2 adsorption provide measures of in the reducing ability of these carbides and nitrides. The results showed a reducing ability in the order of β-W2C(100) > α-Mo2C(100) > α-W2N(001) > α-W2C(001) > β-Mo2C(001) > γ-Mo2N(100). The reducing nature of these carbides and nitrides make them good candidates to substitute noble metals in various catalytic reactions.
    Density functional investigation on cathode/electrolyte interface in solid-state lithium batteries
    Xuelong Wang, Ruijuan Xiao, Yong Xiang, Hong Li and Liquan Chen
    2017, 23(4):  381-390.  doi:10.13208/j.electrochem.170142
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    The rapidly expanding application of lithium ion batteries stimulates research interest on energy storage devices with higher energy density, better safety and faster charge/discharge speed. All-solid-state lithium batteries have been considered as promising candidates because of their fewer side reactions and better safety compared with conventional lithium-ion batteries with organic liquid electrolytes. Looking for well-matched electrode/electrolyte interfaces is one of the keys to ensuring good comprehensive performance of solid-state lithium batteries. In this report, with the aid of first-principles simulations, the local structure and lithium ions transportation properties of electrolyte surfaces and cathode/electrolyte interfaces are investigated. The β-Li3PS4 (010)/LiCoO2 (104) and Li4GeS4(010)/LiCoO2(104) interfaces are adopted as model systems to understand the bonding interaction and Li+ migration barriers at interfaces. The ability of Li+ motion is improved in partial delithiated state for both systems, due to that Co atoms at the interface in high oxidized state oxidize the S atoms nearby and weaken the P/Ge-S bond resulting in less constrains on Li ions in neighbor and promoting the exchange of Li ions across the interface. It provides information for cathode/electrolyte interface optimization, and may help us discover appropriate techniques for solid-state lithium batteries.

    Electrostatic Interactions of Water in External Electric Field: Molecular Dynamics Simulations
    ZHU Qiang, KAN Zigui, MA Jing
    2017, 23(4):  391-399.  doi:10.13208/j.electrochem.170143
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    A series of molecular dynamics simulations with or without external electric field have been carried out for a bulk water with periodic boundary condition. The difference in radial distribution function of interatomic O…O distance is subtle, with and without external electric field, except for the orientation of dipole moments of water molecules. Without the applied external electric field, distribution of the orientation angle of dipole moments is rather broad. The induced local electric field is analyzed as a function of altitude in direction of electric field. The variation of the local induced electric field is increased as the increase of the external electric field. The local induced electrostatic energy is mainly originated from the increase in the ordering of dipole orientation under the external electric field. Dielectric constant is evaluated according to the fluctuation of total dipole moment of the whole system. The change of relative dielectric constant under the different external electric fields can be described in an exponential decay equation as the increase of the strength of electric field. This simple rule can be applied to understand the electrostatic interaction and local induced electric field under various electrochemical environments.

    Articles
    Thermo-stability and active site structure of Fe/N/C electrocatalyst for oxygen reduction reaction
    CHEN Chi, LAI Yu-jiao, ZHOU Zhi-you, ZHANG Xin-sheng, SUN Shi-gang
    2017, 23(4):  400-408.  doi:10.13208/j.electrochem.170324
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    The development of Fe/N/C electrocatalyst for oxygen reduction reaction (ORR) is vital for the large-scale applications of proton exchange membrane fuel cells. Understanding the active site structure will contribute to the rational design of highly active catalysts. In this study, the as-prepared Fe/N/C catalyst based on poly-m-phenylenediamine (PmPDA-FeNx/C) catalyst with the high ORR activity was subjected to the high-temperature heat treatment again at 1000 ~1500 oC. The degradation of in the ORR activity of PmPDA-FeNx/C by with various heat treatments was correlated to the change of elemental compositions, chemical states and textural properties. As the temperature elevated, the Fe atoms aggregated to form nanoparticles, while the gaseous N-containing species volatilized and the amount of N contents decreased, resulting in the destruction of active sites. The XPS analysis revealed that the content of N species with low binding energy show good positive correlation with the ORR kinetic current of catalyst, demonstrating that the pyridinic N and Fe-N species are probably main components of active sites and contribute to the high ORR activity. This study provides a new strategy to investigate the nature of active centre.
    Effects of surface modification modes on proton-over-vanadium ion selectivity of Nafion®membrane for application in vanadium redox flow battery
    Qinglong Tan, Haining Wang, Shanfu Lu, Dawei Liang, Chunxiao Wu, Yan Xiang
    2017, 23(4):  409-419.  doi:10.13208/j.electrochem.160307
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    The effect of surface modification modes on proton-over-vanadium ion selectivity was studied by spin-coating chitosan-Phosphotungstic Acid (PWA) as a single or double layer on Nafion membrane surface. To suppress the vanadium ions permeation through the Nafion? membrane in a vanadium redox flow battery (VRFB), the single surface-modified Nafion membrane (Nafion/chitosan-PWA)S and double surface-modified Nafion membrane (Nafion/chitosan-PWA)D demonstrated a 89.9% and 92.7% reduction of vanadium ion permeability in comparison with pristine Nafion, respectively. The (Nafion/chitosan-PWA)D exhibited betterhigher selectivity between proton and vanadium ions than the (Nafion/chitosan-PWA)S at the same layer thickness. Furthermore, the columbic efficiency for the VRFB single cell based on the (Nafion/chitosan-PWA)D at an optimized thickness was 93.5% and the energy efficiency was 80.7% at a charge-discharge current density of 30 mA·cm-2, which wereas higher than the (Nafion/chitosan-PWA)S and pristine Nafion membrane. The modified membranes also possessed adequate chemical stability in the VRFB during charge-discharge cycling measurements.
    An electrochemical dissolution study of ilmenite fraction of beach sand in sulphuric acid solution
    M. Rostom Ali, R. K. Biswas, Md. Golam Zakaria
    2017, 23(4):  420-428.  doi:10.13208/j.electrochem.160311
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    Electrochemical techniques have been used to investigate the dissolution behaviors of ilmenite fraction of beach sand of Bangladesh in sulfuric acid solutions at various temperatures. It is seen from the cyclic voltammetric studies indicated that the dissolution of ilmenite is was very difficult without the addition of carbon powder in ilmenite. The effects of ilmenite-carbon ratio, acid concentration and temperature on cyclic voltammograms have been investigated to understand the dissolution process of ilmenite. The investigated results showed that the dissolution rate of ilmenite (FeTiO3) is was slow at low applied reduction potentials and temperatures. However, the dissolution rate was increases accelerated at more negatively applied reduction potentials and higher temperatures. The dissolution rate was also increases increased with theon increasing acid concentrations up to 1 mol•dm-3; . and aAt more larger acid concentrations and higher reduction potentials, ithe dissolution rate was decreases decreased due to the starting of H2 gas evolution which eventually decreases reduced the active surface area of pellet by adsorption. The activation energy (Ea) is was evaluated to be 50±10  kJ•mol-1 in the higher temperature region, (htr) andwhile 15±5  kJ•mol-1 in the lower temperature region (ltr)., The value of activation energy suggestsing the process to be diffusion controlled process at the lower temperature regionltr and chemically controlled process at the higher temperature regionhtr.
    Electric current induced flow and electrocapillary deformation of liquid Wood alloy in NaOH aqueous solution
    ZHANG Guo-di,LIN Qiao-li, CHENG Jian-hong,CAO Rui
    2017, 23(4):  429-434.  doi:10.13208/j.electrochem.160411
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    The phenomena of the electric current induced flow and electrocapillary deformation for a liquid Wood alloy in a NaOH electrolyte were studied. Electrocapillary behaviors for the liquid Wood alloy in NaOH electrolytes by applying external low voltages were investigated. The electrode reaction (redox reaction) induced the formation or removing removal of an oxide film, and further caused the drop deformation by decreasing or increasing an interfacial tension. The same polar charge in the electric double layer would also decrease the interfacial tension. In order to maintain the stability of system, the contact area of the interface would be expanded, and which induced induces the drop deformation macroscopically. When the liquid metal was charged by the chemical reaction in the solution, the electric field force is became an effective way to drive its movement in the electrolyte.
    Tetrabutylammonium Hexafluorophosphate as Flame Retardant Additive for Lithium Ion Batteries
    ZHAO Qing, ZHANG Qian, FAN Jing-min, ZHENG Ming-sen, DONG Quan-feng
    2017, 23(4):  435-440.  doi:10.13208/j.electrochem.160419
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    Safety issues have been attracted more and more attentions due to the wide applications of lithium ion batteries. Introducing flame retardant additives are one of the effective strategies to improve the safety of lithium-ion batteries. In this paper, the tetrabutylammonium hexafluorophosphate (TBAPF6) as a flame retardant additive was added to the electrolyte as a flame retardant additive to enhance the safety of lithium ion batteries. The self-extinguishing time (SET) and ionic conductivities of the electrolytes with different TBAPF6 contents were investigated. It is found that TBAPF6 dramatically reduced the flammability of the electrolyte while slightly decreasing ionic conductivitiesconductivity. The electrochemistry electrochemical performances of graphite half cells with higher content of TBAPF6 showed poor compatibility between TBAPF6 additive and graphite anode due to the lack of stable SEI layer formation. But However, the LiCoO2/Graphite graphite full battery with 5% TBAPF6 showed good electrochemical performance and extraordinary thermal stability within 300 oC, representing demonstrating a good flame retardant additive of TBAPF6.
    An investigation of the synergistic effect between (1,3-Dioxolan-2-ylmethyl)–triphenylphosphonium bromide and iodide ion for the corrosion inhibition of zinc in citric acid
    M. Saadawy
    2017, 23(4):  441-455.  doi:10.13208/j.electrochem.151222
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    The effect of (1,3-Dioxolan-2-ylmethyl)-triphenylphosphonium bromide (DTPB) on the zinc corrosion in 0.5 mol·L-1 citric acid solution was investigated at 30 oC using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. An ecofriendly bath was used for acid cleaning of zinc, which has not been widely used in literatures. The results showed that DTPB could serve as an effective inhibitor for the zinc corrosion in a citric acid solution with the inhibition efficiency of 98.9% at the DTPB concentration of 3×10-3 mol·L-1. A synergistic effect between DTPB and potassium iodide (KI) enhanced the inhibition capability of DTPB, and better inhibition efficiency was achieved as compared with that by using DTPB alone. The synergism parameter had a value of 1.2 and was found to decrease with temperature. An inhibition mechanism is proposed by which KI acts as an adsorption mediator for bonding metal surface and DTPB.
    A New Type Carbon Composited Molybdenum Doped Vanadium Oxide Nanowires as a Cathode Material for Sodium Ion Batteries
    ZHANG Guang-rui, HU Li-qiang, ZHANG Bao-zhu
    2017, 23(4):  456-465.  doi:10.13208/j.electrochem.160428
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    In recent years, the development of lithium ion batteries (LIBs) has been limited due to the insufficient lithium resource and increasing cost. As a promising candidate, sodium ion batteries (SIBs) with the similar electrochemical mechanism and lower cost than LIBs are developing rapidly. However, as a result of the larger radius of Na+ compared with Li+, the crystalline structures of the most electrode materials are damaged severely during the intercalation of Na+, which limits the electrochemical properties of SIBs. Thus, developing new types of electrode materials for SIBs is particularly important. Among the cathode materials, the layered vanadium oxides are being widely studied. In this work, for the first time, we designed and synthesized a new type of carbon composited molybdenum doped vanadium oxide nanowires (MVO/C) with the excellent electrochemical performances. The highest capacity reached 135.9 mAh•g-1under 50 mA•g-1. After 75 cycles, there was still 82.6 mAh•g-1 with 71.8% capacity remaining. When the current density was first increased to 1000 mA•g-1 and then went back to 50 mA•g-1, a high reversible capacity of 111.5 mAh•g-1 was obtained. The results demonstrated that the new type of carbon composited molybdenum doped vanadium oxide nanowires with a ultra-high interlayer spacing is a promising material for sodium storage, providing a theoretical foundation for the further development of SIBs.
    Influence of Typical Anions in Seawater Environments on Corrosion Behaviors of 5083 Aluminum Alloy
    TU Yang-fan, FENG Li-ming, FANG Zhi-gang,LIU Hai-tao, JING Ming-hua, GUAN Yong
    2017, 23(4):  466-472.  doi:10.13208/j.electrochem.160614
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    The interaction effects of typical anions, namely, Cl-, HCO3- and SO42-, presented in seawater environments on corrosion resistance behaviors of AA5083 aluminum alloy have been studied. The corrosion resistances of the 5083 aluminum alloy in different simulated seawater environments were tested by factorial analysis method. The polarization curves, the corrosion potentials, corrosion current densities and the breakdown potentials were examined in different concentrations of Cl-, HCO3- and SO42-.The corrosion behavior was analyzed by electrochemical impedance spectroscopy (EIS). The results showed that both Cl-,  and HCO3- could accelerate the pitting corrosion. When the concentration of Cl-,  remained constant, the corrosion resistance of AA5083 aluminum alloy increased initially with an increase in the concentration of HCO3-,and then dropped dramatically at 70~90 mg•L-1, which displayed the best corrosion resistance performance. Afterwards, the corrosion resistance increased again. The corrosion current density of AA5083 aluminum alloy was not significantly affected by SO42- when the concentrations of Cl- and HCO3- became larger. Meanwhile, when the concentration of HCO3- was fixed, the charge-transfer resistance of AA5083 aluminum alloy at a lower Cl-concentration was smaller than that at a higher Cl- concentration, and the corrosive ions could easily penetrate the native oxide film by a redox reaction with the matrix.
    Electrochemical Performance of Sodium Difluoro(oxalato)borate as the Additive of Non-aqueous Electrolytes for Sodium-ion Batteries
    ZHANG Ding, Zhu Qin, WANG Ying, ZHAO Cheng-long, LIU Shi-bin, XU Shou-dong
    2017, 23(4):  473-479.  doi:10.13208/j.electrochem.160703
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    Sodium ion battery has attracted worldwide and intensive attention recently, while the adoption of electrolyte additives has been considered as one effective strategy to promote the cell performance. Within this work sodium difluoro(oxalato)borate (NaDFOB) was prepared and adopted as an additive for the general non-aqueous electrolyte formula of 1 mol·L-1 NaClO4/EC/PC (Vol: Vol=1:1), and the effects of the additive concentration on ionic conductivity and oxidization decomposition voltage were investigated in detail. In addition, the cell performance evaluated by NaNi0.5Mn0.5O2 as the cathode was also studied. It reveals that the addition of NaDFOB into the NaClO4/EC/PC electrolyte resulted in the significantly increased oxidation decomposition voltages from 4.6 V to 4.85 V, in spite of the slightly increased ionic conductivity, attributed to extra dissociated sodium salt NaDFOB. When the 0.025 mol·L-1 NaDFOB added electrolyte was used to support the operation of NaNi0.5Mn0.5O2 cathode, the initial irreversible capacity decreased from 22 mAh·g-1 to 9 mAh·g-1, and the capacity retention upon 200 cycles at 0.2 C-rate increased from 44.4% to 89.5%, with an average capacity fade of 0.06 mAh·g-1 per cycle. Therefore, the NaDFOB was proved to be an effective electrolyte additive for non-aqueous sodium ion batteries.

    Effects of Temperature on the Nucleation and Growth Mechanism of PbO2 Electrodeposition
    WANG Lei, XUE Juan-qin, YU Li-hua,TANG Chang-bin, BI Qiang
    2017, 23(4):  480-488.  doi:10.13208/j.electrochem.160707
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    In order to investigate the effects of temperature on the nucleation and growth of lead dioxide (PbO2), the in situ electrochemical depositions of PbO2 were carried out on the glassy carbon electrode at different temperatures, namely, 25℃,35℃, 45℃, 55℃, and 65℃.The cyclic voltammetric curves, the time-current and the time-potential curves,SEM images and XRD patterns of the PbO2 coatings deposited at different temperatures were obtained. The results showed that the PbO2 underwent nucleation and grew at different temperatures. The 3D continuous nucleation mode of PbO2 electrodeposition remained unchanged with the increase of temperature. However, the solution resistance during the deposition process was decreased. The nucleation rate and the crystal growth rate were both promoted by the increase of temperature. Before reaching the saturated nucleation density, the nucleation rate was accelerated,and the size of PbO2 particles was reduced. During the later stage of the deposition, once the saturated nucleation density was attained, the nucleation rate became prodimnant, which adversely influenced the crystal growth rate,and the coating was not conductive to the formation of small PbO2 particles. High temperature enhanced the oxygen evolution rate and increased the energy consumption. The average particle size of PbO2 obtained at 55 ℃ was the smallest one among the five temperatures tested.
    Latest and Hot Papers
    Latest and Hot Papers
    ZHUANG Lin
    2017, 23(4):  489-490.  doi:10.13208/j.electrochem.170152
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