Kinetic studies at carbon felt electrodes for vanadium redox-flow batteries under controlled transfer current density conditions
Kinetic studies at carbon felt electrodes for vanadium redox-flow batteries under controlled transfer current density conditions
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DOI：
10.1016/j.electacta.2017.07.062
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发表时间：
2017-10-20
影响因子：
6.6
通讯作者：
Turek, Thomas
中科院分区：
文献类型：
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作者：
Becker, Maik;Bredemeyer, Niels;Turek, Thomas
在这项工作中，我们提出了数学模型和实验动力学表征相结合的碳毡电极在正极电解液(PE)和负极电解液(NE)的钒氧化还原液流电池。该数学模型被应用于检查由电解液密集流过的径向连接的碳电极内的均匀转移电流密度。转移电流的均匀性主要取决于电解液的电导率、电极厚度和电荷转移系数。当使用单层碳电极(415 mm厚，孔隙率为89%，210 mm厚，孔隙率为75%)，并通过低钒浓度(<；15 mm)保持高的电解液电导率(>；800mS.cm(-1))时，所研究的电极样品的转移电流不均匀性低于5%。实验结果表明，在高过电位下，NE还原反应的电荷转移系数为0.26+/-0.03，NE氧化反应的电荷转移系数为0.37+/-0.04。PE还原反应的电荷转移系数为0.13+/-0.02，氧化反应的电荷转移系数为0.30+/-0.04。用Butler-Volmer方程描述了材料的极化行为，在25%~75%的电荷态范围内与实验结果吻合较好。PE反应的速率常数比NE反应的速率常数大近两倍。(C)2017爱思唯尔有限公司。保留所有权利。
In this work we present a combination of mathematical modeling and experimental kinetic characterization of carbon felt electrodes in positive electrolyte (PE) and negative electrolyte (NE) of vanadium redox-flow batteries. The mathematical model is applied to check for homogeneous transfer current density within a radially connected carbon electrode intensively flown through by the electrolyte. Transfer current homogeneity depends mainly on electrolyte conductivity, electrode thickness and charge transfer coefficient. The transfer current inhomogeneity of the investigated electrode samples is below 5%, when single layers of carbon electrodes (415 mm thickness at 89% porosity and 210 mm thickness at 75% porosity) are applied and high electrolyte conductivities (>800 mS.cm(-1)) are maintained by low vanadium concentrations (< 15 mM). Experimental results show charge transfer coefficients for high overpotentials of 0.26 +/- 0.03 for the reduction reaction in NE and 0.37 +/- 0.04 for the oxidation reaction in NE. The charge transfer coefficients of the PE are 0.13 +/- 0.02 for reduction and 0.30 +/- 0.04 for the oxidation reaction. Application of the Butler-Volmer equation to describe the polarization behavior shows adequate agreement with the experimental results at states of charge between 25% and 75%. The rate constants for the PE reaction are nearly two times higher than for the NE reaction. (C) 2017 Elsevier Ltd. All rights reserved.