V(Ⅳ)/V(Ⅴ)电对在石墨毡与导电塑料复合电极上的反应机理(英文)

Reaction Mechanism of V(Ⅳ)/V(Ⅴ) Redox Couple at Graphite Felt Composite Electrode Bonded with Conductive Carbon Plastic

应用循环伏安、极化曲线和交流阻抗等电化学方法研究了V(Ⅳ)/V(Ⅴ)电对在石墨毡复合电极上反应的速控步骤.结果表明,V(Ⅳ)/V(Ⅴ)电对在石墨毡电极上的反应属准可逆过程,且氧化过程包含有后置化学转化步骤;该过程Tafel斜率的实验值为0.124,而理论计算的,以电化学步骤作为控制步骤的Tafel斜率约0.12,两者吻合很好,表明该氧化过程受电化学步骤控制;以等效电路拟合不同极化电位下的交流阻抗,得出该电化学反应阻抗远大于其他阻抗,意味着电化学过程可能是电极反应的控制步骤,与实验得到的极化曲线分析结果相一致.

The rate-determining step of V（ Ⅳ ） / V（ Ⅴ ） redox reaction was investigated at graphite felt （CF） composite electrode by various techniques： cyclic volta mmetry, polarization curve and impedance spectroscopy. Cyclic voltammetry analysis indicated that V（ Ⅳ ） / V（ Ⅴ ） redox reaction at GF electrode is quasi reversible. A certain chemical reaction step is suspected to follow the electron transfer step of this reaction. The Tafel slope value （0. 124） obtained from the polarization curve agrees well with theoretical value （0.12）, which supposing the electron transfer step was the rate-determining step. Impedance Spectroscopies at various potentials were studied and simulated by equivalent circuits. The impedance value of the electron transfer step modified is greatly higher than the others, which shows that the electron transfer step is the rate-determining step. This further confirms the conclusion obtained by polarization curve test.