Fe(Ⅱ)-Cr(Ⅲ)电解液在石墨电极上的氧化还原动力学研究

Redox kinetics of Fe(Ⅱ)-Cr(Ⅲ) hybrid electrolyte on graphite electrode

为明晰电极对铁铬液流电池电极反应的影响因素,利用循环伏安、极化曲线和交流阻抗方法研究Fe(Ⅱ)-Cr(Ⅲ)电解液在石墨电极上的氧化还原动力学,计算出其电极反应动力学参数:扩散系数Do=7.98×10^-6 cm^2/s;反应速率常数k°=9.15×10^-4cm/s;交换电流密度Jo=2.7×10^-3 A/cm^2.结果 表明,Fe(Ⅱ)-Cr(Ⅲ)电解液在石墨上的电极反应主要受扩散控制;电极材料会使Fe^2+/Fe^3+离子电对的电极反应速率产生数量级上的差距;在实现大电流密度过程中,铁铬体系对电极材料的要求有别于全钒体系.

In order to ensure the factors affecting the electrode reaction of Fe/Cr redox flow battery, the redox kinetics of the Fe (Ⅱ)-Cr (Ⅲ) hybrid electrolyte on graphite electrode was investigated by means of cyclic voltammetry, polarization curve and electrochemical impedance spectroscopies. The kinetics parameters of the Fe (Ⅱ)-Cr (Ⅲ) hybrid electrolyte were calculated. The diffusion coefficient is 7.98×10^-6cm^2/s, the reaction rate constant is 9.15× 10^-4 cm/s, and the exchange current density is 2.7×10^-3A/cm^2. The results show that the reaction of Fe (Ⅱ)-Cr (Ⅲ) hybrid electrolyte on graphite electrode is mainly controlled by diffusion. The reaction rate constant of Fe^2+/Fe^3+ couple on graphite and Pt electrode decreases by one order of magnitude. The requirement for electrode materials of Fe/Cr redox system is different from that of all vanadium redox system in the implementation process of high current density.