Ti基IrO_2+Ta_2O_5阳极的电化学特性

ELECTROCHEMICAL CHARACTERISTICS OF Ti BASED IrO_2+Ta_2O_5 ANODES

测量了Ti基IrO2+Ta2O5混合氧化物涂层的电化学阻抗谱（EIS）,研究了Ti基IrO2+Ta2O5混合氧化物涂层阳极在H2SO4溶液中的电化学表面结构以及电化学行为.这种涂层阳极具有多层电化学结构,低频段的阻抗行为对应电极外表面/溶液界面的阻抗恃性,高频段对应内表面/溶液界面的电化学特性和电极的物理阻抗.在析氧电位下,由于析出氧气的冲击,电极表面的总反应面积增大,而且析出的氧气对电极表面的改性受表面涂层的组织形态影响很大.由于晶粒的最细化,这种改性作用在IrO2含量为70％时最为明显.制备温度的升高使氧化物电极的多孔结构变得不明显、致密度上升以及活性表面积下降.

Electrochemical surface structure and electrochemical performs of Ti based IrO2+Ta2O5 anodes in H2SO4 solution have been investigated by electrochemical impedance spectroscopy (EIS). Double-layer electrochemical structure of Ti based IrO2+Ta2O5 anodes was deduced, which the low-frequency region corresponding to the impedance behaviors of the interface between outer surface and electrolyte, and the high-frequency to those of inner surface. A general equivalent circuits RS(R1Q1) (R2Q2)L was suitable over a wild potential region. It was showed that after oxygen evolution the total reaction area on electrode surface intended to increase compared with that at double-layer potential for oxygen evolution. The modification of surface by evolving oxygen was greatly affected by the surface morphologies. The surface modification, resulting from the finest grains existed on surface, appeared to be most significant for the electrodes corresponding to a IrO2 content of 70% (mole fraction). With the increasing of preparation temperature, the double-layer structure became less obvious, compactness increases and active surface area decreases.