Ti/Ir_xSn_(1-x)O_2电极的交流阻抗谱法研究

Study on the Electrochemical Impedance Spectroscopy of Ti/Ir_xSn_(1-x)O_2 Electrodes

采用交流阻抗谱法研究了IrxSn1-xO2复合氧化物电极在0.5 mol/L的H2SO4溶液中的电化学行为.用等效电路LRs(RfCf)(RctCdl)对交流阻抗谱的结果进行拟合.结果表明:当电位为0.3 V时电极反应与理想极化电极的阻抗图谱相近,以电容为主.而当电位为0.85 V时,电极受溶液电阻Rs,传荷电阻Rct,双电层电容Cdl,溶液浓度和扩散等多因素影响.Rs几乎与电位无关,其值在0.8～1.1Ω之间,Rct随着电位增大而减小.电极双电层在0.8～0.9 V时与活性点吸附OH有关,高于0.9 V后强烈的析氧反应开始,Tafel斜率继续增大,属于电化学极化和浓差极化同时控制.当电极成分比例为30%molIrO2+70%molSnO2时,电催化活性点的数量为最大.

The electrochemical characteristics of IrxSn1-x 02 electrodes were investigated by ac impedance technique in 0.5 mol/L H2 SO4 solution. An equivalent circuit of LRs （Rf Ccl） （Rct, Cdl） combination was used to fit the experimental data. When the applied potential is 0.3 V, the impedance behavior of electrode reac- tion is close to that of the ideal polarized electrode. It is mainly attributed to the double layer capacitance of the oxide/electrolyte interface. When the potential is up to 0.85 V, the electrode process is affected by more factors such as the resistance of solution （Rs）, the charge transfer resistance （Rot） , double-layer capacitance （Cdl）, solution concentration and diffusion. Rs is almost independent on the applied potential and the value keeps between 0.8 and 1.1Ω. Rct decreases with the increasing potential. The double layer charging involves the adsorption of OH in active sites with the potential in the range of 0.8 to 0.9 V. When the potential ex- ceeds 0.9 V, the intent oxide evolution begins and the Tafel slope increases. It＇ s controlled by electrochemical polarization and concentration polarization. The coating of 30 % IrO2 ＋ 70 % SnO2 exhibits the maximum elec- trochemical active ,;urfaee area.