电极微分电容的交流阻抗测量方法

The Measurement for AC Impedance of Differential Capacity of Electrode

微分电容作为电极重要参数之一 ,它的测量对于揭示电极表面状态和某些电化学反应过程极为有利。在提供了交流阻抗测量微分电容方法的同时 ,筛选出了适合在无浓差极化条件下获得准确结果的数据处理方法。交流阻抗数据是通过测量已知参数的模拟电解池而获得的。通过对同一组实验数据分别用复数平面图法、Bode图法、阻抗频谱法 (实频特性法和虚频特性法 )、特征频率法进行处理 ,发现 :复数平面图法、阻抗频谱法在取得微分电容参数方面优于其他方法 ,尤其是复数平面图法在稀疏采样的情况下仍能保持较高的准确度。在频谱法中实频特性法选取低频数据点和虚频特性法选取高频数据点都有利于提高准确性。

As one of the important electrode parameters differential capacity is more suitable for investigating electrode surface state and some electrochemical processes. The method of measuring differential capacity using AC impedance technique is presented in this paper, at the same time, data processing methods having accurate result under the condition of no concentration polarization are provided. The impedance data are obtained by measuring the real equivalent electrical circuit having the defined parameters. Various methods of analysis of AC impedance data are discussed by analyzing the same experiment data. The methods include complex plane plot, Bode plot, frequency spectrum plot which is divided into real part plot, 1/(R_s-R_l) vs ω2, and image part plot,C_s vs 1/ω2(where R_l is the solution resistance, R_s is the series resistance, and C_s is the series capacitance )and characteristic frequency plot. Some facts were outlined: complex plane plot and the frequency spectrum plot may obtain better results than other methods. In addition, complex plane plot still keeps accuracy in case of sparse data point. Low frequency data points provide higher accurate differential capacity value when using real part plot while high frequency data points do the same when using image part plot.