Application of pattern recognition techniques to qualitative electrochemical analysis: Part II. On-line measurements of double-layer capacity by the superimposition method and adaptive compensation of charging current by the capacitance multiplier

Abstract

A random voltage signal with a larger amplitude for the faradaic electrolysis, on which a high-frequency small sinusoidal ac voltage signal is superimposed, has been used as a input signal. The response current of the ac voltage signal consists of the charging current. Gain values and phase values of the electrochemical double layer, which are obtained by comparison of input and output of the high-frequency signal, are located against the sample value of the electrode potential ( E) at each moment using a microcomputer, and the images of both E−C dl (gain) and E− (phase) patterns come out gradually in the memory of the microcomputer, where C dl is the double-layer capacity and θ is the phase difference. The gain values are used for the control of the capacitance multiplier, which becomes an accurate and real-time simulator of the practical electrochemical double layer at the different electrode potential. An adaptive and real-time compensation of the charging current has been achieved merely by the analog subtraction of the current flowing through the capacitance multiplier (only the low-frequency potentiostatic signal is applied to its input terminal) instantaneously from the low-frequency response current.