Frequency Responses of Molar Electrochemical Peltier Heat and Entropy Changes Analyzed as Thermometric Transfer Functions

Abstract

In honor of Prof. Dr. Fritz Scholz in his recent retirement.This work proposes a theoretical framework to obtain the frequency response of molar electrochemical Peltier heat and entropy changes induced by a modulated electrical signal. This is based on an internal energy balance developed for a working electrode thermistor in ac regime. Then, from an analysis that correlates the electrochemical impedance and the interfacial temperature variation, two new transfer functions that depend on the frequency named as entropy changes and molar electrochemical Peltier heat, are obtained. This strategy is tested in two electrochemical systems: the ferrocyanide/ferricyanide couple and the copper ions in an acid sulphate-chloride medium. Both systems are analyzed by dc thermometric measurements, electrochemical impedance spectroscopy and ac-thermometric experiments namely variation of interfacial temperature. As a result, and are obtained and their values are correlated to the relaxation processes involved in the electrochemical reaction. Additionally, a brief discussion is included concerning the differences between the classical dc thermoelectrochemical methodology and the proposed approach here.