Diffusion Conductivity of Electrode Processes under Conditions of Natural Convection

Abstract

The diffusion conduction σ = di /dη (where i is the current and η is the overvoltage) in reversible system [Fe(CN)6]3–/4– is measured by the electrochemical impedance method under isothermal and nonisothermal conditions of natural convection. Platinum disk electrodes 3 mm and 20 μm in diameter are used. For a macroelectrode under isothermal conditions, σ passes through a maximum near equilibrium and tends to zero at η → 0. Under nonisothermal conditions and for a microelectrode under isothermal conditions, σ achieves a maximum near equilibrium. These data correlate with the η dependence of the diffusion layer thickness and quantitatively agree with theory.