Electrochemical Reduction of Oxygen at Platinum Electrodes in KOH Solutions ‐ Temperature and Concentration Effects

Abstract

Electrochemical reduction of oxygen has been studied in detail employing rotating disk and ring‐disk electrode techniques in aqueous solutions of various concentrations at various temperatures. Analysis of voltammetric results recorded at the rotating disk electrode (RDE) indicates that there are two clearly defined Tafel regions of low (60 mV/decade) and high Tafel slopes. In general, electrode kinetics improves and Tafel slopes of the low‐slope region decreases slightly as the basicity of the electrolyte solution increases. The rotating ring‐disk electrode (RRDE) results were analyzed according to a simple model for oxygen reduction, first proposed by Damjanovic et al. The model is in agreement with experimental results at lower concentrations of . Rate constants for oxygen reduction directly to and , and for to were calculated at four different disk electrode potentials. The rate constant of direct reduction of oxygen to increases with the overpotential, but the plots of rate constants for oxygen reduction to and for reduction vs. potential pass through a maximum at about 0.85V vs. DHE. All these rate constants are shown to be slightly dependent on temperature.