A Superoxide Involved Oxygen Reduction Reaction Mechanism on a Glassy Carbon Electrode in Caustic Media

Abstract

In this work, a plain glassy carbon electrode has been investigated as a base platform to build a superoxide-ion-involved, 2-dimensional, multi-physics model to describe its oxygen reduction mechanism in caustic media. A rotating ring disk technique has been used to quantify the peroxide content and to compare the results predicted by a general multiphysics model, which was further used to extract the influencing kinetic parameters. There are three proposed models involving different mechanism combinations made up of: a sequential, single electron reduction of oxygen to superoxide, then to peroxide; a sequential two electron reduction of oxygen to peroxide followed by the final reduction to hydroxide; and a direct four electron reduction of oxygen straight to hydroxide. One model stands out to be the best description for the multistep oxygen reduction behavior of the glassy carbon electrode in 0.1 M KOH with very satisfactory results, which yields a series of important electrode kinetic transfer coefficients and exchange current densities for the elementary electrochemical reactions considered.