Progress in the Studies of Oxygen Reduction during the Last Thirty Years

Abstract

The oxygen reduction reaction, along with the hydrogen reaction, stands among the most important reactions in electrochemistry both from the practical/economical and theoretical point of view. Whereas meaningful kinetic and mechanistic studies of the hydrogen reaction can be traced back to the 1930s,(1) not much work had been done on the oxygen reduction reaction prior to 1960. At that time, kinetic-mechanistic studies in general, as opposed to those based on the equilibrium state and thermodynamics, were still, in a sense, in the embryonic stage. The first systematic analysis of the kinetics of the oxygen reduction appears to have been initiated around 1960 in Bockris’s laboratory at the University of Pennsylvania with the aim of determining the mechanisms of the reduction and to gain an insight into the catalysis and factors affecting the catalysis at different metals.(2–4) A program was set up at that time to study this reaction on noble metal electrodes and their alloys, specifically on Pt, Pd, and Rh, as well as on their alloys with Au.(4) In this early time, the accent was placed on Pt, and three major observations made regarding the kinetics of the reduction and the nature of the electrode surfaces proved to be keystones and provided the basis for much of the later and more detailed studies of this reaction, not only on Pt, but on other electrodes as well.