Abstract
The electrocatalytic oxygen reduction reaction (ORR) lies at the heart of low-temperature proton exchange membrane fuel cells. Despite its apparent simplicity, to understand the mechanism of the ORR and overcome the significant overpotential associated with it has occupied the attention of researchers worldwide in recent years, with some important questions remaining open. This chapter reviews some of the recent developments in ORR research. In particular, we discuss the recent findings on the adsorptions of oxygenated species and specific anions and their implications for the ORR; the coverage- and potential-dependent nature of the ORR mechanism on Pt; the synergistic interplay between experiment and theory that has led to the development of a novel class of mixed Pt monolayer catalysts, which possess markedly higher ORR activity than
commercial Pt catalysts; and the factors that affect the stability of the Pt catalysts and a novel method that we have recently identified which stabilizes the Pt catalysts by modifying them with Au.