Oxygen reduction reaction by noble metal-based catalysts

Oxygen reduction reaction (ORR) is a key component for various biochemical processes, aerobic oxidation, and energy related applications. Oxygen reduction is a complex multi-electron multi-proton reaction and is often complicated because of the selectivity issue. While complete reduction of oxygen affords water, its partial reduction to hydrogen peroxide is also feasible. Oxygen reduction to water is thermodynamically favorable and there is an ongoing effort to use this reaction as a cathodic half-cell in fuel cell. Oxygen reduction to either water or hydrogen peroxide is also important in carrying out aerobic oxidation reactions of organic molecules. Catalysts made of noble metals are known to be the best performer for the ORR, but the scarcity and high price of these catalysts encourage the researchers to search for methodologies for minimizing the catalyst loading without compromising the activity. This chapter deals with such strategies highlighting the role of noble metal-based catalysts in oxygen reduction reaction relevant to energy related and aerobic oxidation reactions.