Electrocatalysts for O2 reduction

The proposed mechanisms for O2 reduction on various catalysts are discussed, taking into account the possible role of superoxide radicals, hydogen peroxide and adsorbed dioxygen. Particular attention is focused on O2 reduction on carbon and graphite (both with and without surface modifications), the anomalous temperature dependence of the Tafel slope for O2 reduction on Pt, transition metal macrocycles and heat treated macrocycles. The latter offer considerable promise as O2 reduction catalysts combining high activity with good stability.