Oxide Electrocatalysts Based on Earth-Abundant Metals for Both Hydrogen- and Oxygen-Evolution Reactions

A unique bifunctional oxide electrocatalyst capable of catalyzing both half-reactions of water splitting, namely, oxygen-evolution reaction (OER) and hydrogen-evolution reaction (HER), with the added capability of catalyzing HER in both acidic and basic media, a rare property in water-splitting catalysts, is reported. In addition to the bifunctional electrocatalytic properties, CaSrFeMnO6-delta shows OER activity, which is even superior to the reported activities of precious-metal electrocatalysts, IrO2 and RuO2. The correlation of electrocatalysis with the charge-transport properties in the series Ca2FeMnO6-delta, CaSrFeMnO6-delta, and Sr2FeMnO6-delta is demonstrated. Given the dependence of charge transport on structure and defects, this work unravels the interesting correlations between the triangle of structure, charge transport, and electrocatalytic activity for water splitting.