Atomically Dispersed Hexavalent Iridium Oxide from MnO Reduction for Oxygen Evolution Catalysis

Hexavalent iridium (Ir) oxide is predicted to be more active and stable than any other iridium oxide for the oxygen evolution reaction in acid; however, its experimental realization remains challenging. In this work, we report the synthesis, characterization, and application of atomically dispersed Ir oxide (Ir-) for proton exchange membrane (PEM) water electrolysis. The Ir- was synthesized by oxidatively substituting the ligands of potassium hexachloroiridate(IV) (KIrCl) with manganese oxide (MnO). The mass-specific activity (1.7 × 10 amperes per gram of iridium) and turnover number (1.5 × 10) exceeded those of benchmark iridium oxides, and in situ x-ray analysis during PEM operations manifested the durability of Ir at current densities up to 2.3 amperes per square centimeter. The high activity and stability of Ir- showcase its promise as an anode material for PEM electrolysis.