Synergistic Co─Ir/Ru Composite Electrocatalysts Impart Efficient and Durable Oxygen Evolution Catalysis in Acid

Abstract Exploring highly active and robust catalysts, which have low precious metal content, to boost the kinetically sluggish oxygen evolution reaction (OER) is a key concern for hydrogen production via proton exchange membrane water electrolysis (PEMWE). Here, rational engineering of the morphology and the local geometric ligand environment of Ir and Ru catalysts are presented by using defect‐rich, lanthanum‐ and lithium‐doped Co 3 O 4 nanofiber (LLCF) as substrate that promotes the electrocatalytic OER. Two catalysts, IrCoOx@LLCF and RuCoOx@LLCF, achieve mass activities of 1013.5 A g Ir −1 and 1911.4 A g Ru −1 in 0.1 m HClO 4 at 300 mV overpotential, respectively, which are 26 and 50 times higher than that of commercial IrO 2 and RuO 2 . Operando X‐ray absorption spectroscopy unveils the reversible structure of IrCoOx during the OER and the suppression of over‐oxidation of Co and Ir, giving rise to high stability. Density functional theory calculations reveal that the local geometric ligand engineering optimizes the binding of oxygenated species to the active sites, resulting in strongly enhanced catalytic activity.