LAUSR

Summary Achieving high activity and long-term stability is a major challenge in the design of catalysts. In particular, the oxygen evolution reaction (OER) in acidic media, which plays a key role in proton exchange membrane electrolyzers for fast hydrogen fuel generation, seriously suffers from rapid degradation of catalysts as a result of the harsh acidic and oxidative conditions. Here, we report a rational design strategy for the fabrication of a heterostructured OER electrocatalyst (Ru@IrOx) that has unique physicochemical properties and in which a strong charge redistribution exists between a highly strained ruthenium core and a partially oxidized iridium shell across the metal-metal oxide heterojunction. The increased valence of the iridium shell and the decreased valence of the ruthenium core activate a synergistic electronic and structural interaction, which results in the enhanced activity and stability of the catalyst compared with the majority of the state-of-the-art ruthenium- and iridium-based materials.