Atomically dispersed chromium coordinated with hydroxyl clusters enabling efficient hydrogen oxidation on ruthenium

Overcoming the sluggish kinetics of alkaline hydrogen oxidation reaction (HOR) is challenging but is of critical importance for practical anion exchange membrane fuel cells. Herein, abundant and efficient interfacial active sites are created on ruthenium (Ru) nanoparticles by anchoring atomically isolated chromium coordinated with hydroxyl clusters (Cr 1 (OH) x ) for accelerated alkaline HOR. This catalyst system delivers 50-fold enhanced HOR activity with excellent durability and CO anti-poisoning ability via switching the active sites from Ru surface to Cr 1 (OH) x -Ru interface. Fundamentally different from the conventional mechanism merely focusing on surface metal sites, the isolated Cr 1 (OH) x could provide unique oxygen species for accelerating hydrogen or CO spillover from Ru to Cr 1 (OH) x . Furthermore, the original oxygen species from Cr 1 (OH) x are confirmed to participate in hydrogen oxidation and H 2 O formation. The incorporation of such atomically isolated metal hydroxide clusters in heterostructured catalysts opens up new opportunities for rationally designing advanced electrocatalysts for HOR and other complex electrochemical reactions. This work also highlights the importance of size effect of co-catalysts, which should also be paid substantial attention to in the catalysis field.