Mesoporous Single-Crystalline Particles as Robust and Efficient Acidic Oxygen Evolution Catalysts

The scarcity of iridium (Ir) limits its widespread use in acidic oxygen evolution reaction (OER). Herein, mesoporous single-crystalline spinel Co₃O₄ with atomically dispersed low-valence-state Ir has been developed to enable Ir's efficient and stable utilization. The surface Pourbaix diagram suggests that under acidic OER conditions, O* fully covers both Co₃O₄(111) and (110) surfaces, passivating Co sites but enhancing Co₃O₄'s structural stability, a benefit further improved by Ir doping. Mesopores offer numerous loading sites for Ir single atoms (13.8 wt %), which activate the originally O*-passivated Co₃O₄(111) surface by creating high-intrinsic-activity Co-Ir bridge sites; meanwhile, Ir and Co leaching rates are reduced to about 1/4 and 1/5, respectively, compared to conventional Ir/Co₃O₄ catalysts. Our catalyst exhibits a low η₁₀ of 248 mV for over 100 h, showcasing its potential in water electrolysis.