Ir-Sn pair-site triggers key oxygen radical intermediate for efficient acidic water oxidation.

The anode corrosion induced by the harsh acidic and oxidative environment greatly restricts the lifespan of catalysts. Here, we propose an antioxidation strategy to mitigate Ir dissolution by triggering strong electronic interaction via elaborately constructing a heterostructured Ir-Sn pair-site catalyst. The formation of Ir-Sn dual-site at the heterointerface and the resulting strong electronic interactions considerably reduce d -band holes of Ir species during both the synthesis and the oxygen evolution reaction processes and suppress their overoxidation, enabling the catalyst with substantially boosted corrosion resistance. Consequently, the optimized catalyst exhibits a high mass activity of 4.4 A mg Ir -1 at an overpotential of 320 mV and outstanding long-term stability. A proton-exchange-membrane water electrolyzer using this catalyst delivers a current density of 2 A cm -2 at 1.711 V and low degradation in an accelerated aging test. Theoretical calculations unravel that the oxygen radicals induced by the π* interaction between Ir 5 d -O 2 p might be responsible for the boosted activity and durability.