Partial Exsolution Enables Superior Bifunctionality of Ir@SrIrO₃ for Acidic Overall Water Splitting

The pursuit of efficient and durable bifunctional electrocatalysts for overall water splitting in acidic media is highly desirable, albeit challenging. SrIrO₃ based perovskites are electrochemically active for oxygen evolution reaction (OER), however, their inert activities toward hydrogen evolution reaction (HER) severely restrict the practical implementation in overall water splitting. Herein, an Ir@SrIrO₃ heterojunction is newly developed by a partial exsolution approach, ensuring strong metal-support interaction for OER and HER. Notably, the Ir@SrIrO₃-175 electrocatalyst, prepared by annealing SrIrO₃ in 5% H₂ atmosphere at 175 °C, delivers ultralow overpotentials of 229 mV at 10 mA cm^-2 for OER and 28 mV at 10 mA cm^-2 for HER, surpassing most recently reported bifunctional electrocatalysts. Moreover, the water electrolyzer using the Ir@SrIrO₃-175 bifunctional electrocatalyst demonstrates the potential application prospect with high electrochemical performance and excellent durability in acidic environment. Theoretical calculations unveil that constructing Ir@SrIrO₃ heterojunction regulates interfacial electronic redistribution, ultimately enabling low energy barriers for both OER and HER.