Chemical Ex‐Solution of Bi 3‐x TaO 7 Support for Electrical Integration at the Interface With Ir─Bi Alloy Electrocatalysts in Acidic Oxygen Evolution Reaction

Reducing iridium (Ir) loading while maintaining high activity and durability remains a critical challenge for proton exchange membrane water electrolysis. While oxide‐supported catalysts offer a pathway for Ir reduction, their intrinsic low electronic conductivity and inefficient charge transfer at catalyst‐support interfaces remain imperative bottlenecks. Herein, we report a synergistic interfacial engineering strategy of catalyst‐support based on partial ex‐solution of Bi from a Bi 3 TaO 7 support. Ex‐solved Bi forms highly active Ir─Bi alloy domains while generating a Bi‐deficient support and markedly improving the conductivity of the support. Moreover, this coupled reconstruction lowers the work function of the Ir‐based catalyst while increasing the work function of the support, shifting the catalyst‐support contact from rectifying to ohmic, thereby facilitating efficient electron transport. The resulting IrBi/Bi 3‐x TaO 7 exhibits enhanced half‐cell oxygen evolution reaction activity (248 mV at 10 mA/cm 2 ), mass activity (1077 mA/mg Ir at 1.55 V), and durability (15.8 h). Furthermore, single‐cell measurements achieve outstanding performance of 1.824 V at 2 A/cm 2 with a low Ir loading of 0.38 mg/cm 2 and negligible voltage degradation over 100 h. This work highlights a generalizable strategy for simultaneous electronic integration of catalyst and support, offering new insights into the design of efficient and durable electrocatalysts for PEMWE.