Supported IrO₂ Nanocatalyst with Multilayered Structure for Proton Exchange Membrane Water Electrolysis

Abstract The design of a low‐iridium‐loading anode catalyst layer with high activity and durability is a key challenge for a proton exchange membrane water electrolyzer (PEMWE). Here, the synthesis of a novel supported IrO₂ nanocatalyst with a tri‐layered structure, dubbed IrO₂@TaO_x@TaB that is composed of ultrasmall IrO₂ nanoparticles anchored on amorphous TaO_x overlayer of TaB nanorods is reported. The composite electrocatalyst shows great activity and stability toward the oxygen evolution reaction (OER) in acid, thanks to its dual‐interface structural feature. The electronic interaction in IrO₂/TaO_x interface can regulate the coverage of surface hydroxyl groups, the Ir³⁺/ Ir⁴⁺ ratio, and the redox peak potential of IrO₂ for enhancing OER activity, while the dense TaO_x overlayer can prevent further oxidation of TaB substrate and stabilize the IrO₂ catalytic layers for improving structural stability during OER. The IrO₂@TaO_x@TaB can be used to fabricate an anode catalyst layer of PEMWE with an iridium‐loading as low as 0.26 mg cm⁻². The low‐iridium‐loading PEMWE delivers high current densities at low cell voltages (e.g., 3.9 A cm⁻²@2.0 V), and gives excellent activity retention for more than 1500 h at 2.0 A cm⁻² current density.