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

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.