Scalable synthesis of an IrO_x/Ir-Co₃O₄ heterostructure for efficient and stable acidic oxygen evolution

The deployment of proton exchange membrane water electrolysis (PEMWE) necessitates efficient, stable, and low-Ir electrocatalysts for acidic oxygen evolution reaction (OER) at the anode. Herein, an IrO_x/Ir-Co₃O₄ heterostructure electrocatalyst is developed featuring bulk-doped Ir-Co₃O₄ with surface-anchored IrO_x, synthesized via a facile two-step electrochemical co-deposition process followed by programmed annealing. The IrO_x/Ir-Co₃O₄ catalyst requires an overpotential of only 237 mV to reach 10 mA/cm² and achieves a high mass activity of 230 A/g_Ir at 1.5 V versus RHE. In a 1 cm² membrane electrode assembly electrolyzer (Pt/C∥IrO_x/Ir-Co₃O₄), a cell voltage of only 1.773 V delivers 1 A/cm², with stable operation exceeding 160 h at 200 mA/cm². Moreover, a 100 cm² IrO_x/Ir-Co₃O₄ anode was fabricated, exhibiting performance comparable to that of its 1 cm² counterpart. Structural and computational analyses reveal that the synergy between bulk-doped Ir-Co₃O₄ and surface anchored IrO_x optimizes the electronic structure, thereby enhancing both catalytic activity and durability. This work provides a viable and scalable pathway for developing low-Ir electrocatalysts for practical PEMWE applications.