Deciphering Interfacial Electronic Interactions Between Iridium Oxide and Ni-Based Supports for High-Current-Density...

Enhancing the oxygen evolution reaction (OER) performance of Ir-based catalysts while minimizing Ir usage is crucial for advancing anion exchange membrane water electrolyzers (AEMWEs). Herein, we present binder-free iridium oxide (IrO₂)-Ni-based electrodes prepared via a liquid-phase synthesis, which directly anchors an ultralow quantity of IrO₂ nanoparticles onto versatile Ni-based foams. This design enables systematic investigation of how Ni-based support chemistry modulates interfacial electronic interactions and thereby dictates catalytic performance. Electrochemical measurements reveal that IrO₂ on nickel phosphide (Ni₂P) exhibits the highest activity and durability, with a significantly low overpotential of 232 mV and stable operation over 400 h at 10 mA cm^-2. Spectroscopic and density functional theory (DFT) analyses reveal that strong interfacial charge transfer between IrO₂ and Ni₂P enriches the electron density around Ir and downshifts the Ir d-band center, thereby optimizing the adsorption energetics of OER intermediates and accelerating the reaction kinetics. The binder-free configuration enhances mechanical integrity and mass transport, which enables high-current-density operation (3.1 A cm^-2 at 2.0 V_cell) under practical AEMWE conditions. Thus, the Ni-based support material enables tuning of the interfacial electronic coupling and catalytic behavior of IrO₂, thereby supporting the development of binder-free low Ir-loaded electrodes for cost-effective and durable AEMWEs.