Sub-5 nm amorphous iridium oxide nanosheets with synergistic multi-element doping for enhanced acidic oxygen evolution electrocatalysis

Acidic oxygen evolution reaction (OER) is crucial for developing proton exchange membrane water electrolyzers, which has been hindered by the high overpotential of iridium oxide (IrO x )-based catalysts and the scarcity of iridium. Herein, we introduce a novel strategy to synthesize ultra-thin amorphous IrO x nanosheets with flexible mono/multi-element doping. Benefiting from synergistic W/Mo/Co co-doping effect, WMoCo-IrO x nanosheets (WMC-IrO x NS) sample optimally modulates the Ir electronic structure, maintains the neutral oxygen vacancy concentration and stabilizes Ir sites. Additionally, the nanosheets expose abundant Ir active centers. WMC-IrO x NS exhibits superior OER electrocatalysis performance with a low overpotential of 241 mV, excellent stability of 275 h at 10 mA cm −2 , and a high mass activity of 545.4 A/g Ir. The catalyst follows the lattice oxygen mechanism (LOM) pathway. As observed in in situ attenuated total reflectance Fourier transform infrared spectroscopy, compared to the un-doped sample, WMC-IrO x NS accumulates negligible Ir–O–O* intermediates. Therefore, through the multi-element synergistic co-doping effect, the catalyst weakens the adsorption energy of O–O* intermediates and promotes O 2 release, thereby lowering OER energy barriers in acidic conditions. This work opens an inspiring avenue for designing IrO x -based catalysts with high activity and low Ir usage.