Sub-5 nm amorphous iridium oxide nanosheets with synergistic multi-element doping for enhanced acidic oxygen evolution electrocatalysis
Abstract
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 (IrOx)-based catalysts and the scarcity of iridium. Herein, we introduce a novel strategy to synthesize ultra-thin amorphous IrOx nanosheets with flexible mono/multi-element doping. Benefiting from synergistic W/Mo/Co co-doping effect, WMoCo-IrOx nanosheets (WMC-IrOx 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-IrOx 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-IrOx 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 O2 release, thereby lowering OER energy barriers in acidic conditions. This work opens an inspiring avenue for designing IrOx-based catalysts with high activity and low Ir usage.