Ultrasmall IrO₂ nanoparticles anchored on hollow Co-Mo multi-oxide heterostructure nanocages for efficient oxygen evolution in acid

The application of proton exchange membrane water electrolysis (PEMWE) is largely limited by the sluggish oxygen evolution reaction (OER) kinetics, which usually requires noble metal Ir/Ru-based catalysts. It's desirable to design low-cost catalysts with less content of Ir/Ru in OER without sacrificing their catalytic performance. Herein, the ultrasmall IrO2 nanoparticles uniformly dispersed on Co3O4-CoMoO4 nanocages (IrO2@Co3O4- CoMoO4) electrocatalyst is demonstrated. Structural characterization indicates that hollow Co3O4-CoMoO4 acts as the effective support to provide abundant anchoring sites and heterogenous interfaces, which enable the catalyst to expose more active sites and accelerate charge transport. As a result, the representative IrO2@Co3O4- CoMoO4 exhibits an outstanding OER activity (eta = 236 mV at 10 mA cm-2) with a superior mass activity of 713 A g-1 Ir at 1.53 V vs. RHE in 0.5 M H2SO4 that are comparable to most reported catalysts. Theoretical calculations also reveal that the introduction of Mo can effectively modify electronic structure and decrease adsorption en-ergy barriers of oxygen intermediates, and thereby enhancing OER catalytic activity. This work provides a new idea to develop highly efficient low Ir catalysts for OER.