Integrating Atomically Dispersed Ir Sites in MnCo2O4.5 for Highly Stable Acidic Oxygen Evolution Reaction

Industrial water electrolysis requires oxygen evolution reaction (OER) catalysts that exhibit both high activity and adaptability to high current densities. However, single Ir atoms of the OER catalysts often show high performance in the three-electrode system but are limited to low current densities in proton exchange membrane water electrolyzers (PEMWE). The high oxidation potential and catalyst shedding caused by oxygen bubble desorption have hindered the stability, resulting in unsatisfactory PEMWE performance. Achieving high catalytic stability under high current density conditions still presents a significant challenge for all of the OER catalysts. In this study, an efficient and stable catalytic system for OER is constructed by a doping strategy, which consists of atomically dispersed Ir sites in MnCo2O4.5. The integrated Ir–MnCo2O4.5 catalyst demonstrates remarkable OER activity, with a low overpotential of 238 mV at 10 mA/cm2. It exhibits long-term stability, maintaining this high activity for 700 h at 20 mA/cm2 with a degradation rate of 0.025 mV/h. Impressively, the PEMWE with the integrated Ir–MnCo2O4.5 as the anode remains stable even after nearly 100 h at 200 mA/cm2, outperforming most previously reported single-iridium atom-based PEMWEs. Density functional theory calculations show that the redistribution of charges brought by the introduction of Ir and Mn not only effectively reduces the dissolution of lattice oxygen and Ir active sites but also lowers the energy barrier of the rate-determining step, thereby significantly improving the stability and activity of Ir–MnCo2O4.5 under high current density.