Iridium Single-Atom-Ensembles Stabilized on Mn-Substituted Spinel Oxide for Durable Acidic Water Electrolysis

Exploring single-atom-catalysts for the acidic oxygen evolution reaction (OER) is of paramount importance for cost-effective hydrogen production via acidic water electrolyzers. However, the limited durability of most single-atom-catalysts and Ir/Ru-based oxides under harsh acidic OER conditions, primarily attributed to excessive lattice oxygen participation resulting in metal-leaching and structural collapse, hinders their practical application. Herein, an innovative strategy is developed to fabricate short-range Ir single-atom-ensembles (Ir_SAE) stabilized on the surface of Mn-substituted spinel Co₃O₄ (Ir_SAE-CMO), which exhibits excellent mass activity and significantly improved durability (degradation-rate: ≈2 mV h^-1), outperforming benchmark IrO₂ (≈44 mV h^-1) and conventional Ir_single-atoms on pristine-Co₃O₄ for acidic OER. First-principle calculations reveal that Mn-substitution in the octahedral sites of Co₃O₄ substantially reduces the migration energy barrier for Ir_single-atoms on the CMO surface compared to pristine-Co₃O₄, facilitating the migration of Ir_single-atoms to form strongly correlated Ir_SAE during pyrolysis. Extensive ex situ characterization, operando X-ray absorption and Raman spectroscopies, pH-dependence activity tests, and theoretical calculations indicate that the rigid Ir_SAE with appropriate Ir-Ir distance stabilized on the CMO surface effectively suppresses lattice oxygen participation while promoting direct O─O radical coupling, thereby mitigating Ir-dissolution and structural collapse, boosting the stability in an acidic environment.