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

Abstract 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.