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 (IrSAE) stabilized on the surface of Mn-substituted spinel Co3O4 (IrSAE-CMO), which exhibits excellent mass activity and significantly improved durability (degradation-rate: ≈2mVh-1), outperforming benchmark IrO2 (≈44mVh-1) and conventional Irsingle-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 Irsingle-atoms on the CMO surface compared to pristine-Co3O4, facilitating the migration of Irsingle-atoms to form strongly correlated IrSAE during pyrolysis. Extensive ex situ characterization, operando X-ray absorption and Raman spectroscopies, pH-dependence activity tests, and theoretical calculations indicate that the rigid IrSAE 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.