High-valence Ir single atoms enhance oxygen evolution electrocatalysis

High-valent metal single atoms generally exhibit exceptional electrocatalytic activity because of their rapid electron-transfer kinetics. However, their synthesis remains a formidable challenge owing to intrinsic instability under typical preparation conditions. Herein, atomically dispersed Ir³⁺ single atoms were successfully stabilized on a NiS₂ matrix via a substitutional replacement of Ni lattice sites by Ir, followed by coordination with adjacent S atoms. The resulting catalyst delivers outstanding oxygen evolution reaction (OER) performance, achieving a current density of 10 mA cm^-2 at an overpotential of only 190 mV. Density-functional theory (DFT) calculations reveal that the high oxidation state of Ir upshifts the Ni d-band center toward the Fermi level, thereby strengthening OOH* adsorption and accelerating the OER kinetics. This work not only provides a robust strategy for constructing high-valent single-atom catalysts but also highlights the pivotal role of sulfide supports in stabilizing high oxidation states for advanced electrocatalysis.