Confining High-Valence Iridium Single Sites onto Nickel\nOxyhydroxide for Robust Oxygen Evolution

Abstract

Enhancing\nactivity and stability of iridium- (Ir-) based oxygen\nevolution reaction (OER) catalysts is of great significance in practice.\nHere, we report a vacancy-rich nickel hydroxide stabilized Ir single-atom\ncatalyst (Ir₁–Ni­(OH)₂), which achieves\nlong-term OER stability over 260 h and much higher mass activity than\ncommercial IrO₂ in alkaline media. In situ X-ray absorption\nspectroscopy analysis certifies the obvious structure reconstruction\nof catalyst in OER. As a result, an active structure in which high-valence\nand peripheral oxygen ligands-rich Ir sites are confined onto the\nnickel oxyhydroxide surface is formed. In addition, the precise introduction\nof atomized Ir not only surmounts the large-range dissolution and\nagglomeration of Ir but also suppresses the dissolution of substrate\nin OER. Theoretical calculations further account for the activation\nof Ir single atoms and the promotion of oxygen generation by high-valence\nIr, and they reveal that the deprotonation process of adsorbed OH\nis rate-determining.