Iridium single atoms coupling with oxygen vacancies boosts oxygen evolution reaction in acid media

Simultaneous realization of improved activity, enhanced stability, and reduced cost remains a desirable yet challenging goal in the search of electrocatalysis oxygen evolution reaction (OER) in acid. Herein, we report a novel strategy to prepare iridium single-atoms (Ir-SAs) on ultrathin NiCo₂O₄ porous nanosheets (Ir-NiCo₂O₄ NSs) by the co-electrodeposition method. The surface-exposed Ir-SAs couplings with oxygen vacancies (V_O) exhibit boosting the catalysts OER activity and stability in acid media. They display superior OER performance with an ultralow overpotential of 240 mV at j = 10 mA cm^-2 and long-term stability of 70 h in acid media. The TOFs of 1.13 and 6.70 s^-1 at an overpotential of 300 and 370 mV also confirm their remarkable performance. Density functional theory (DFT) calculations reveal that the prominent OER performance arises from the surface electronic exchange-andtransfer activities contributed by atomic Ir incorporation on the intrinsic V_O existed NiCo₂O₄ surface. The atomic Ir sites substantially elevate the electronic activity of surface lower coordinated Co sites nearby V_O, which facilitate the surface electronic exchange-and-transfer capabilities. With this trend, the preferred H₂O activation and stabilized ^∗O have been reached toward competitively lower overpotential. This is a generalized key for optimally boosting OER performance. © 2020 American Chemical Society.