Spinel-Anchored Iridium Single Atoms Enable Efficient Acidic Water Oxidation via Intermediate Stabilization Effect

Iridium oxide is considered the only practical catalyst for oxygen evolution reaction (OER) in commercial proton exchange membrane (PEM) electrolyzers. However, its low activity and high cost greatly hinder the large-scale development of PEM electrolyzers for hydrogen production. Herein, we report atomically dispersed Ir atoms incorporated into a spinel Co3O4lattice as an acidic OER catalyst, which exhibits excellent activity and stability for water oxidation. The catalyst significantly lowers the over-potential down to 226 mV at 10 mA cm-2 with an ultrahigh turnover frequency value of 3.15 s-1 (eta = 300 mV), 3 orders of magnitude higher than that of commercial IrO2. Meanwhile, the catalyst shows superior corrosion resistance in an acidic OER condition, reaching a lifespan of up to 500 h at 10 mA cm-2. First-principles calculations reveal that the key *OOH intermediate can be stabilized by the lattice oxygen coordinated to the Ir active site via hydrogen bond formation, which substantially regulates the rate-limiting step and lowers the activation free energy of the OER process. This work demonstrates a strategy for improving the OER activity of Ir-based catalysts and provides insights into the regulation of the reaction mechanism.