High‐Valence‐Manganese Driven Strong Anchoring of Iridium Species for Robust Acidic Water Oxidation

Designing an efficient and durable electrocatalyst for the sluggish anodic oxygen evolution reaction (OER) has been the primary goal of using proton exchange membrane electrolyzer owing to the highly acidic and oxidative environment at the anode. In this work, it is reported that high-valence manganese drives the strong anchoring of the Ir species on the manganese dioxide (MnO2 ) matrix via the formation of an Mn-O-Ir coordination structure through a hydrothermal-redox reaction. The iridium (Ir)-atom-array array is firmly anchored on the Mn-O-Ir coordination structure, endowing the catalyst with excellent OER activity and stability in an acidic environment. Ir-MnO2 (160)-CC shows an ultralow overpotential of 181 mV at j = 10 mA cm-2 and maintains long-term stability of 180 h in acidic media with negligible decay, superior to most reported electrocatalysts. In contrast, when reacting with low-valence MnO2 , Ir species tend to aggregate into IrOx nanoparticles, leading to poor OER stability. Density functional theory (DFT) calculations further reveal that the formation of the Mn-O-Ir coordination structure can optimize the adsorption strength of *OOH intermediates, thus boosting the acidic OER activity and stability.