Single-atom-engineered perovskite enables near-theoretical-rate hydroxyl radical electrogeneration

Electrochemical advanced oxidation that directly activates O₂ through the oxygen reduction reaction (ORR) to generate hydroxyl radicals (•OH) offers a sustainable strategy for degrading persistent organic pollutants. However, prevailing approaches typically rely on a stepwise process involving the 2e⁻ ORR to produce H₂O₂ followed by 1e⁻ activation. High barriers associated with intermediate desorption and inter-site transfer consequently limit the •OH yield. Here, we construct a single-active-site architecture in the perovskite oxide Pr_1.0Sr_1.0Fe_0.5Zn_0.25Mo_0.25O_4-δ (PSFZM) that enables a direct three-electron ORR pathway for efficient •OH generation. The Zn^δ⁺ single active center selectively stabilizes *OOH and *H₂O₂ through weak orbital interactions, while an adjacent Mo atom polarizes the O atoms of adsorbed H₂O₂, promoting cleavage of the peroxide bond at the active site. This strategy avoids intermediate desorption and migration, enabling continuous proton-coupled electron transfer. The catalyst achieves a •OH production rate of 821 μmol h⁻¹ and an O₂ utilization of 37.7%, metrics competitive with previously reported systems. In a membrane-free flow cell that uses gaseous O₂ directly, the •OH generation efficiency reaches 64.7%. By combining atomic-level catalyst design with reactor engineering, this work establishes a scalable platform for sustainable wastewater treatment.