Design of hierarchical, three‐dimensional free‐standing single‐atom electrode for H₂O₂ production in acidic media

Abstract Electrochemical reduction of molecular O₂ to hydrogen peroxide (H₂O₂) offers a promising solution for water purification and environmental remediation. Here, we design a hierarchical free‐standing single‐Co‐atom (with Co–N₄ coordination) electrode for oxygen reduction reaction (ORR) via a two‐electron pathway to make H₂O₂ in acidic media. The current density of the single‐Co‐atom electrode reached 51 mA/cm² at 0.1 V vs reversible hydrogen electrode, lasting for more than 10 hours of continuous operation with H₂O₂ selectivity greater than 80%. Toward practical application, the single‐Co‐atom electrode was directly used to assemble an electrochemical cell to produce H₂O₂ at a rate of 676 mol/kg_cat/h with a cell voltage of about 1.6 V.