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

Electrochemical reduction of molecular O 2 to hydrogen peroxide (H 2 O 2 ) offers a promising solution for water purification and environmental remediation. Here, we design a hierarchical free‐standing single‐Co‐atom (with Co–N 4 coordination) electrode for oxygen reduction reaction (ORR) via a two‐electron pathway to make H 2 O 2 in acidic media. The current density of the single‐Co‐atom electrode reached 51 mA/cm 2 at 0.1 V vs reversible hydrogen electrode, lasting for more than 10 hours of continuous operation with H 2 O 2 selectivity greater than 80%. Toward practical application, the single‐Co‐atom electrode was directly used to assemble an electrochemical cell to produce H 2 O 2 at a rate of 676 mol/kg cat /h with a cell voltage of about 1.6 V.