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 (H2O2) 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 H2O2 in acidic media. The current density of the single-Co-atom electrode reached 51mA/cm(2) at 0.1V vs reversible hydrogen electrode, lasting for more than 10hours 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 676mol/kg(cat)/h with a cell voltage of about 1.6V.