Single-atom Iron Catalyst with Biomimetic Active Center to Accelerate Proton Spillover for Medical-level Electrosynthesis of H₂ O₂ Disinfectant

Electrosynthesis of H₂ O₂ has great potential for directly converting O₂ into disinfectant, yet it is still a big challenge to develop effective electrocatalysts for medical-level H₂ O₂ production. Herein, we report the design and fabrication of electrocatalysts with biomimetic active centers, consisting of single atomic iron asymmetrically coordinated with both nitrogen and sulfur, dispersed on hierarchically porous carbon (Fe_SA -NS/C). The newly-developed Fe_SA -NS/C catalyst exhibited a high catalytic activity and selectivity for oxygen reduction to produce H₂ O₂ at a high current of 100 mA cm^-2 with a record high H₂ O₂ selectivity of 90 %. An accumulated H₂ O₂ concentration of 5.8 wt.% is obtained for the electrocatalysis process, which is sufficient for medical disinfection. Combined theoretical calculations and experimental characterizations verified the rationally-designed catalytic active center with the atomic Fe site stabilized by three-coordinated nitrogen atoms and one-sulfur atom (Fe-N₃ S-C). It was further found that the replacement of one N atom with S atom in the classical Fe-N₄ -C active center could induce an asymmetric charge distribution over N atoms surrounding the Fe reactive center to accelerate proton spillover for a rapid formation of the OOH* intermediate, thus speeding up the whole reaction kinetics of oxygen reduction for H₂ O₂ electrosynthesis.