Highly Selective Hydrogen Peroxide Electrosynthesis on Carbon: In Situ Interface Engineering with Surfactants

In situ modulation of surface reaction is a powerful approach to drive high-yield H2O2 electrosynthesis on metal-free carbon. Here, we discover that cationic surfactants can work efficiently as an in situ kinetic promoter for the oxygen-to-peroxide reaction on a carbon black electrode, achieving a peroxide yield above 90% (up to 95.2%) across a >0.8 V window in alkaline media, the best among reported H2O2 electrocatalysts. Our characterizations and kinetic model analysis show that the high peroxide selectivity is attributable to surface carboxylates (–COO−) with weak peroxide binding under a Coulombic pull imposed by an adsorbed cationic layer. Although surface carbonyls (–C=O) also participate in the peroxide synthesis, they exhibit strong binding to peroxide and promote on-site reduction at moderate-to-high overpotential. At only a minute amount of cationic surfactant, a chronoamperometry experiment with a carbonyl-free system can deliver a peroxide production at a sustainably high selectivity (∼96%) over 10 h.