Abstract
Identifying and tailoring active sulfur configurations in heteroatom-doped carbon electrocatalysts for the selective 2e(-) oxygen reduction reaction (ORR) pathway remains a significant challenge. Here we designed and synthesized sulfur-doped reduced graphene oxide electrocatalysts containing C-S and C-SO (x) moieties (denoted as S (x) RGO, x = 1, 10, 20) for promising ORR into hydrogen peroxide (H(2)O(2)). The optimized S(10)RGO catalyst exhibits unexpected H(2)O(2) selectivity of ca. 90% across a wide voltage range of 0.10-0.65 V, accompanied with excellent long-term stability (40 h) in an alkaline flow cell with 90.5% H(2)O(2) faradaic efficiency at an industrial current density of 300 mA cm(-2). Theoretical and experimental analyses integrally reveal and identify the C-S and C-SO (x) groups as the main active sites in the carbon-based catalyst. Specifically, the C-S group is found to favor the formation of OOH*, while the C-SO (x) group not only facilitates the desorption of OOH* but also modulates interfacial mass transport kinetics, thereby creating a favorable microenvironment for H(2)O(2) generation.