Metal-free sulfur-doped reduced graphene oxide electrocatalysts for promising production of hydrogen peroxide: construction and identification of active sites.

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 moieties (denoted as S RGO, = 1, 10, 20) for promising ORR into hydrogen peroxide (HO). The optimized SRGO catalyst exhibits unexpected HO selectivity of 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% HO faradaic efficiency at an industrial current density of 300 mA cm. Theoretical and experimental analyses integrally reveal and identify the C-S and C-SO 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 group not only facilitates the desorption of OOH* but also modulates interfacial mass transport kinetics, thereby creating a favorable microenvironment for HO generation.