In-Plane Topological-Defect-Enriched Graphene as an Efficient Metal-Free Catalyst for pH-Universal H2 O2 Electrosynthesis

Abstract

Developing efficient metal-free catalysts to directly synthesize hydrogen peroxide (H₂ O₂ ) through a 2-electron (2e) oxygen reduction reaction (ORR) is crucial for substituting the traditional energy-intensive anthraquinone process. Here, in-plane topological defects enriched graphene with pentagon-S and pyrrolic-N coordination (SNC) is synthesized via the process of hydrothermal and nitridation. In SNC, pentagon-S and pyrrolic-N originating from thiourea precursor are covalently grafted onto the basal plane of the graphene framework, building unsymmetrical dumbbell-like S─C─N motifs, which effectively modulates atomic and electronic structures of graphene. The SNC catalyst delivers ultrahigh H₂ O₂ productivity of 8.1, 7.3, and 3.9 mol g_catalyst ^-1 h^-1 in alkaline, neutral, and acidic electrolytes, respectively, together with long-term operational stability in pH-universal electrolytes, outperforming most reported carbon catalysts. Theoretical calculations further unveil that defective S─C─N motifs efficiently optimize the binding strength to OOH^* intermediate and substantially diminish the kinetic barrier for reducing O₂ to H₂ O₂ , thereby promoting the intrinsic activity of 2e-ORR.

Keywords: electrosynthesis; graphene; hydrogen peroxide (H2O2); metal-free catalyst; topological defect.