Boron-driven edge loop formation in reduced graphene oxide enhances oxidative stability and electrical conductivity

Abstract

Boron-doped reduced graphene oxides (B-rGO) were prepared by thermally treating GO with boric acid in argon at temperatures above 1300°C. Oxidized boron species formed at low temperatures progressively converted into substitutional BC₃ above 1500°C, where they were incorporated into the sp² lattice. Boron also promoted the formation of closed-loop edge structures, thereby stabilizing high-energy open sites. Although substitutional boron atoms were incorporated into the sp² framework, they induced localized distortions in both the lattice symmetry and the electronic environment. Accordingly, Raman spectra showed an intense D band and a suppressed G’ band, while XPS analysis revealed a reduced sp²/sp³ ratio, collectively indicating that boron functions as a defect in both optical and electronic terms. These BC₃ dopants, particularly at looped edges, covalently linked graphene layers, increasing both the oxidation onset temperature and domain conductivity. Although edge looping increased interparticle resistance to some extent, B-rGO samples still exhibited higher overall conductivity than undoped rGO. Theoretical simulations further supported the mechanism, showing that substitutional boron at armchair edges enhanced peroxide ion adsorption through electron transfer. In contrast, looped-edge configurations exhibited weak peroxide binding, suggesting improved oxidation resistance through the reduced edge-reactivity. Taken together, these results reveal a direct link between boron doping, edge stabilization, and functional enhancement, and provide a strategy for designing high-performance carbon materials for energy and environmental applications.