Benzoxazole and benzimidazole heterocycle-grafted graphene for high-performance supercapacitor electrodes

Abstract

An efficient method for the preparation of benzoxazole and benzimidazole covalently grafted graphene and their application as high performance electrode materials for supercapacitors is reported. The synthesis of such covalently functionalized graphene materials first involves a cyclization reaction of carboxylic groups on graphene oxide with the hydroxyl and aminos groups on o-aminophenol and o-phenylenediamine, and subsequent reduction by hydrazine. Results of Fourier transformed infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and thermogravimetric analysis (TGA) have confirmed that the covalent functionalization of graphene is achieved through the formation of benzoxazole and benzimidazole on the graphene sheets. The functionalized graphene materials are revealed to consist of corrugation and scrolling morphologies with less aggregation, indicating the effectiveness of functionalization in preventing restacking/aggregation of the graphene sheets. Furthermore, when applied as supercapacitor electrodes, the functionalized graphene materials exhibit good electrochemical performances in terms of high specific capacitance (730 and 781 F g⁻¹ for benzoxazole and benzimidazole grafted graphene, respectively, at a current density of 0.1 A g⁻¹) and good cycling stability, implying their potential for energy storage applications.