In-situ formation of 3D vertical graphene by carbonizing organic precursor in ammonia

Abstract

Graphene edges, as opposed to the basal plane of graphene, present extremely high chemical reactivity due to their unique electronic state near the Fermi level, showing great promises for applications in electrochemical energy storage, electrocatalysis and contaminants adsorption. However, graphene edges are sparsely exposed due to the high aspect ratio and 2D nanosheet morphology of graphene materials. Herein, we report the surface graphenization of carbon with abundant exposed graphene edges by carbonizing organic polymer in ammonia. The formation of such unique structure is attributed to the preferable etching of ammonia on the flat (002) planes than the vertical ones. Resultantly, few-layered graphene with sharp edges is perpendicularly formed and fixed on the carbon surface without agglomeration. This unique edge structure contributes to a high specific surface area of 2150 m2 g−1 with a large pore volume of 1.5 cm3 g−1 of carbon, exceeding most of commercially available activated carbons but avoiding the use of the awkward KOH. The high surface area of carbon, together with highly reactive graphene edges, provides numerous sites for ion storage and adsorption. It exhibits a high energy density of 68.16 Wh kg−1 in ionic liquid-based symmetric supercapacitor and presents superior adsorption capabilities toward various organic contaminants including dyes, organic solvents and oils, especially methylene blue (961.3 mg g−1). Our finding proves the feasibility of surface graphenization of carbon and provides a new way to enhance the surface reactivity of functional carbon materials.