Direct anodic exfoliation of graphite onto high-density aligned graphene for large capacity supercapacitors

Abstract

Vertically oriented graphene nanosheets (VOGNs) fabricated on conductive substrates with a large amount of edge planes and open channels are ideal for electrochemical double-layer (EDL) capacitor electrodes. However, preparation of such a structure with high-density of graphene nanosheets is challenging. Herein, a facile, environment-friendly, and economical technique to prepare high-quality VOGNs directly on conductive graphite plates with a high mass loading is described. The VOGNs are obtained by electrochemical anodization of graphite and a large amount of aligned reduced graphene oxide (rGO) is produced and adheres strongly to the graphite substrate (G@rGO). The symmetrical supercapacitors composed of the G@rGO electrodes exhibit a high volumetric capacitance of 3.9Fcm−3 and energy density of 0.66WhL−1 (based on the volume of the whole electrode) at a current density of 7.5mAcm−3 in 6M KOH. The rate performance and long-term cycling stability are very good. The outstanding capacitive performance can be attributed to the unique structure of the G@rGO electrode which facilitates transportation of ions between the electrolyte and graphene surface, minimizes the distributive nature of charge storage, expedites the formation of EDL, and enhances the electrochemical utilization of graphene and stability by avoiding restacking and aggregation of graphene nanosheets.