Preparation and capacitance performance of few-layer graphene

Abstract

ABSTRACT The well-controlled graphene was prepared by pre-oxidisation, full-oxidisation and hydrothermal reduction of flake graphite. The graphene oxide (GO) reveals the overlapped few-layer structure and the reduced graphene oxide (RGO) shows well-dispersed few-layer structure. Raman spectra analysis indicates that the RGO shows higher B band/G band ratio value than GO, indicating well-restored SP2 carbon atom arrangement and crystal structure. Both fewer-layer GO and RGO were coated on nickel form for supercapacitor electrode application. The GO with sufficient hydroxyl, epoxy and carboxyl groups reveals low conductivity and low current response, which causes low specific capacitance of 0.36, 0.38 and 0.55 F g−1 at 0.5 A g−1 in Na2SO4, KOH and LiOH electrolyte solution, respectively. The RGO with high conductivity reveals the enhanced specific capacitance of 37.12, 51.80 and 61.31 F g−1 at 0.5 A g−1. The LiOH electrolyte with superior ionic diffusion coefficient leads to higher capacitance performance of fewer-layer GO and RGO than other electrolytes. The RGO shows much higher current response than GO at the same scan rate in cyclic voltammetry measurement, which is ascribed to its higher electroactivity. The similar capacitance enhancement of RGO was achieved through cyclic voltammetry-based capacitance and galvanostatic charge/discharge-based capacitance measurements. Accordingly, fewer-layer RGO reveals the superior electrochemical capacitance performance in LiOH electrolyte for the effective energy-storage application.