Novel eco-friendly synthesis of graphene directly from graphite using 2,2,6,6-tetramethylpiperidine 1-oxyl and study of its electrochemical properties

Herein we report a simple, low cost, highly efficient and environment friendly one-pot method for the high throughput synthesis of graphene directly from graphite using 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and H2O2 under microwave irradiation. The formation mechanism of graphene nanosheets (GNS) as investigated by Raman spectroscopy and electron microscopy techniques reveal surface defect generation, intercalation and exfoliation as the main steps. The rapid and local Joule heating of graphite by microwave radiation results in simultaneous deoxygenation and exfoliation forming GNS. The as-synthesized GNS are a few layer thick with a high surface area of 937.6 m(2) g(-1) and a high C/O ratio of 9.2. These results open the perspective of replacing toxic oxidizing and reducing agents by environment friendly chemicals of similar efficacy, thus facilitating the large-scale production of GNS by a greener method. Furthermore, GNS exhibits good electrochemical performance with a large specific capacitance (197 F g(-1)), excellent rate capability and a long cycle life (1000 cycles) in neat 1-ethy1-3-methylimidazolium tetrafluoroborate (EMIMBF4) electrolyte. It also has a high energy density of 76.03 W h kg(-1) while simultaneously possessing a high power density of 1.12 kW kg(-1). (C) 2014 Elsevier B.V. All rights reserved.