Hollow melamine resin-based carbon spheres/graphene composite with excellent performance for supercapacitors

Hollow melamine resin-based carbon spheres (HMCS) clad in graphene (GN) sheets brought an unique three-dimensional (3D) network architecture after the pyrolysis of the melamine-formaldehyde (MF) resin spheres/graphene oxide composite under argon. Polyvinyl alcohol plays an important role in controlling the size and the structure of the MF resin spheres and can induce the formation of hollow nitrogen-containing carbon spheres to produce the HMCS/GN composite after anneal treatment. The diameter of the HMCS can be tuned by changing the carbonization temperature. The HMCS/GN annealed at 600 degrees C exhibits excellent electrochemical performance making it an ideal electrode material for supercapacitors. High specific capacitance of 720 F g(-1) at a current density of 0.2 A g(-1), 560 F g(-1) at 5 A g(-1) and 420 F g(-1) at 20 A g(-1) can be achieved which indicates ideal rate capability. The specific capacitance retains 80.3% after 10000 charge-discharge processes at a current density of 20 A g(-1). The excellent electrochemical performance of the HMCS/GN is ascribed to its unique 3D network architecture constructed by the hollow carbon spheres intercalated in GN sheets and the high nitrogen content of the composite. (C) 2015 Elsevier Ltd. All rights reserved.