Template synthesis of hollow carbon spheres anchored on carbon nanotubes for high rate performance supercapacitors

A carbon material consisting of hollow carbon spheres anchored on the surface of carbon nanotubes (CNT-HCS) has been synthesized by an easy chemical vapor deposition process using a CNT-MnO2 hybrid as template. An electrode made of this material exhibits a maximum specific capacitance of 201.5 F g(-1) at 0.5 A g(-1) and excellent rate performance (69% retention ratio at 20 A g(-1)). It has impressive cycling stability with 90% initial capacitance retained after 5000 cycles at 5 A g(-1) in 6 mol L-1 KOH. Symmetric supercapacitors based on CNT-HCS achieve a maximum energy density of 11.3 W h kg(-1) and power density of 11.8 kW kg(-1) operated within a wide potential range of 0-1.6 V in 1.0 mol L-1 Na2SO4 solution. (C) 2012 Elsevier Ltd. All rights reserved.