Synthesis and supercapacitor electrode of VO2(B)/C core-shell composites with a pseudocapacitance in aqueous solution

VO2(B)/C core-shell composites were successfully prepared using commercial V2O5, glucose and water as the starting materials by a facile one-pot hydrothermal method. The composition of the products was characterized by the techniques including X-ray powder diffraction, infrared spectroscopy, Raman, energy-dispersive X-ray spectrometer and elemental analysis. The morphology of the products was observed by scanning electron microscopy and transmission electron microscopy tests. The results showed the products consisted of the crystal VO2(B) phase and the amorphous carbon phase. The amorphous carbon contained lots of organic groups, such as -OH, C-H, C=O and C=C, etc., which suggested that the carbon here was organic carbon. The morphology of the as-obtained VO2(B)/C composites was well-defined nanobelts, and each VO2(B) core was encapsulated into carbon. Furthermore, the electrochemical properties of VO2(B)/C core-shell composites were investigated by cyclic voltammetry and galvanostatic charge-discharge. The results showed the measured capacitance of VO2(B)/C composites was mainly based on the pseudocapacitance. VO2(B)/C composites displayed the specific capacitance of 203, 190, 182, 173, 164, and 147 F g(-1) at the current density of 0.2, 0.5, 1, 5, 10 and 20 Ag-1, respectively. They also showed an excellent energy density of 198.9 W h kg(-1) at a power density of 504.5 W kg(-1) and a rapidly reversible redox Faraday response. (C) 2016 Elsevier B.V. All rights reserved.