Synthesis of nanosized vanadium pentoxide/carbon composites by spray pyrolysis for electrochemical capacitor application
Nanostructured vanadium pentoxide/carbon (V2O5/carbon) composite powders with enhanced specific capacitance were synthesized by the spray pyrolysis technique. Electrochemical properties were examined by the cyclic voltammetry technique. Following analysis of powders sprayed at different temperatures, composite powders obtained at an optimum temperature of 450 °C yielded a maximum specific capacitance of 295 F g−1 in 2 M KCl electrolyte at a 5-mV s−1 scan rate. The weight percentage of carbon-related species was 2.7 wt% in this V2O5/carbon composite, as detected by thermogravimetric analysis (TGA) and confirmed by transmission electron microscope energy dispersive spectroscopy (TEM-EDS) analysis. Following initial X-ray diffraction (XRD) characterization, scanning electron microscope (SEM), TEM and high-resolution TEM (HRTEM) imaging revealed a specific morphology of spherical shell agglomerates of V2O5 nanorods and nanoribbons, with each shell comprising a network of these one- and two-dimensional nanoparticles in an amorphous carbon matrix. The V2O5 network was not fully dense, and the majority of the nanorod sizes were in the range of 50–150 nm, with additional long nanoribbons extending from the outsides of the spherical shells. The specific surface area was 18 m2 g−1 for the composite powders, and the pore size distribution revealed that the majority of pores had diameters in the range of 40–50 Å, which was relatively larger than the pore diameters obtained at 500 °C and would be beneficial for electrochemical performance. The enhancement of the specific capacitance in V2O5/carbon composites was attributed to the distribution of amorphous carbon throughout the V2O5 and the particular open nanostructure.