Influence of the electrochemical properties of vanadium oxides on specific capacitance by molybdenum doping

Abstract

Molybdenum (Mo)-doped vanadium dioxide ($\hbox {VO}_{2}$(B)) nanobelts were successfully synthesized using commercial vanadium pentoxide ($\hbox {V}_{2}\hbox {O}_{5}$) as the starting material and ammonium molybdate as the dopant by a simple hydrothermal route. Then, Mo-doped $\hbox {VO}_{2}$(B) nanobelts were transformed to Mo-doped $\hbox {V}_{2}\hbox {O}_{5}$ nanobelts by calcination at $400{^{\circ }}\hbox {C}$ under an air atmosphere. The samples were characterized by X-ray powder diffraction, energy-dispersive X-ray spectrometer, elemental mapping, X-ray photoelectron spectroscopy, X-ray fluorescence and transmission electron microscopy techniques. The results showed that Mo-doped $\hbox {VO}_{2}$(B) and $\hbox {V}_{2}\hbox {O}_{5}$ solid solution with high purity were obtained. The electrochemical properties of Mo-doped $\hbox {VO}_{2}$(B) and $\hbox {V}_{2}\hbox {O}_{5}$ nanobelts as supercapacitor electrodes were measured using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The specific capacitance of $\hbox {VO}_{2}$(B) nanobelts slightly declines with Mo doping, however, the specific capacitance of $\hbox {V}_{2}\hbox {O}_{5}$ nanobelts greatly improves with Mo doping. Mo-doped $\hbox {V}_{2}\hbox {O}_{5}$ nanobelts exhibit the specific capacitance as high as 526 F $\hbox {g}^{-1}$ at the current density of 1 A $\hbox {g}^{-1}$. Both CV and GCD curves show that they have good rate capability and retain 464, 380, 324 and 273 F $\hbox {g}^{-1}$ even at a high-current density of 2, 5, 10 and 20 A $\hbox {g}^{-1}$, respectively. It turns out that Mo-doped $\hbox {V}_{2}\hbox {O}_{5}$ nanobelts are ideal materials for supercapacitor electrodes in the present work.