Effectiveness of MnO2 and V2O5 deposition on light fostered supercapacitor performance of WTiO2 nanotube: Novel electrodes for photo-assisted supercapacitors

Abstract

A key approach to overcome the challenges associated with controlling the inherent diversity of sunlight, which targets a global solar energy model, is the development of methods for the storage of solar energy. In the present work, MnO2 and V2O5 have been deposited on WTiO2 nanotube thin films (WTNTS) via the facile and economical chemical bath deposition (CBD) method and used as photoelectrochemical battery type supercapacitors to directly store solar energy. The overall morphology, chemical composition, and wettability characteristics of deposited WTNTS films are affected by the composition of chemical bath deposition. This in turn affects the photoelectrochemical performance and supercapacitor properties of the electrodes studied. WTNTS co-deposited with MnO2 and V2O5 showed the highest specific capacitance. The highest specific capacitance obtained for MnO2-V2O5/WTNTS electrode was 95 mF/cm2 at 0.12 mA/cm2 (237.6F/g at 6.0 A/g) in a 1.0 M LiCl electrolyte. Electrochemical measurements were carried out in the dark and under the light in order to study the impact of light illumination on charge storage performance. Cyclic voltammetry curves show an increase in the area enclosed by the curve, indicating improved charge storage capacity under light illumination in comparison with darkness. Upon light irradiation in the best electrode, the volumetric capacitance value, which is obtained using charging-discharging curves, increased from 38 mF/cm2 (96F/g) to 95 mF/cm2 (237.6 F/g). Excess electron-hole pairs generated as light is illuminated, which contribute to the charge storage under light, are responsible for over 2.5 times the enhanced capacitance. 94% of the capacitance was still maintained in the light illumination after 5000 cycle tests, which showed the outstanding reversibility and cycle stability of the best sample.