New photoelectrodes based on bismuth vanadate-V2O5@TiNT for photo-rechargeable supercapacitors

Abstract

The preparation of an optically responsive supercapacitor is reported in this work. The electrode material has been prepared through electrodeposition of bismuth vanadate‑vanadium(V) oxide (BVO-V2O5) on the titania nanotubes (TiNT). The impacts of deposition time on the morphology as well as the supercapacitor and photoelectrochemical characteristics have then been investigated. New electrodes show a considerable specific capacitance of 288 mF/cm2, which is 15 times higher than that of the bare TiNT electrode under light irradiation, and a high energy density of 40 mWh/cm2 at a power density of 0.24 mW/cm2. Moreover, the electrodes show outstanding energy storage performance with 99.7 % capacitance retention during 4000 charge-discharge cycles, which indicates their promising potential applications in the areas of energy storage and conversion. The specific capacitance of the best BVO-V2O5@TiNT sample increases by 65 % (288 mF/cm2 at 0.12 mA/cm2) upon light illumination in comparison with the corresponding value in the dark (100 mF/cm2 at 0.12 mA/cm2). The photo-charging and galvanostatic discharging of the device have also been studied. The maximum photocharged areal capacitance value was found to be 290 mF/cm2 at a current density of 0.016 mA/cm2. However, the areal power and energy densities at this current density were 5.44 and 0.91 mW/cm2, respectively. A facile method for the synthesis of cheap, photo-rechargeable supercapacitors and the development of a photo-supercapacitor, which integrates photoelectric conversion and energy storage in a single, fast charging, and self-powering device is reported.