Light-chargeable two-electrode photo-supercapacitors based on MnS nanoflowers deposited on V2O5-BiVO4 photoelectrodes

Abstract

Self-powered energy devices are essential devices for application in future portable electronics. The self-powered applications of photo-supercapacitors (PSCs), as dependable energy harvesting devices, have been investigated using the photovoltaic effect of supercapacitors. In this work, a simple electrodeposition method has been used to successfully prepare novel, flower-like MnS@V₂O₅-BiVO₄. Different analytical methods have been used to study the phase composition, morphology, and photoelectrochemical properties of the prepared samples. The best MnS@V₂O₅-BiVO₄ electrode (sample S1) showed a high average 41.6 F/g specific capacitance at a current density of 10 µA/cm², which is 7.5 times the equivalent value for the bare V₂O₅-BiVO₄ electrodes. An improved photocurrent density of 115 µA/cm² was also shown by this sample after 1 cycle of MnS deposition, which is about 3.3 times higher than the corresponding value for the bare sample. The poor electron-hole separation of bare samples can be overcome by the improved photocurrent density. The effect of light illumination on charge storage performance was investigated by different electrochemical techniques in the dark and under light illumination. The best MnS@V₂O₅-BiVO₄ electrode synthesized, sample S1, showed real capacitance values of 10 and 6.3 F/g (@20 mV/s) and 41.6 and 6.3 F/g (@10 μA/cm²) prior to and following light illumination, respectively, due to the extension of the discharge time by the charge carriers produced under light excitation and contribution of excess generated electron-hole pairs to the charge storage. In addition, a symmetric supercapacitor has been prepared using the best MnS@V₂O₅-BiVO₄ with a maximum energy density of 7.0 Wh/kg at a 250 W/kg power density (@0.1 mA/cm²) and stable capacitance retention after 3000 cycles. In addition, the best MnS@V₂O₅-BiVO₄ electrode and MnS/graphite asymmetric supercapacitors have been prepared with 3.0 × 3.0 cm² dimensions. The device is charged under light irradiation and can easily turn on LED light, which indicates its potential practical applications as an appealing energy storage device. The remarkable performance makes MnS@V₂O₅-BiVO₄ a promising compound for energy storage purposes.