Au-doped BiVO4 nanostructure-based photoanode with enhanced photoelectrochemical solar water splitting and electrochemical energy storage ability

Highlights: • Au-doped BiVO₄ nanostructures were prepared using a simple ultra-sonication method. • The 5Au-BV electrode showed reduced electron transfer resistance over other electrodes. • The 5Au-BV photoelectrode showed 29-times greater photocurrent density over pure electrode. • 5Au-BV electrode displayed greater PEC performance and specific capacitance storage ability. BiVO₄ is an appropriate photoanode material for solar-powered photoelectrochemical (PEC) water splitting and electrochemical energy storage. However, it has a few drawbacks. Therefore, doping with noble metals is speculated to be a promising technique to overcome these. Moreover, the role of the doped noble metal in the improvement of the water oxidation kinetics and energy storage has not been studied adequately so far. In this study, we prepared Au-doped BiVO₄ nanostructures using a simple template-free ultrasonication technique. The effect of Au doping on the optical properties and surface morphology of the BiVO₄ nanostructures, and their performance as a photoanode for energy harvesting are explored comprehensively. The 5Au- BiVO₄ photoelectrode displayed a considerable improvement (~29 times) in the PEC photocurrent density compared to that of the pure BiVO₄ photoanode. Electrochemical impedance spectroscopy studies confirmed that the dopant improved the charge carrier density and acted as an electron donor. Furthermore, it was confirmed that the photocurrent density at 1.23 V vs. the reversible hydrogen electrode increased after Au doping. The supercapacitor properties of the 5Au-BiVO₄ electrode were studied by cyclic voltammetry. At a 10 mV s⁻¹ scan rate, the specific capacitance of the 5Au-BV electrode increased to ~2.1 times that of the pure electrode. The significantly improved PEC performance and supercapacitor properties of the 5Au-BiVO₄ electrode are attributed to its higher conductivity, improved interfacial charge transfer at the surface of BiVO₄, and the synergistic effect between the host and dopant.