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

Abstract 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.