Bismuth vanadate thin films for efficient photoelectrochemical water splitting

Monoclinic bismuth vanadate has attracted much attention as one of the efficient photoanode materials that can harvest a wide range of visible light to split water efficiently. In this study, we report the preparation of nanoporous BiVO4 via wet chemical approach coupled with dip-coating technique. The monoclinic scheelite phase of BiVO4 is revealed by X-ray diffraction (XRD). Characterisation techniques like Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and scanning electron microscopy (SEM) have been analysed and confirmed the formation of BiVO4 layers on FTO. Photoelectrochemical studies of BiVO4 thin films have been performed in a three-electrode potentiostat system, illuminated under visible light-emitting diode (LED) source of intensity 100 mW/cm2. The optimised 10 layered BiVO4 thin film with average thickness of ~ 300 nm shows an optimum photocurrent density of ~ 0.67 mA/cm2 at 1.23 V vs RHE and photoconversion efficiency of 0.4% at 1.23 V vs RHE as compared with different layered BVO photoanodes. The measurements of flat band potential and confirmation of n-type behaviour of BiVO4 semiconductors were carried out by Mott–Schottky analysis. Electrochemical impedance spectroscopy (EIS) study clearly indicate the less charge transfer resistance and high hole transfer mobility of optimised BiVO4 photoanode films.