Hydrothermally in-situ Deposited BiVO4 Crystals Via a Seed-free Approach and its Application in Water Treatment and Hydrogen Generation

Thin films of Bismuth Vanadate (BiVO4)crystals are deposited on bare FTO substrates using hydrothermal method. The samples are annealed in a temperature range from 450 oC to 550 oC. X-Ray Diffraction (XRD) pattern of the prepared BiVO4 thin films confirms its monoclinic structure. Scanning Electron Microscopy (SEM) images determine the truncated bipyramid shape of the crystals while a significant number of crystals expose their high photoelectrochemically active facet. By controlling and optimizing parameters such as temperature, deposition time, precursor concentration, and annealing temperature, a uniform and robust BiVO4 layer is synthesized. Finally, the optimum BiVO4/FTO layer is prepared at 120 oC for at least 4 hours by using a 0.027M BiVO4 precursor solution with a pH of 1.2. In order to have a measurement for the application of the fabricated crystals in water treatment and Hydrogen generation, the linear sweep voltammetry (LSV) measurements of samples are measured and compared. The LSV tests show a photo-response up to 70 µA/cm2 at V=1 V (vs Ag/AgCl) for BiVO4/FTO samples annealed at temperatures higher than 500 oC. In addition, a simple model are proposed to understand the growth behavior of BiVO4 crystals under different growth conditions.