Characterization and photoelectrochemical evaluation of BiVO4 films developed by thermal oxidation of metallic Bi films electrodeposited

This paper reports the synthesis, characterization, and photoelectrochemical evaluation of BiVO4 thin films. Bi thin films were obtained by electrodeposition and then thermally oxidized. Before thermal oxidation, the vacuum annealing temperature of the metallic Bi films significantly changed the final properties. Increasing the annealing temperature of the samples reduced their thickness and increased compaction and the growth in grain size. At the same time, this increase reduced the energy band gap, improved the electrical properties, including the charge carrier absorption and transport, and broadened the Urbach energy. The best performance was obtained with a film vacuum annealed at 10 mTorr and 200 °C, while the thin film annealed at 250 °C showed a deterioration of the material. The energy band gap ranged from 2.44 to 2.53 eV, while the calculated carrier density ranged from 6.24 × 1017 to 3.70 × 1018 cm−3. Based on Mott-Schottky plots, these materials exhibited Vfb of 0.441–0.611 V vs. NHE, making them suitable for photoanodes in solar water splitting and promising routes for hydrogen production.