Understanding the photocatalytic activity of bismuth vanadate phases for solar water splitting: A DFT-based comparative study

Abstract

Bismuth Vanadate (BiVO₄) is a promising candidate for solar water splitting due to its excellent photocatalytic properties. The monoclinic scheelite structure, in particular, is noted for its high-water oxidation activity and has an energy gap of 2.4–2.5 eV. Recently, other phases, especially the tetragonal zircon phase, have also demonstrated interesting photocatalytic properties. Therefore, our study aims to provide a direct comparison of the photocatalytic capabilities of different BiVO₄ structures. To do so, we employed a comprehensive approach to understand the photocatalytic activity of various BiVO₄ crystalline structures, focusing on their structural, electronic, and optical properties using density functional theory (DFT). To describe the electronic properties more accurately, we used corrected density functional theory. We investigated the impact of on-site Coulomb interaction on the structural and electronic properties of BiVO₄. Our results indicate that the monoclinic scheelite structure has a narrow band gap (2.44 eV), light hole effective masses, the largest dipole moment, stronger visible light absorption, and a suitable valence band edge position. These features contribute to its excellent photocatalytic activity, making it a strong candidate for use as a photoanode in photoelectrochemical cells. Moreover, the tetragonal zircon phase exhibits light electron effective masses compared to the scheelite phases, along with suitable conduction and valence band edge positions and a direct band gap. These properties suggest its potential application as a photocathode for solar water splitting. Our findings provide valuable insights into enhancing the overall performance of BiVO₄ for solar water splitting applications, highlighting the distinct advantages of both the monoclinic scheelite and tetragonal zircon phases.