Controlled synthesis and structural modulation to boost intrinsic photocatalytic activity of BiVO4

Abstract

Modulation of the structure, composition, and morphology through a simple refinement of the synthetic parameters is central to obtaining signature catalytic properties, enabling an understanding of the underlying growth and reaction mechanisms. In this study, a bismuth vanadate (BiVO₄) model photocatalyst with several nanostructures (including pillar-like, dendrites, and microgranules) was fabricated by simple hydrothermal, solvothermal, and solid-state reaction (SSR) methods. As the solvothermal reaction temperature was increased, the tetragonal phase transformed into a monoclinic phase, and the inorganic nuclei interacted, self-assembled, and grew continuously to yield a well-defined architecture indicating the critical role of temperature in stabilizing the crystal structure and surface atomic features principally in an ethanol/water mixture. In contrast, conventional hydrothermal synthesis (only water as a solvent) resulted in single-phase BiVO₄ pillars enriched with rough surfaces, sharp edges, and porous structures. The growth mechanism of the BiVO₄ dendrites was investigated by the morphological evolutions from different reaction products obtained under different reaction conditions. BiVO₄ has a bandgap energy in the visible spectral range (2.50–2.27 eV). Hence, BiVO₄ architectures with exclusively controlled surfaces and crystal structures can be used as efficient photocatalysts to remove organic pollutants (methylene blue dye) in water. The solvothermally prepared BVO-SLR’24 with a mixed-phase (monoclinic and tetragonal zircon) structure exhibited superior photocatalytic activities for the decomposition of organic contaminants, which may be due to the unique connectivity between crystals, accelerated electron transfer, and heterojunction formation, compared to BiVO₄ prepared with pure phase pillars and microgranules. This work highlights the significance of synthesis methodology and microstructural modification with the photophysical properties to reinvigorate the conventional design of visible-light-driven (VLD) photocatalysts.