Facile Phase Control and Photocatalytic Performance of BiVO₄ Crystals for Methylene Blue Degradation

Emerging contaminants, which mainly exist as organic pollutants and pose adverse biological effects, could be removed using photocatalytic degradation, resulting in a low-cost and environmentally friendly solution. Herein, BiVO₄ nanoparticles with different morphologies and photocatalytic performances were synthesized by hydrothermal treatment at different residence times. The XRD and SEM results indicate that the crystal phase of BiVO₄ gradually transformed from a single tetragonal phase to a single monoclinic crystal phase as the hydrothermal time increased, and with the extension of the hydrothermal time, the morphology of BiVO₄ nanoparticles gradually differentiated from a smooth spherical shape to flower-like shapes composed of polyhedrons; the size of the crystals also increased accordingly. Methylene blue (MB), used as a probe of organic pollutants, was degraded under visible light irradiation by all BiVO₄ samples to investigate its photocatalytic activities. The experimental results show that the longer the hydrothermal time, the better the photocatalytic performance. The optimum hydrothermal time was 24 h, at which the sample showed the highest photocatalytic activity for MB degradation. This work shows a convenient strategy for control of the crystal phase of BiVO₄-based photocatalysts based on the understanding of the crystal morphology evolution mechanism, which will benefit the researchers in designing new BiVO₄-based photocatalysts with high efficiency for emerging contaminants' degradation.