Controllable Synthesis and Photocatalytic Performance of BiVO4 under Visible-light Irradiation

Visible-light-driven photocatalyst BiVO4 was synthesized via a facile microwave-hydrothermal method using BiVO3.5H(2)O and NH4VO3 as raw materials. Crystal structure of BiVO4 photocatalyst could be selectively controlled to be tetragonal or monoclinic by simply adjusting the pH of the precursor solution. The prepared samples were characterized by XRD, UV-Vis, Raman, and SEM. The mechanism of BiVO4 formation with different crystal structures was discussed. Meanwhile, the photocatalytic performances of the prepared sample were evaluated by degradation of methylene blue and photocalytic oxidation of NO gas in air under visible light irradiation. The results showed that BiVO4(z-t) microsphere was obtained when the precursor pH is 3-5, but when the pH is less than 2 or greater than 7, the as-prepared powders are BiVO4(s-m) with polyhedron morphology. This may be due to the change of pH that could form transformation of vanadate and bismuth ion in the precursor solution, and then affect the formation process of BiVO4 , resuting in the change of crystal structure, morphology, crystal surface, and VO4 tetrahedron of BiVO4(s-m). The photocatalytic tests indicated that the activity of BiVO4(s-m) was much better than that of BiVO4(z-t). The BiVO4(s-m) sample prepared at pH 9 exhibits excellent visible-light photocatalytic activity, because of its higher crystalline, preferentially exposed facts (040), and higher degree distortion of VO43- tetrahedron.