Enhancement of visible-light photocatalytic activities of BiVO4 coupled with g-C3N4 prepared using different precursors.

Graphitic-like carbon nitride (g-C3N4) photocatalyst was synthesized by a facile chemical pyrolysis method, which was built on the self-condensation of different precursors to generate g-C3N4, e.g., melamine, urea, and thiocarbamide. And the different precursors produced a great influence on the photocatalytic activities of g-C3N4. Heterojunctions of g-C3N4 and BiVO4 were synthesized using a facile solvent evaporation method. The formation of BiVO4/g-C3N4 composites were confirmed by XRD, FT-IR, SEM, XPS, and UV-Vis DRS. The photocatalytic activities for RhB degradation were evaluated under visible-light irradiation. The photocatalytic activity of g-C3N4 prepared by urea was higher than that of g-C3N4 prepared by melamine and thiocarbamide, which was attributed to its favorable dispersibility, larger specific surface area, and higher oxidation capacity. The heterojunction composites exhibited higher photocatalytic activity than pure g-C3N4 or BiVO4. The results showed obvious removal efficiency for RhB, and the optimal sample with a BiVO4 content of 10% exhibited higher efficiency than pure g-C3N4 and BiVO4, and 10 wt%BiVO4/CN-U showed the highest photocatalytic activity. The enhanced photocatalytic activity of BiVO4/g-C3N4 composite can be attributed to the intimate coupling between the two host substrates, resulting in an efficient charge separation.