Promoted Photo-oxidation Reactivity of Particulate BiVO[sub 4] Photocatalyst Prepared by a Photoassisted Sol-gel Method

Bismuth vanadate ( BiVO 4 ) powder with a scheelite-monoclinic (s-m) structure was synthesized by a photoassisted sol-gel method, i.e., a modified sol-gel method including an additional procedure in which a mixed solution of BiCl 3 , VO ( OC 3 H 7 ) 3 , and sodium isopropoxide was irradiated with UV light before hydrolysis. The BiVO 4 powder prepared by the photoassisted sol-gel method (called P-sample) exhibited 1.3–3 times higher activity in oxygen photoevolution reaction than that prepared by the conventional nonphotoassisted sol-gel method (called N-sample), indicating that the photoassisted sol-gel method is effective for improving the photocatalytic activity of BiVO 4 . X-ray diffraction patterns and UV-visible absorption spectra were the same between the P- and N-samples, whereas SEM inspection showed that the P-sample was composed of well-separated small-size particles, compared with the N-sample. X-ray photoelectron spectroscopy inspection also exhibited that the P-sample had a thin surface layer containing Bi 5 + and OH − . It is discussed that the high activity of the P-sample is attributed either to the small size of BiVO 4 particles or a certain catalytic action of the surface layer containing Bi 5 + and OH − .