Enhanced photo-degradation methyl orange by N-F co-doped BiVO_4 synthesized by sol-gel method

摘要

Using ammonium fluoride (NH4F) as the source of nitrogen (N) and fluorine (F),N-F co-doped bismuth vanadate (BiVO_4) visible-light-driven photocatalysts have been synthesized via a sol-gel method. The resulting materials were characterized by a series of techniques: X-ray photoelectron spectroscopy, X-ray diffractometry, scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface analysis, and UV-vis diffuse reflectance spectroscopy. Compared with BiVO_4, the N-F co-doped BiVO_4 photocatalysts exhibited much higher photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. It was revealed that N and F atoms were doped into the lattice of BiVO_4. The doped N atoms existed as O-N or V-O-N bonding, and the F atoms replaced some O atoms to form the O-V-F structure, which can be attributed to the appearance of more active species V~(4+) and oxygen vacancies. The doped N and F atoms resulted in a red shift in the absorption edge. However, the N and F doping only slightly changed the morphologies and BET special surface areas of the samples. The photocatalytic activity of BiVO_4 significantly depended on the N-F doping content and the calcination temperature. The maximum activity was observed for the catalyst obtained with calcination at 500 ℃, a molar ratio of NH_4F to Bi(NO_3)_3 was 6%.