Enhancement of Visible-Light Catalytic Activity for Zn Doped OV--Bi₂O₃: Regulation of Electronic Structure and Promotion of Charge Separation

A novel Zn-doped beta-Bi2O3 nanomaterial (OV-Zn: Bi2O3) with two crystal defects, oxygen vacancy (OV) and doped Zn2+, was prepared via a sol-gel method followed by in. situ carbon thermal reduction treatment. The concentration of OV of OV-Zn:Bi2O3 sample can be modulated by regulating the content of doped Zn2+. As a reference, the novel beta-Bi2O3 having OV but without doped Zn2+ (OV-beta-Bi2O3) was also synthesized via a similar process. The comprehensive effect of OV and doped Zn2+ on the visible-light-activity of OV-Zn:Bi2O3 for the degradation of methylene blue (MB) and 2,4,6-trichlorophenol (2,4,6-TCP) was investigated by ultraviolet-visible light diffuse reflectance spectra,X-ray photoelectron spectra,electron spin resonance, photoluminescence spectrum and photoelectro-chemical measurements. The results show that introduction of OV can not only drastically extend the photoabsorption into longer wavelength region but also promote the separation of photo. generated charge carriers. So, compared to traditional beta-Bi2O3, OV-beta-Bi2O3 demonstrated highly promoted activity for the degradation of methylene blue (MB) and 2,4,6-trichlorophenol (2,4,6-TCP). For OV-Zn:Bi2O3 catalysts, Znic doping can make the valence band edge of catalysts move down and the oxidation ability of photo. excited holes increase. And appropriate amount of zinc doping can also improve the separation efficiency of photogenerated carriers. In contrast to OV-beta-Bi2O3, the visible light activity of OV-Zn:Bi2O3 was further improved and OV-Zn:Bi2O3-0.3 with a molar ratio (n(Zn)/n(Bi)) of 0.3 exhibited the highest activity for the degradation of MB and 2,4,6-TCP.