The Prepared La <sub> Of High Temperature Vulcanized 3 </ Sub> NbS <sub> 2 </ Sub> O <sub> 5 </ Sub> And Its Visible Light Photocatalytic Performance Studies

Visible light responsive semiconducting photocatalytic materials with narrow band gap have been the research focus of heterogeneous semiconductor photocatalysis in recent decades. Oxysulfide which avoids traditional sulfide visible light photocatalysts'corrosion, instability, and has a strong visible-light absorption property, has been an important direction for designing and synthesizing new visible-light responsive photocatalysts. Current domestic and foreign research progresses on preparation and application heterogeneous semiconductor photocatalysts were given a detailed overview in this paper. To circumvent the shortcoming solid state reaction, perovskite structure photocatalyst La3NbS2O5 was prepared by H2S gas sulfurization method firstly. The photocatalytic activities of La3NbS2O5 was studied by photocatalytic degradation of methylene blue under visible light irradiation.H2S gas sulfurization (HGS) method:amorphous precursor La3NbO7 was prepared by simple citric acid complex method, and then was sulfurized by H2S gas at high temperature. Photocatalysts La3NbS2O5 were prepared by HGS method, and were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET) and UV-Vis diffuse reflectance spectra (UV-Vis DRS) in this paper, which were also compared with samples prepared by solid state reaction(SSR) method. The results indicated that, compared to SSR method's 1000℃calcination for 96 h, pure La3NbS2O5 crystal phase with Ruddlesden-Popper-type layered perovskite structure could be obtained after sulfurization at 700℃just for 1h by HGS method. The degree of crystallinity and grain size increase with raise of sulfuration time and temperature. The samples are ball-like regular particles, whose particle size was small (100-600 nm) and well distributed. As sulfuration temperature increases, particle size of La3NbS2O5 will increase with emergence of slight agglomeration, while specific surface area will decrease gradually (11.39→5.81 m2/g). UV-Vis DRS results suggest that the as-prepared samples have an apparement absorption characteristic in the visible light region (400-600 nm), whose absorption band edge is 650 nm. The band gap energy of La3NbS2O5 is estimated to be 1.9 eV, which can response to visible light.The photocatalytic activities of La3NbS2O5 were investigated by photocatalytic degradation of methylene blue under visible light (λ>400 nm) irradiation. The effects of sulfurization temperature, sulfurization time, photocatalyst concentration, H2O2 dosage and pH of initial solution and preparation method were studied in detail. The results indicated that the optimum photocatalyst was prepared by sulfurization at 800℃for 1 h. The optimum dosage of photocatalyst is 3 g/L, alkaline environment is conducive to improve the photocatalytic properties, and the optimum dosage of H2O2 is 8 mL/L. The degradation rate of methylene blue of La3NbS2O5 (HGS) is up to 92.7% in 12 h, which is obviously higher than that of La3NbS2O5 synthesized by solid-state reaction method.