Study Of SnS₂,Bi-based Photocatalysts By Surface/interface Engineering And Its Enhanced Photocatalytic Activity For Degradation Of Pollutions

In recent years, the photocatalysis, which is on the basis of the semiconductor materials, has attracted wide attentions because it can provide a clean and efficient way for us to solve the global environmental pollution problems. However, the narrow spectral response range and low photo quantum efficiency of the existing photocatalysts such as TiO2 has limited its application. Therefore, how to modify the photocatalysts for improving the utilization rate of incident light, improving the effective separation of photo-induced electrons and holes and avoiding the recombination inside or on the surface of the photocatalysts always is the key of the photocatalysis study. For this reason, semiconductor coupling and facets control are used to adjust and control the surface/interface of SnS2 and bismuth-based composite photocatalysts for improving the spectral response range and separation of photo-induced carriers of the as-prepared photocatalysts in this work. And the as-prepared photocatalysts were used in the field of environmental purification, such as decomposition of organic pollutants in water and air and reduction of heavy metal ions respectively. The main research work is as follows:Bi12GeO20 photocatalysts with different sizes and morphologies were synthesized by hydrothermal method and sol-gel method respectively. The phase composition, morphology and optical absorption performance were analyzed by a variety of characterizations. The facets and morphology transformation process of the as-prepared Bi12GeO20 samples were analyzed by FESEM. Meanwhile, RhB aqueous solution and gaseous formaldehyde were chosen as the model organic pollutant to study the photocatalytic activities and the related mechanism of the as-prepared Bi12GeO20 samples. The results indicate that the tetrahedron-shaped Bi12GeO20 sample with exposed {111} facets has the enhanced photocatalytic activity because of its special surface atomic arrangement, which is good for photocatalyst to improve the adsorption of O2.Bi12GeO20 nanocrystals were synthesized by a sol-gel method and then coupled with g-C3N4 to prepared novel visible light Bi12GeO20/g-C3N4 composites. XRD, SEM, TEM/HRTEM, XPS, FT-IR, UV-vis DRS, PL and other characterizations were used to study the phase composition, morphology, optical absorption performance and separation efficiency of photo-induced charges of the as-prepared composites. The results of photocatalytic degradation of RhB and photocatalytic reduction of Cr(VI) indicate that the as-prepared Bi12GeO20/g-C3N4 composites have the enhanced photocatalytic activity compared with the pure Bi12GeO20 or g-C3N4. The main reason is that, on the one hand, the Bi12GeO20/g-C3N4 composites have the better optical absorption ability compared with the pure Bi12GeO20. On the other hand, the fabrication of the heterosturctures accelerated the separation of the photo-induced charges.Bi2SiO5/AgI composites were synthesized by a simple in situ precipitation method. The phase composition, morphology and optical absorption performance were analyzed by a variety of characterizations. FESEM and HRTEM demonstrated that the Bi2SiO5 has a plate-like structure and the top and bottom surfaces are exposed with {100} facets. Meanwhile, ARG aqueous solution and gaseous formaldehyde were chosen as the model organic pollutant to study the visible light photocatalytic activities and the related mechanism of the as-prepared Bi2SiO5/AgI composites. The results indicate that the inner electric field induced by the exposed {100} facets of the Bi2SiO5 nanoplates and the proper band position of the Bi2SiO5/AgI composites effectively accelerate the migration of photo-induced electrons and holes, extend the life of the photo-induced carriers and improve the photo quantum efficiency, giving rise to the enhancement of the photocatalytic activity of the Bi2SiO5/AgI composites.SnS2 nanosheets with exposed {001} facets were synthesized by a solvothermal method. XRD, XPS, SEM, TEM/HRTEM, UV-vis DRS and other characterizations were used to study the phase composition, morphology and optical absorption performance of the as-prepared SnS2 samples. RhB and Cr(VI) aqueous solutions were chosen as the model pollutant to study the photocatalytic activities and the related mechanism of the as-prepared SnS2 samples. The results indicate that the special surface atomic arrangement of the {001} facets of the as-prepared SnS2 nanosheets induced an inner electric field which is perpendicular to the {001} facets. This inner electric field will improve the separation efficiency of the photo-induced electrons and holes and result in the enhanced photocatalytic activity of the SnS2 nanosheets with exposed {001} facets.