The Preparation And Performance Study Of Novel Semiconductor Heterogeneous Visible Light Photocatalyst

Semiconductor photocatalysis has received considerable attention since its potentialapplication for energy and environmental fields. The sunlight utilization of traditionalphotocatalysts (such as TiO2, ZnO, SnO2) is very limited due to their wide band-gap. Thus, thedevelopment of novel visible light photocatalytst has become one of the hot spots in the field ofphotocatalysis, and the construction of heterogeneous composite photocatalytst by coupling oftwo semiconductors is an effective method to realize this purpose. The purpose of thisdissertation is the development of novel visible light photocatalytst, and thus preparesmesoporous CdS/layered titanate composite photocatalyst, C3N4-Bi2WO4compositephotocatalyst, and C3N4-BiVO4composite photocatalyst by coupling of two semiconductors. Thestrcture and propery of obtained composite photocatalysts were characterized by XRD, SEM,TEM, FT-IR, UV-vis and so on. The photocatalytic activity of photocatalysts was evaluated bythe degradation of organic dyes. The detailed works were summarized as follows:1. A mesoporous CdS/layered titanate composite photocatalyst has been synthesized via anexfoliation-restacking and the subsequent sulfuration route. The obtained compositephotocatalyst exhibited an enhanced visible light harvesting, as well as a large surface area.Moreover, this material contained two kinds of mesoporous structures derived from therestacking of nanosheets and the pillaring of CdS nanoparticles, respectively. The results ofphotodegrading rhodamine B under visible light illumination suggested that this CdS/layeredtitanate composite photocatalyst possessed a high activity compared with its layered titanateprecursors and the Cd2+intercalated form.2. C3N4was hybridized by Bi2WO6via a hydrothermal method. The HR-TEM results revealedthat an intimate interface between C3N4and Bi2WO6to form in the composite photocatalysts.The UV-vis diffuse reflection spectra showed that the resulting C3N4-Bi2WO6compositephotocatalysts possessed more intensive absorption within the visible light range in comparisonwith pure Bi2WO6. These excellent structural and spectral properties endowed the C3N4-Bi2WO6composite photocatalysts with enhanced photocatalytic activities. Significantly, the optimumphotocatalytic activity of the0.5C3N4-0.5Bi2WO6composite photocatalyst for the degradation ofmethyl orange was almost3and155times higher than those of either individual C3N4or Bi2WO6.3. C3N4-BiVO4composite photocatalysts were obtained by a hydrothermal method with C3N4and the precursor of BiVO4. The visible light absorption ability of resulting compositephotocatalysts is more intensive compared with pure C3N4. The photocatalytic tests furtherdemonstrated that C3N4-BiVO4composite photocatalysts possessed obviously enhanced visiblelight photocatalytic activities. In addition, trapping experiments revealed that superoxide radicalspecies as the mainly active species for the degradation of methylene blue.