New Synthesis Of Semiconductor Composites M/TiO₂ (M=PZT, PS) With High Photocatalytic Activity

Presently, visible-light TiO₂ based photocatalysts coupled with narrow bandgap semiconductors are either unstable (CdS, CdSe, etc.) or have low conversion efficiency of photo-generated carriers. How to efficiently exploit visible light active photocatalysts for degradation of environment pollutants with chemical stability has attracted much attention in recent years. In this paper, two relative narrow bandgap semiconductor, porous silicon (PS 2.0 eV) and lead zirconate titanate (PZT 2.5 eV) have been firstly applied in photocatalytic field. Herein, PZT/TiO₂ and PS/TiO₂ composites have been prepared for the first time. Mechanisms are proposed to elucidate the high photocatalytic activity of composites during degradation of organic pollutants.Titanium dioxide (TiO₂) nanoparticles were prepared by sol-gel method. Hydrothermal method was used to synthesize nanoparticles of PZT with no Pb pollutant to our environment during preparing process. The simple chemical etching method was applied to producing PS with low cost. In this dissertation, simple coupled method was employed to prepare PZT/TiO₂ and PS/TiO₂ composites. All of composite were calcinated at 673 K and used as visible-light photocatalysts in the experiments. X-ray diffraction (XRD), photoluminescence (PL), N2 adsorption Brunauer -Emmett- Teller (BET) method, UV-Visible diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM) were used to characterize the structure and composition of samples including crystal phase composition, crystalline sizes, optical property, typical specific surface area, light absorption, lattice structure and surface chemical state, respectively. Time-resolved surface photoconductivity (TRSP) and electron spin resonance (ESR) were used to probe the possible mechanism in the photocatalytic process.The phtocatalytic activity of novel composites was evaluated by degradation of Rhodamine B (RhB) in aqueous solution. The PZT/TiO₂ and PS/TiO₂ composites show much greater activity than that of separate PZT, PS, self-made TiO₂, the commercial photocatalyst P25, or many other visible irradiated photocatalysts in used.