Fabrication Of TiO₂-noble Metal Composite Plasmonic Photocatalyst And The Degradation Of Phenol In Visible Light

Recently, with the development of modern industry, the quantity of organic pollution wastewater such as phenols wastewater discharging into the environment has been increased year by year. Due to its chemical stability, phenols can’t be degraded naturally and thoroughly, and its toxicity and biological concentration will damage human health seriously. Among the methods for disposing phenols, the photocatalysis degradation attracts people’s attention with its simple operation, energy saving, high efficiency and non-secondary pollution. Titanium dioxide is the most important and promising photocatalyst because it exhibit a high durability, high oxidation ability, high chemical stability and the possibility to use solar spectrum. However, there are many important drawbacks that limit the application of titanium dioxide photocatalyst. For example, its quantum yield is low and the band gap is high. Aimed at the problems, the surface plasmon resonance nanoparticle composited with TiO2were fabricated. The morphology and microstructure characteristics of prepared photocatalyst were characterized by means of the scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrum (EDS), N2adsorption-desorption measurements (BET), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectra (DRS). Their degradation activity of phenol in visible light and the photocatalytic mechanism was investigated and explained.The main research content and results were summarized as follows:Noble metal doped TiO2nanocomposite with high photocatalytic activity were synthesized through a photo-reduction deposition method, which take HAuCl4·4H2O as Au source, AgNO3as Ag source. The photocatalytic activity were evaluated by degradation of phenol under visible light irradiation. The characterization results show that, the diameter of Au and Ag nanoparticles with a regular shape is about8-10nm, and both of Au/TiO2and Ag/TiO2have a strong absorption in visible region, the absorbing intensity increases with the amount increasing of Au and Ag, due to the Surface Plasmon Resonance (SPR) of noble-metal nanoparticles. The mass fraction of Au, Ag to TiO2have been optimized and0.2%Au/TiO2and2.0%Ag/TiO2exhibited the most excellent photocatalytic activity under visible light irradiation among the samples, Respectively is four times and three times of P25. The ratio of Au(Ag) and TiO2was an important factor for the activity of photocatalyst.Coupling with semiconductor Ag3PO4low band gap and Ag nanoparticle surface plasmon resonance effect in visible light, we prepared visible-light-driven photocatalyst of Ag3PO4/TiO2and Ag/Ag3PO4/TiO2by a chemical reduction and hydrothermal method. The photocatalytic activity were evaluated by degradation of phenol under visible light irradiation. The characterization of SEM. DRS. XRD shows that, Ag/Ag3PO4/TiO2has a uniform size distribution. and diameter is about20nm. Compared with P25and Ag3PO4/TiO2, Ag/Ag3PO4/TiO2exhibited a most strong absorption in visible light area. In phenol degradation experiment, Ag/Ag3PO4/TiO2has the most excellent photocatalytic activity under visible irradiation, and catalytic activity from high to low in turn is Ag/Ag3PO4/TiO2> Ag3PO4/TiO2> P25.The composite of noble metal and TiO2extends the response range of TiO2, making which has a good light absorption in visible area. At the same time, the addition of noble metal enhances the separation of electron-hole pair, and improves the photocatalytic activity of composite catalyst in visible light, making it possible for sunlight’s application in photocatalysis.