Preparation And Photocatalytic Performance Of Iodine/Nitrogen/Carbon Doped One-dimensional Ti_O2-based Photocatalysts

Photocatalytic technology is one of the most important Advanced Oxidation Process (AOPs) by using light irradiation to photo-degradate organic pollutions. Photocatalytic technology plays an essential role in the control of environmental pollution. Titanium dioxide (TiO2)-based photocatalys are very siginificate for the photo-degradation of organic pollutions in water treatment, since its exclent ultra-violet photocatalytic properties. However, the main drawbacks of (TiO2)-based photocatalys are the high combination rate of photo-induced charge carrers and its limitation of ultra-violet excitation (3-5%among the whole solar spectra). Solutions from the theory and application to Titanium dioxide (TiO2)-based photocatalyst materials are given priority to in their visible light catalytic properties and increasing light catalytic efficiency, in order to realize the green development of photocatalysts, as the current international research frontiers and hot spots. This thesis reported the doping/modification of titanium dioxide photocatalyst via hydrothermal synthesis process and heat treatment. Chemical reactions and the catalytic mechanisms were detailed studied and reported, and through the research we were expected to gain the following research results.We reported in this thesis the traditional hydrothermal synthsis process of one-dimensinal TiO2nanowires (TiO2NWs) for UV photocatalytic properties. The as-prepared1D TiO2NWs showed remarkable UV activated performance under the photo-degradation of10mg L-1(0.03mM) Methylene blue (MB) solution, with the apprate degradation rate constant Kap value of0.05-0.06min-1, which close to the value of commercial Degussa P25with value of0.065min-1. The photocatalytic degradation efficiency under UV light (λ=365nm) followed a pseudo first-order kinetic model. Experiments on this preliminary study confirmed that TiO2NWs photocatalysts worked well under ultraviolet excitation, which theoretically enable us to obtain visible-activited TiO2catalysts by means of doping or modification.We reported in this research the modification/co-doping of C/N-TiO2photocatalysts. C-TiO2photocatalysts showed enhanced solar spectrum absorption, and surface modification mechanism was verified-carbon oxide film was coated on the surface of TiO2nanowires; In co-doped C/N-TiO2system, N2in the reaction system helped to generate free C atoms, which replaced O in TiO2lattice to form C-Ti-O chemical bonds, co-doping mechanism enhanced the ultraviolet excitation property of modified C/N-TiO2, with maximum of Kap reached 0.163min-1.A facile and efficient way of generating oxygen vacancies in visible-activated one-dimensional iodine doped TiO2photocatalysts was first reported in Chapter4. A two-step hydrothermal synthesis approach was used to synthesize TiO2nanomaterials modified by iodic acid (HIO3) as a dopant. Rutile nanowires using a two-step synthesis method produced the highest methylene blue (10mg L-1) degradation rate constant, Kap, of7.92×10-3min-1under visible light irradiation (λ>400nm), which was an order of magnitude greater than commercial P25(3.87×10-4min-1) and pristine TiO2nanowires (4.18×10-4min-1). Detailed analysis was conducted to illustrate the intrinsic doping/reaction mechanisms of iodic acid in the modification of the TiO2matrix. The generation of oxygen vacancies and the formation of I-O-Ti bonds in the TiO2lattice were analyzied. Multi-valences of iodine facilitated the generation of oxygen vacancies and3d state Ti3+species in the TiO2lattice. The visible light absorption and enhanced photocatalytic activity of the TiO2nanomaterials were attributed to iodine multi-valences in I-O-Ti bonds, the concentration disparities between oxygen vacancies and3d state Ti3+sites in the TiO2lattice.In the research1D I/N-TiO2was prepared and characterized, part of N atoms substituted O to form N-Ti-O into TiO2crystal lattice, Iodine was formed on the surface of TiO2by surface modification. Electrophoresis deposition method was adapted in the fabrication of1D TiO2membranes with smooth surface. Self-assembly membrane photocatalytic reaction device was designed and tested Anatase type membrane catalytic materials under ultraviolet light showed photocatalysis reaction rate constants values of Kap about0.04min-1.