“Studies on preparation and evaluation of the photocatalytic efficiency of a series of doped Titania”.

Abstract

Heterogeneous photocatalysis has been extensively studied and widely applied to environmental purification both in gas and liquid phases. One of the most studied light-driven materials is Titanium (ΙV) dioxide. Titanium dioxide could be used to decompose organics in aqueous solutions. Chapter (1) includes an introduction on photocatalysis as well as photocatalysts preparations and applications. There are three main approaches are being studied within this research work: (a) Preparation of new TiO2 doped semiconductor photocatalysts using sol-gel hydrothermal method. This method adopted is a good route for the preparation of photocatalyst with high photocatalytic activity. The modification of TiO2 by doping with nitrogen, and (nitrogen & fluorine) has been carried out to increase the spectral sensitivity of TiO2 doped photocatalysts to visible light and to compete with the electron- hole recombination. (b) Preparation of TiO2/CNT’s nanocomposites to improve the photocatalytic activity that is attributed to the enhancement of electron transfer process as well as reduction of electron-hole recombination rate. The enhancement of the interface surface area by preparation of highly conducting arrays of graphitic hexagonal carbon in highly functionalized carbon nanotubes prepared in the laboratory. (c) Preparation of sonicated doped TiO2.The ultrasound treatment has been carried out to create the oxygen vacancies inside the titanium dioxide crystal lattice; such oxygen vacancies will increase the visible light activity, and also minimize the electron hole recombination rate which is a competitive route with the redox reactions. The experimental work of the present thesis has been showed in Chapter (2). The experimental work includes (i) Photocatalysts preparations, (ii) photocatalysts characterization (iii) Photocatalytic activity measurements. In this chapter, the experimental procedure and the different characterization techniques used are presented. Different preparation techniques has been studies these include (i) Chemical Preparation of doped TiO2 and TiO2 nanocomposites , (ii) preparation of metal doped visible-light responsive TiO2 photocatalysts by ultrasound technique (US). The prepared photocatalysts have been well characterized using different techniques such as: (XRD) X-Ray Diffraction Analysis, (BET) Surface Area Measurements, (DRS) diffuse reflectance spectroscopy, (SEM) Scanning Electron Microscopy, (EDX) Energy dispersive X-ray analysis, (HE-TEM) High resolution Transmission Electron Microscopy, (FT-IR) Fourier Transform Infrared Spectroscopy, (TGA) Thermo-gravimetric Analysis and Raman spectroscopy. The photocatalytic activity of the prepared photocatalysts has been evaluated by their ability to degrade some organic pollutants, such as phthalocyanine star polymer, 4-nitrophenol and Methyl violet dye. The results and discussions have been presented in Chapter (3) that is divided into three parts. Part (I) deals with the preparation, characterization and applications of N, N-F TiO2 photocatalysts towards the oxidation of phthalocyanine star polymer. The results show that N, F, −TiO2 prepared by sol-gel hydrothermal method is the most efficient photocatalyst towards the oxidation of phthalocyanine star polymer compared to bare TiO2. The diffuse reflectance (DRS) measurements show that the doping of nitrogen and nitrogen & fluorine into nanocrystalline TiO2 results in an extension of its light absorption into the visible region. The highly enhanced photocatalytic activity of N, F,-TiO2 may be attributed to its higher specific