Photocatalytic cementitious material for self-cleaning and anti-microbial application

In recent years, titanium dioxide (TiO2) has become the most popular photocatalyst for environmental purification due to its capability to completely degrade a large variety of organic pollutants. However, an attempt to widen the scope of TiO2 application is hindered due to wide bandgap of TiO2 that limits the photoactivation of TiO2 only under UV irradiation. In addition, previous work on environmental purification usually employed TiO2 in the form of suspension system for water treatment. Although TiO2 suspension system provides high surface area for photocatalytic reaction and can minimize mass transfer limitation, the widespread use of TiO2 is restricted as suspension system has additional separation problems. This study therefore focused on (1) developing visible light activated TiO2-based photocatalyst for enhanced degradation of organic pollutants under visible light irradiation and (2) immobilization of TiO2 composite on cementitious materials as supporting media for self-cleaning and antimicrobial application. The first part of this study was the synthesis of visible light activated graphene based TiO2 composites by a one-step hydrothermal process. It was found that the combination of GO and TiO2 exhibited a significant improvement in degradation of methylene blue compared to unmodified TiO2. GO-TiO2 displayed an obvious redshift in the absorption edge to higher wavelength region along with strong absorption in the visible light range. Under visible light irradiation, graphene acts as sensitizers to absorb photon. Following absorption, the excited graphene injects electrons into the conduction band of TiO2; thus, the created electron-hole pairs become well-separated. These processes could significantly suppress the charge recombination and finally increase the photocatalytic activity. On the other hand, the enhancement of adsorption capability also contributes to the increase of photocatalytic activity. This finding is of considerable importance since it suggests that the simple synthesis process still provide remarkable improvement in the photocatalytic activity. In following research, the synthesized catalyst particles will be dispersed in cementitious materials to formulate functional cementitious coating. Finally, their photocatalytic performance in self-cleaning and anti-microbial application will be evaluated.Doctor of Philosoph