Green preparation of visible light active titanium dioxide films.
Wellia, Diana Vanda.
Date of Issue2012
School of Chemical and Biomedical Engineering
The thesis focuses on the fabrication of visible light active TiO2-based thin film photocatalyst, via a green method, for self-cleaning and potentially other solar energy harvesting applications. TiO2 is chosen due to its attractive attributes of being inexpensive, nontoxic, photocatalytically active, chemically stable and broad application especially in degrading organic pollutants. However, TiO2 can only be activated under UV light due to the wide band gap of TiO2 (3.2 eV). This limits its widespread applications since ultraviolet is only a small part of solar energy (approximately 4%) and almost non-existent in indoor lighting. Transparent, uniform, crack free and visible light-activated single element doped TiO2 films (N-doped TiO2 and Fe-doped TiO2) were successfully fabricated. The precursors were prepared using a “green” aqueous Peroxo Titanic Acid (PTA) solution approach and coated on the glass substrate using hydrophilicity-assisted method. The optimal photocatalytic activity of the N- doped TiO2 films was about 9.5 and 13.6 times higher than that of un-doped TiO2 coated glass and commercial self-cleaning glass, respectively. The optimal photocatalytic activity of the Fe-doped TiO2 films was about 4 times higher than that of un-doped TiO2. The improvement of photocatalytic activity was mainly due to enhanced visible light absorption by N or Fe doping which is attributed to bandgap narrowing as observed from absorption redshift.