Thesis (M.Eng.)--Chulalongkorn University, 2010

Titanium dioxide was doped with boron in order to improve its photocatalytic activity for water splitting in the visible light region. Titania was synthesized via a sol-gel method and boron was added to the sol in the amount ranging from 0 to 2%(w/w). Then magnesium was added to the boron-doped titania in the amount of 1%(w/w). The catalysts were fired at 350 ℃ for two hours. The catalysts were characterized by UV-visible diffuse reflectance spectroscopy, X-ray diffractometry, nitrogen physisorption, scanning electron microscopy, fourier transform Infrared (FT-IR), and photoluminescence. The photocatalytic activities of boron-doped catalysts were evaluated for the splitting of water under both ultraviolet light and visible light (wavelength > 420 nm) irradiations for the duration of five hours. Methanol was added to act as a sacrificial agent at the volume ratio of water to methanol of 4 to 1. The photocatalytic activity of co-doped TiO₂ increased under UV irradiation as the boron loading increased because of better absorption in the visible region and slower recombination of photogenerated charge carriers. Under visible irradiation, the highest photocatalytic activity was obtained by the catalyst that contained 1% (w/w) B and 1% (w/w) Mg. This was attributed to the role of carbonaceous species sensitizer as a visible light.