Seminars Archive

Hydrogen doping in Titanium dioxide thin films.

Abstract
One of the limitations of titanium dioxide (TiO2), a photocatalyst with the most applications, is its wide band gap. Lots of efforts have been made to reduce the band gap of TiO2 to use wide range of solar spectrum as a renewable energy source. Recently, hydrogen doping has created remarkable effects in the photocatalytic activity of bulk-TiO2 [Chen et al., Science 331 (2011) 746]. We have used spray pyrolysis to coat the TiO2 thin films on glass substrate. Then the prepared TiO2 thin films were exposed to the heat-treated dc hydrogen plasma. The prepared TiO2 thin films, before and after hydrogenation, were studied under different experiments; UVvisible spectroscopy, angle survey, atomic force microscopy, X-ray diffraction, infrared spectroscopy, and thickness tests. Increasing the plasma temperature from room temperature up to 350°C leads to the shift of absorption edge to the visible range at most 13 nm (0.15 eV). The obtained results show that applying plasma in the low temperatures range less than 250°C, leads to the decrease of roughness and improves the hydrophilicity and photocatalytic activity of thin films. Increasing the plasma temperature up to 350°C causes the destructive effects which are the results of hydrogen ion saturation and creation of oxygen vacancies, i.e. electron and hole recombination centers.