Photocatalytic activity of TiO2 thin films by hydrogen DC plasma

Thin layers of anatase titanium dioxide were coated on glass by spray pyrolysis method. The layers were hydrogenated by DC plasma from room temperature up to 350 °C. Hydrogen plasma treatment at low temperatures, leads to decrease the surface roughness, while surface roughness is increased by enhancing plasma temperature. Layers' band gap was decreased 0.13 eV by plasma treatment at highest temperature. Hydrophilicity and photocatalytic properties of the layers under plasma treatment at 150 and 200 °C, were improved noticeably. However, plasma treatment at temperatures above 200 °C was lead to decrease hydrophilicity and photocatalytic activity of TiO2 layers. The reason seems formation of oxygen vacancies in the interior layers that act as charge carriers' recombination centers.