A mechanism for enhanced photocatalytic activity of nano-size silver particle modified titanium dioxide thin films
Ag-TiO2 nanostructured thin films with silver volume fraction of 0–20% were deposited on silicon and quartz substrates by RF magnetron sputtering and annealed in ambient air at 950°C for 1 h. The phase structure and surface topography of the films were characterized by X-ray diffractometer and transmission electron microscope. Photocatalytic activity of the films was evaluated by light induced degradation of methyl orange (C14H14N3NaO3S) solution using a high pressure mercury lamp as lamp-house. The relation of photocatalytic activity and silver content was studied in detail. It was found that silver content influences phase structure of TiO2 thin films, and silver in the films is metallic Ag (Ag0). With increasing silver content from 0 to 20 vol%, photocatalytic activity of the films increases first and then decreases. A suitable amount (2.5–5 vol%) silver addition can significantly enhance the photocatalytic activity of TiO2 films. The enhanced photocatalytic activity was mainly attributed to the extension of visible light absorption region of the films, the presence of anatase phase, the increase of oxygen anion radicals O2− and reactive center of surface Ti3+, and the better separation between electrons and holes on the films surface.