Effect of nitrogen on the photocatalytic activity of TiOxNy thin films

Abstract

Visible light active nitrogen doped titanium oxide (TiOxNy) thin films were deposited by dc reactive magnetron sputtering on glass substrates at different nitrogen flow rates and sputtering pressures. All the deposited films consist of composite of TiOxNy and TiO2 phases of anatase and a small portion of the rutile (R) phase was embedded in the polycrystalline films. X-ray diffraction and optical studies confirmed that the prepared films had nitrogen substituted at some of the oxygen sites in TiO2, which formed narrow N 2p band above the valence band. The surface roughness of the films varied between 5 and 25 nm for the films deposited at nitrogen flow of 0.5–5 SCCM (standard cubic centimeter per minute), respectively. The photocatalytic decomposition of methanol was investigated using fourier transform infrared as a function of irradiation time. The formaldehyde and CO species are the main intermediates by increasing the irradiation time in the presence of pure methanol and CO2 is produced after the complete decomposition. The properties of the films, including the crystallinity, surface morphology, and light absorption capability, are influenced by the nitrogen flow rate while the photocatalytic reaction on TiOxNy thin films is very sensitive to oxygen vacancy and its surface structure.