Photocatalytic properties of TiO2/WO3 bilayers deposited by reactive sputtering

To study the decomposition of methyl alcohol (CH(3)OH) by a photocatalytic reaction, TiO(2)/WO(3) bilayers composed of TiO(2) and WO(3) films were deposited using reactive sputtering at the working gas pressure P(W) of 1 and 3 - 8 mTorr, respectively. The optical transmittance spectra of as-deposited TiO(2)/WO(3) bilayers monotonically decreased with decreasing wavelength in the range of 200-900 nm. When depositing WO(3) films, the adsorption edge shifted to a higher wavelength of about 400 nm with decreasing P(W). These spectra may depend on the properties of WO(3) films, rather than those of TiO(2) films. As expected, the bilayer can adsorb much more visible light compared to TiO(2) single layers. From the measurement of Fourier transform infrared transmittance spectra, CH(3)OH can be decomposed strongly into CO(2) and H(2)O molecules, compared to the TiO(2) single layer. When the TiO(2)/WO(3) bilayer was irradiated with artificial sunrays for 130 min, the formation rate of CO(2) molecules was about two times as fast as that in the Ti02 single layer. We found that the decomposition of CH(3)OH may depend on the crystallinity and optical properties of WO(3) underlayers. (C) 2003 American Vacuum Society.