AVS 56th International Symposium & Exhibition
    Advanced Surface Engineering Monday Sessions
       Session SE1-MoM

Paper SE1-MoM8
Enhancement of Visible-Light Activities of Photocatalytic WO3 Films Deposited by Sputtering

Monday, November 9, 2009, 10:40 am, Room B1

Session: Photocatalytic Coatings
Presenter: A. Murata, Aoyama Gakuin University, Japan
Authors: A. Murata, Aoyama Gakuin University, Japan
M. Kikuchi, Aoyama Gakuin University, Japan
N. Oka, Aoyama Gakuin University, Japan
Y. Sato, Aoyama Gakuin University, Japan
S. Nakamura, Aoyama Gakuin University, Japan
H. Yamaguchi, Aoyama Gakuin University, Japan
Y. Shigesato, Aoyama Gakuin University, Japan
Correspondent: Click to Email
We have been reported on photoinduced superhydrophilicity and oxidative decomposition of organic compounds under visible light irradiation on polycrystalline WO3 films deposited by reactive magnetron sputtering at the substrate temperature at 800 oC [1,2,3]. On the other hand, Abe, et al. reported that WO3 powder loaded with Pt nanoparticles exhibits high efficiency for the decomposition of organic compounds under visible light irradiation, certainly due to promotion of multielectron O2 reduction [4].

In this study, we deposited the photocatalytic WO3 films with visible-light-activity on fused silica glass substrates by dc reactive magnetron sputtering using a W metal target. The substrate temperatures and total gas pressure during the deposition were 800 oC and 5.0 Pa, respectively. In addition, Pt was deposited on WO3 film surfaces at RT by sputtering with various sputtering power and deposition time. In the case of Pt deposited on WO3 films, 3D growth mode (Volmer-Weber) should be expected in general, because atoms or molecules in the deposit are more strongly bound to each other than to the substrate. The surface coverage of Pt on the WO3 films were estimated by X-ray photoelectron spectroscopy (XPS), which implied that the Pt film followed Volmer-Weber type film growth process, i.e., after an initial nucleation, an island structure grew and coalesced with each other with increasing film thickness. High resolution electron microscopy (HREM) revealed that Pt nano-particles with diameter of about 2 nm were generated at the early stages of the Pt film growth, which dispersed uniformly on the columnar polycrystalline WO3 films possessed of large surface area.

The photocatalytic activity was evaluated by photodecomposition of acetaldehyde under the irradiation of visible light (Xe lamp with a 410-500 nm band pass filter, 1.0 mW/cm2). With increasing in the Pt deposition time upto 10 sec, the decomposition rates for the Pt loaded WO3 films were higher than that on the pristine WO3 film. Especially, for the WO3 films deposited with the Pt by 7 sec, acetaldehyde was completely decomposed within 150 min, on which the surface coverage of Pt indicated about 60%.

[1] M.Ebihara, Y.Shigesato,et al., Proceedings of the 3rd ICCG (2000) 137.

[2] M. Kikuchi, Y. Shigesato, et al., Abstract of the 21st IUPAC SYMPOSIUM (2006) 496.

[3] M. Kikuchi, Y. Shigesato, et al., Proceedings of the 6th ICCG (2006) .

[4] R. Abe, B. Ohtani, et al., J. Am. Chem. Soc. 130, (2008) 7780.