Visible-Light Active Photocatalytic WO<SUB>3</SUB> Films Loaded with Pt Nanoparticles Deposited by Sputtering

Abstract

Visible-Light active photocatalytic tungsten trioxide (WO3) films were deposited at a substrate temperature of 800 degrees C by dc reactive magnetron sputtering using a W metal target. In addition, Platinum (Pt) was deposited on the WO3 film surfaces at room temperature, also by sputtering. In the early stages of Pt growth, formation of Pt nanoparticles could be expected because of the island structure observed in Volmer-Weber-type growth mode. The surface coverage of Pt on the WO3 films was estimated quantitatively by X-ray photoelectron spectroscopy and was found to be approximately 60% after 7 s deposition. High resolution electron microscopy (HREM) demonstrated that Pt nanoparticles with a diameter of about 2.5 nm were generated and dispersed uniformly on the entire surface area of the columnar polycrystalline WO3 films. These Pt-loaded films exhibited high photocatalytic activity in the decomposition of acetaldehyde (CH3CHO) under visible light irradiation.

Visible-light active thin-film WO3 photocatalyst with controlled high-rate deposition by low-damage reactive-gas-flow sputtering

“…The surface coverage of the Pt deposit on the WO 3 surface was analyzed by X-ray photoelectron spectroscopy (XPS, AXIS-ULTRA, KRATOS, Manchester, UK) and the atomic ratios of Pt/(Pt + W) were estimated using the integrated peak areas and atomic sensitive factors of Pt(4f) and W(4f). 10 The deposition rate was estimated as the ratio of film thickness to the deposition time. Film thickness was measured using a surface profiler (Dektak 3, Sloan Tech., Santa Barbara, CA).…”

“…10 Figure 2 presents the photoelectrons emitted from the WO 3 film surfaces upon UV irradiation (4-6 eV). Photoelectron emission at the photon energy of 5.5-6.0 eV decreased with increase in O 2 flow rate during deposition, indicating that the shallow defect energy levels should be the least for the WO 3 films deposited with 100 sccm O 2 flow.…”

“…These coatings are uniform over large areas with very high durability and strong adhesion. [9][10][11][12] However, several important barriers exist for the commercialization of photocatalytic WO 3 films, one of which is the need for a high-rate deposition method for producing high-quality WO 3 films. At present, such materials are fabricated by various deposition methods, the most common of which includes variants of vacuum deposition such as sputtering.…”

“…The deposition rates for the conventional sputtering are approximately 10 nm/min, which is insufficient for practical use. 10 Among the various deposition methods, reactive gas-flow sputtering (GFS) is particularly noteworthy, owing to the high deposition rates achieved. 13,14 Recently, several studies have described the deposition of metal oxide thin films by reactive GFS.…”

“…Pt/WO 3 films deposited by conventional sputtering were previously reported to exhibit high photocatalytic activity towards the decomposition of organic compounds. 10 Pt/WO 3 is believed to promote multi-electron O 2 reduction, with Pt potentially acting as an electron pool and catalyzing O 2 reduction. 3 A GFS system was used for the deposition of 1000-nm-thick WO 3 films on fused silica glass substrates (50 mm × 50 mm) heated to 700…”