Hydrogen sensing characteristics of an electrodeposited WO3 thin film gasochromic sensor activated by Pt catalyst

The hydrogen gas sensing performance of platinum (Pt) catalyst activated tungsten trioxide (WO3) thin films were investigated in the present study. The WO3 thin films exhibited a gasochromic effect; i.e., a reversible change in color from transparent when in air to blue when in hydrogen (H-2). All processes proceeded rapidly at room temperature. The films were prepared by the electrodeposition method under ambient conditions. A layer of Pt was then sputtered onto the surface of WO3 film. The cycling of the coloration was obtained from UV-Vis spectra. The Pt catalyst dissociated H-2 into H atoms, which then diffused into the WO3 thin film, which transformed from WO3 to (HxW1-xWxO3)-W-Vt-O-V and changed the color of the WO3 thin film. Therefore, we could detect the existence of H-2 by the coloration of the WO3 thin film. Sensor properties of WO3/Pt films were investigated at room temperature in H-2-N-2 gas mixtures containing 0-50 mol% of H-2. The results show that the transmittance change (Delta T) of the electrodeposited WO3 hydrogen sensor was similar to 2% when the concentration of H-2 was 5 mol%, and similar to 20% when the concentration of H-2 was 50 mol%. Coloration and bleaching had good response and recovery times in the range of 5-60 s, respectively. (C) 2007 Elsevier B.V. All rights reserved.