Low-temperature chemical fabrication of Pt-WO3 gasochromic switchable films using UV irradiation

Abstract

Gasochromic films can reversibly switch their optical transmittance upon alternating exposure to diluted H2 and O2 gases. These films are usually prepared by physical methods such as sputtering and pulsed-laser deposition. Here, we report a new method using UV irradiation for low-temperature chemical fabrication of Pt-WO3 gasochromic switchable films. In this method, an amorphous film of WO3 is produced, and the photocatalytic properties of the WO3 are utilized for the reduction of the Pt2+ precursor to Pt particles. This method also generates a large number of voids in the film at 100°C. The initial transmittance of the Pt-WO3 films was extremely high (approximately 80%) over the visible to the near infrared region, and the optical change in the transmittance upon exposure to H2 gas or air was large (approximately 70% at a wavelength of 670nm). In addition, the switching time of the films was as fast as 5s, and the switching durability of the films was preserved for over 1500 cycles.