Improvement of hydrogen gas sensing property of the sol-gel derived Pt/WO₃ thin film by Ti-doping

Platinum nano particles dispersed tungsten trioxide (Pt/WO₃) is a promising hydrogen gas sensor material which can detect it by the change of color. Hydrogen gas sensing properties of Pt/WO₃ thin film strongly depend on its film structure. Particularly, the porosity and the particle size of WO₃ are very important for obtaining good hydrogen sensitivity. The morphology of Pt/WO₃ thin film prepared by solgel process can be modified by the heat-treatment temperature and the Ti-doping to WO₃. Pt/WO₃ thin films consisting of small particles and porous structure were obtained by Ti-doping. Especially, Ti-doping was very effective to obtain the small WO₃ particle in spite of a high temperature heat treatment. It was considered that Ti-doping produced oxygen vacancy in WO₃ lattice and this disturbed the densification of the film and the grain growth of WO₃. This sample showed a good response to hydrogen gas exposure, compared with that of non-doped sample. Therefore, it was found that the surface modification by Ti-doping can enhance the optical hydrogen gas sensing property of Pt/WO₃.