Hydrogen sensing performance and stability of WO3–SiO2 composite film doped with Pt catalyst

Abstract

Hydrogen energy has attracted attention as a new energy carrier because it does not generate CO2 emissions during combustion. However, numerous problems face the establishment of a hydrogen infrastructure society. One problem is safety when using hydrogen. A fast sensing system for hydrogen at low concentrations will be needed for hydrogen to be used safely. WO3 is expected to be used as an optical hydrogen sensor element because it reacts with hydrogen and changes color. We prepared Pt-doped WO3 films by the sol–gel method using an ion-exchange technique under various experimental conditions and investigated the films’ response properties to hydrogen and their morphology. As a result, a Pt/WO3 film with SiO2 (Pt/WO3–SiO2 film) annealed at 200 °C showed the shortest coloring and bleaching time to 4 vol% hydrogen. The films also showed good reproducibility with respect to their hydrogen response and good long-term stability. In addition, the fast bleaching time led to a stable repeated response, enabling the films to be used in real-time monitoring applications. Moreover, the sensitivity of the Pt/WO3–SiO2 films depended on the hydrogen concentration, which suggested that quantitative sensing of hydrogen at concentrations below the lower explosive limit could be realized. Furthermore, the catalyst Pt active state and the difference in gas diffusivity due to the microstructure of the films were considered through analysis of the surface, cross-sectional structure, and elemental state of the films. Graphical Abstract