Long-term Durability of Pd/a-WO3 and Pd-Pt/a-WO3 Thin Films for Hydrogen Sensors

Optical hydrogen safety sensors based on gasochromic thin films can be used to detect the presence of hydrogen by sensing a change in color of the films upon exposure to hydrogen gas in areas where hydrogen leaks are suspected. In addition to the sensitivity to hydrogen, the long-term durability is an essential requirement for applications of these films in commercially viable hydrogen sensors. In this study, we compared the long-term durabilities of Pd/a-WO3 and Pd-Pt/a-WO3 thin films over a period of 5 months in ambient air. The changes in the optical transmittance of the thin films due to the small polaron transition between W6+ and W5+ ions were monitored as the films were exposed to hydrogen gas and air alternately. We found that the Pd-Pt thin film was an effective catalyst for hydrogen sensors with a better durability than the Pd film.