Temperature dependence and degradation of gasochromic response behavior in hydrogen sensing with Pt/WO3 thin film

The gasochromic characteristics of a sol- gel derived Pt/WO3 film as a hydrogen sensitive material were evaluated at various temperatures using optical transmittance measurements in the near-infrared region. The sensitivity of the film was high and a change of more than 60% in transmittance was observed at room temperature and higher with exposure to a mixture of 4 vol% H-2 and N-2 balance. The response rate was fast and the 90% response time was ca. 10 s at 25 degrees C. However, the recovery rate was slower than that of the response, which suggests that the recovery process may not be a reverse reaction of the response mechanism. As the temperature was lowered, the response became slower and weaker, although a reasonable response was still observed at - 40 degrees C. However, a deterioration of response behavior at - 40 degrees C appeared after the repeated exposure to temperature cycles from - 40 to 100 degrees C. Although the sensitivity and response rate became considerably worse after this exposure, the sensing performance was completely restored by heat treatment at 500 degrees C for 1 h. (C) 2014 Elsevier B. V. All rights reserved.