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Diode-type gas sensors using an anodized TiO 2 film and Pt electrodes modified with Au (Au( n )/Pt/TiO 2 ( n : sputtering time of Au, 0 – 120 (s))) have been fabricated and their H 2 -sensing properties have been investigated in this study. The surface modification of the Pt electrode with Au( n ) drastically improved the H 2 response in dry air. The Au( 20 )/Pt/TiO 2 sensor showed the largest H 2 response in air among all the sensors tested, and the H 2 response in air was close to that in dry N 2 . The H 2 response in air clearly increased with an increase in the humidity, and the H 2 response in wet air was comparable to that in wet N 2 , especially under the higher humidified atmosphere (e.g., absolute humidity: 12.9 g m −3 ). The H 2 responses of all the sensors under every gaseous atmosphere are largely dependent on the applied voltage and operating temperature. In addition, the Au( 20 )/Pt/TiO 2 sensor showed an excellent selectivity against propane and propene. These results indicated that the optimal control of the amount of Au modified on the Pt electrode was quite important in improving both the H 2 response and selectivity in air as well as decreasing the oxygen-concentration dependence of the H 2 response, especially under wet atmosphere.
Hyodo et al. (Tue,) studied this question.