Effects of Surface Modification of Platinum Electrodes with Gold on Hydrogen-Sensing Properties of Diode-Type Sensors

Abstract

Diode-type gas sensors using an anodized TiO2 film and Pt electrodes modified with Au (Au(n)/Pt/TiO2 (n: sputtering time of Au, 0-120 (s))) have been fabricated and their H2-sensing properties have been investigated in this study. The surface modification of the Pt electrode with Au(n) drastically improved the H2 response in dry air. The Au(20)/Pt/TiO2 sensor showed the largest H2 response in air among all the sensors tested, and the H2 response in air was close to that in dry N2. The H2 response in air clearly increased with an increase in the humidity, and the H2 response in wet air was comparable to that in wet N2, especially under the higher humidified atmosphere (e.g., absolute humidity: 12.9 g m−3). The H2 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/TiO2 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 H2 response and selectivity in air as well as decreasing the oxygen-concentration dependence of the H2 response, especially under wet atmosphere.