Development of methanol sensor for direct methanol fuel cells using a shear horizontal surface acoustic wave

Abstract

A liquid-phase sensor is realized by using a shear horizontal surface acoustic wave (SH-SAW). In this paper, methanol (MeOH) sensor using the SH-SAW is discussed. A direct methanol fuel cell (DMFC) produces electric power. Generation efficiency of the DMFC strongly depends on the MeOH concentration. Therefore, MeOH sensor is required. As formic acid is produced during the electrode reaction of the DMFC, first, the influence of it to the SH-SAW sensor is cleared by immersion test. Maximum operating temperature of the DMFC is 80°C. Minimum temperature depends on a place of installation. In this paper, it is assumed −5°C. The SH-SAW sensor must detect MeOH concentration from −5 to 80°C without malfunction. The results indicate that the MeOH concentration is able to measure when temperature is lower than 60°C. If temperature is higher than 60°C, bubbles are generated on the sensor surface and the sensor is influenced by them. This is new problem for developing SH-SAW MeOH sensor. Also, optimum SH-SAW sensor frequency is discussed.