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

A methanol sensor for direct methanol fuel cell (DMFC) is required. A shear horizontal surface acoustic wave (SH-SAW) sensor for electrical property determination is applied for this purpose. The operating temperature of DMFC is above 50 °C. The wave propagation characteristics were calculated while considering temperature coefficient. The results indicate that the sensitivity increases with increasing temperature. Then, the concentrations of methanol solutions were measured using the SH-SAW sensor. Measured temperature ranged from 25 °C to 60 °C and concentration ranged from 0 to 50% by weight. Linear relationships between the sensor response and concentration were obtained. An increase in the sensitivity is experimentally confirmed. The limit of the detection was estimated from experimental results to be 0.1% by weight. Because formic acid is produced in the DMFC electrode reaction, its effect was discussed. The concentrations of mixture solutions of methanol and formic acid were measured. Using a chemometric method, we succeeded in determining the concentrations of both, simultaneously. Therefore, the SH-SAW sensor can be possibly used for DMFC.