A methanol sensor for portable direct methanol fuel cells

An aqueous methanol sensor for portable direct methanol fuel cell applications is demonstrated. The design is based on current output limited by methanol diffusion through a Nafion 117 perfluorosulfonic acid membrane. Steady-state polarization measurements demonstrate sensitivity to concentrations of 0 to 4 M over a temperature range of 40 to 80 degrees C. Furthermore, a correlation that is first order in concentration and temperature is demonstrated for concentrations of 0 to 3 M, with an accuracy of +/- 0.1 M. Measurements of transient response to step concentration change indicate a response time of about 10 to 50 s, depending primarily on temperature.