A methanol concentration sensor using twin membrane electrode assemblies operated in pulsed mode for DMFC

A methanol concentration sensor based on twin Nafion membrane electrode assemblies (MEAs) was constructed and characterized by electrochemical methods. Pulsed amperometric detection (PAD) method, using a low frequency (67 mHz) potential waveform of Ered (cathodic activation potential) = −0.2 V, Epre-oxd (anodic pre-oxidation potential) = +0.60 V and Edet (detection potential) = +0.80 V versus DHE with the same pulse width of 5 s was applied to the sensor to enhance its performance. The response in pulsed mode had better linearity over a wider concentration range than that in potentiostatic mode. Furthermore, using this PAD method, the stability of the sensor was enhanced significantly with a slightly linear degradation rate of 2.9 mA h−1 during long-time test. The performances of the sensor in terms of linearity, low anodic saturation and high stability show its potential application for direct methanol fuel cells.