A Methanol Concentration Sensor Using Twin Membrane Electrode Assemblies for Direct Methanol Fuel Cells

Abstract

A methanol concentration sensor based on twin Nafion membrane electrode assemblies (MEAs) was constructed with anodes face to face eliminating the interference of oxygen in environment. The signal of the sensor was obtained by electro-oxidation of the methanol crossing over Nafion membranes from cathodes. During operation, carbon dioxide as a product of methanol oxidation not only was expelled from the gaps between two MEAs, but also permeated across the membranes into the cathodes, which was confirmed by GC in the outflowing stream of the sensor. Electrochemical characterization shows that the sensor has good response performance with a concentration range up to 5M and the signal increases with temperature elevating. The slightly nonlinearity of the working curves was mainly caused by electro-osmotic effect confirmed by electro-osmotic drag coefficient. Though logarithm tendency degradation with 0.9% hr-1 was observed from stability test, the performances in terms of high sensitivity to concentration with wide measuring range and signal recovery characteristics show that the sensor is promising for direct methanol fuel cells.

Keywords

• Fuel cell
• Sensor
• Methanol concentration
• Membrane electrode assembly (MEA)