Real-time, in situ measurement of fuel and crossover methanol vapor concentration of a vapor-fed passive direct methanol fuel cell using laser absorption spectroscopy

The concentration of methanol vapor in a vapor-fed direct methanol fuel cell (DMFC) is measured using absorption spectroscopy with a 3.39 μm He-Ne laser. A noise correction method is applied to compensate for the higher noise levels associated with the He-Ne laser. Based on this, realtime, in situ measurement of the methanol vapor concentration has been performed simultaneously in a methanol vapor transport layer and on the cathode surface (air transport layer) under various DMFC operating conditions. The change in methanol vapor concentration and cell performance is measured at various galvanostatic conditions and the impact of methanol concentration in the methanol transport layer on the methanol crossover amount is analyzed. Moreover, the changes of methanol vapor concentration are measured when the fuel supply is suspended during fuel cell operation. No previous method has been able to measure the concentration of the methanol vapor in the methanol transport layer and the air transport layer in real-time with noncontact. The results from this study can contribute to the development of stable and high-power vapor-fed DMFCs.