Mass spectroscopy for the anode gas layer in a semi-passive direct methanol fuel cell using porous carbon plate: Part II. Relationship between the reaction products and the methanol and water vapor pressures

Subsequent to Part I, in situ mass spectrometry using a capillary probe was conducted in order to evaluate the gas condition of the anode gas layer of a semi-passive direct methanol fuel cell (DMFC) employing a porous carbon plate (PCP). Different types of PCPs were used for the DMFC, and the production of intermediates besides CO2, i.e., methylformate (HCOOCH3), formaldehyde (HCHO) and formic acid (HCOOH), were investigated. The profiles of the vapor pressures of these products were related to the vapor pressure of methanol and water in the gas layer. The production rate of each intermediate was formulated as a power function of the methanol and water vapor pressure ratio, PCH3OH/PH2OPCH3OH/PH2O, with the power factors of 2.07, 0.47 and −0.57 for methylformate, formaldehyde and formic acid, respectively. Based on these equations of the production rates, the product distribution could be quantitatively estimated.