Comparative studies of methanol crossover and cell performance for a DMFC

Fuel (methanol) crossover through the polymeric electrolyte membrane in a single direct methanol fuel cell (DMFC) was determined by monitoring the amount of CO2 produced from methanol oxidation. Instead of measuring CO2 from only the cathode by a conventional method, the amounts of CO2 at both of the cathode and the anode were determined in the present study. Gravimetric determination of BaCO3 was employed to accurately analyze the amount of CO2. The equivalent current of methanol crossover can be calculated from the discharge current of the fuel cell and the sum of dry BaCO3 precipitate collected at the anode and the cathode exhausts. The common experimental deviation of measuring methanol crossover caused by CO2 permeation through polymeric electrolyte membrane can be corrected with the proposed method. These data of methanol crossover were compared with the data of single cell polarization behaviors at different methanol concentrations and different temperatures. The energy density of the DMFC is not only dependent on the cell discharge performance but also significantly dependent on the faradaic efficiency that is directly linked to methanol crossover. Under the optimized operating conditions, 1.0 M methanol at 60degreesC, the DMFC has an energy density of 1800 Wh/kg based on pure methanol. (C) 2003 The Electrochemical Society.