Development of a 150-watt direct methanol fuel cell system

Stack development for a Nafion(R) based 150-watt direct methanol fuel cell (DMFC) system is discussed in this paper. Single cell data for a membrane electrode assembly (MEA) that can operate at low air stoichiometry is presented. The stack operating conditions for achieving a water balance have been determined to be 55/spl deg/C 0.5 M MeOH at a maximum of 1.75 times air stoichiometry at 100 mA/cm/sup 2/. Single cells with a 25-cm/sup 2/ active area have been operated in this regime and can maintain an average cell voltage of 0.43 V at 100 mA/cm/sup 2/ for 120 minutes with a cell voltage decay of 0.2 mV/min. A five-cell stack with a 80-cm/sup 2/ active area, scaled up from the single cell, was capable of sustaining 100-mA/cm/sup 2/ load at a 1.75 air stoichiometry for over 70 hours, with a voltage decay of the order of 2 mV/hr. Voltage decay is reversible by purging excess water in the cathode.