Cell voltage transients of a gas-fed direct methanol fuel cell

The cell voltage behavior of a direct methanol fuel cell (DMFC) was investigated in response to the dynamic change of the cell current (current steps with rise/decay time=1 ms). The cell voltage was measured on a complete cell under regular fuel cell working conditions. To minimize the methanol cross-over from the anode to the cathode and its influence on the dynamic cell behavior, the anode feed of the DMFC was kept gaseous. The cell voltage transient permits a differentiation of three influencing effects on the cell dynamic: (1) the double layer capacity and the charge transfer resistance of the anode and the cathode, (2) the CH3OH dehydrogenation products poisoning of and its removal from the anode catalyst surface and (3) the impact of the remaining methanol cross-over. Contrary to the first two effects, which take place in the time range of 50 ms to 1 s, the methanol cross-over influences the cell voltage for approximately 10 s after the current changes.