A passive direct methanol fuel cell (DMFC) with its cathode current collector made of porous metal foam was investigated experimentally. The measured polarization curves showed that the passive DMFC having the porous current collector yielded much higher voltages than did the cell having the conventional perforated-plate current collector under the high methanol concentration operation. It was further demonstrated that the improved performance for the porous current collector was attributed to (i) the enhanced oxygen transport on the cathode as a result of a larger specific transport area, (ii) the increased operating temperature as a result of the lower effective thermal conductivity of the porous structure, and (iii) the faster water removal as a result of the capillary action in the porous structure. In particular, the constant-current discharging tests showed that the passive DMFC with the porous current collector not only yielded much high voltages but also offered much more stable operation. It was also shown that the significant improvement on the operation stability was attributed to the fact that the capillary force in the porous current collector can reduce the liquid water accumulation on the cathode.

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