A passive vapor-feed direct methanol fuel cell (DMFC), which has a membrane vaporizer and a hydrophobic vapor transport layer (VTL), was investigated experimentally to improve its performance when fed with highly concentrated or neat methanol. DMFCs with different structure parameters, such as the VTL thickness, open area ratio of the vaporizer, and thickness of the water management layer, were tested using different methanol concentrations varying from 6 M to neat methanol. The results showed that the performance of the passive vapor-feed DMFC mainly depended on the trade-off between the methanol vapor supply to the anode and methanol crossover through the membrane. Thickening the VTL, or decreasing the open area ratio of the vaporizer, were found to effectively decrease the transport rate of methanol vapor to the anode, leading to an increase in the concentration of the optimum methanol feeding. The hydrophobic water management layer in the cathode was also found to be useful to lower the methanol crossover.

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