| A direct methanol fuel cell (DMFC) uses methanol solutions as the fuel to generate electricity at near room temperature. Passive DMFCs are promising alternatives to rechargeable batteries as portable power supply systems due to the ease of handling and high theoretical specific energy of methanol (6.1 kWh kg-1). In order to obtain a satisfying performance, dilute methanol solutions (<10 wt%) are typically used as fuel to minimize the methanol crossover through the electrolyte membrane. The specific energy of the fuel cell, however, is significantly decreased by using dilute methanol solutions. To take advantage of the high specific energy of methanol, DMFCs fed with high concentration methanol solutions, including pure methanol, have been investigated.;Both experiments and numerical simulations on thermal and mass transfer in DMFCs have been carried out to prevent severe methanol crossover and achieve stable fuel cell performance. First, water and methanol management systems in DMFCs were studied to understand mass transfer mechanisms. Principles to improve the species management have been suggested. Second, several innovative concepts were proposed, and experimentally tested, to significantly improve the energy density of the fuel cell. Finally, a passive, vapor-feed DMFC fed with pure methanol showed a similar performance to a conventional DMFC using a 10 wt% methanol solution. The calculated specific energy of the DMFC fed with pure methanol, 0.8 kWh (kg fuel)-1, was much higher than the theoretical specific energy of lithium-ion batteries, 0.4 kWh kg -1. |
