As next-generation portable electronic equipment continues to shrink in size and increase in capabilities, high energy density direct methanol fuel cells (DMFCs) have become an attractive option to meet the additional power demands. While promising, DMFC development has been limited by issues related to the polymer electrolyte membrane which separates the anodic and cathodic compartments. Polymer electrolyte membranes must be kept hydrated to facilitate proton transport, i.e. water management, and permeation of methanol through the Nafion membrane, i.e. methanol crossover, results in mixed potentials at the cathode.

To eliminate the membrane constraints of a DMFC, we have previously designed a direct methanol laminar flow fuel cell (LFFC) that replaces a polymer electrolyte membrane with liquid-liquid contact between a fuel and electrolyte stream. This liquid-liquid contact limits methanol crossover to diffusion, but still allows a large area for potential methanol crossover. In order to inhibit methanol crossover in currently-designed LFFCs, the fuel concentration boundary layer must be pressed close to the wall via high flow rates or more commonly, wide channels. In an effort to maintain small electrode-to-electrode distances, for less volume and higher specific energy, we have placed a nanoporous polymer at the liquid-liquid interface of a methanol LFFC. This so-called separator greatly minimizes the total area of the fuel-electrolyte interface, and hence, the area in which unreacted methanol molecules can crossover to the cathode.

In this presentation, we will compare the performance a methanol LFFC with and without a separator. Electrochemical impedance spectroscopy (EIS) data will be used to characterize the separator's added resistance to charge transfer and the separator's ability to decrease methanol crossover while still maintaining small electrode-to-electrode distances.