Development and characterization of a silicon-based micro direct methanol fuel cell

A silicon-based micro direct methanol fuel cell (μDMFC) for portable applications has been developed and its electrochemical characterization carried out in this study. Anode and cathode flowfields with channel and rib width of 750 μm and channel depth of 400 μm were fabricated on Si wafers using the microelectromechanical system (MEMS) technology. A membrane-electrode assembly (MEA) was specially fabricated to mitigate methanol crossover. This MEA features a modified anode backing structure in which a compact microporous layer is added to create an additional barrier to methanol transport thereby reducing the rate of methanol crossing over the polymer membrane. The cell with the active area of 1.625 cm² was assembled by sandwiching the MEA between two micro-fabricated Si wafers. Extensive cell polarization testing demonstrated a maximum power density of 50 mW/cm² using 2 M methanol feed at 60°C. When the cell was operated at room temperature, the maximum power density was shown to be about 16 mW/cm² with both 2 and 4 M methanol feed. It was further found that the present μDMFC still produced reasonable performance under 8M methanol solution at room temperature.