Microfabricated Fuel Cells with Thin-Film Silicon Dioxide Proton Exchange Membranes

Microfabricated fuel cells have been designed and constructed on silicon integrated circuit wafers using many processes common in integrated circuit fabrication, including sputtering, polymer spin coating, reactive ion etching, and photolithography. Proton exchange membranes (PEMs) for an "integrated" fuel cell have been made by low-temperature, plasma-enhanced chemical vapor deposition of silicon dioxide. Fuel delivery channels were made through the use of a patterned sacrificial polymer below the PEM and anode catalyst. Platinum-ruthenium catalyst was deposited by dc sputtering. The resistivity of the oxide films was higher than traditional polymer electrolyte membranes, e.g., Nafion, but they were also much thinner. Thus, the "area-resistance" (product of resistivity times thickness) was similar. Fuel cell performance shows that the amount of catalyst in the thin-film electrodes chiefly limits the performance. Steady-state power densities of at 0.3 V were achieved for a double-layer sputtered anode catalyst device with hydrogen fuel at room temperature.