Exploring the MEMS Enabled Water Preservation in Micro-Scale Direct Methanol Fuel Cells

To ensure the Direct Methanol Fuel Cells (DMFC) achieve a high power density, it is necessary to use high concentration methanol in the storage. However, it is still necessary to supply the needed water in the PEM process. Thus, it becomes necessary to preserve the water from losing at the cathode side. In this exploration, hydrophobic Teflon membrane, with micro-size pores, is applied at the outside of the cathode to prevent water exits to the air stream but still allowing the oxygen to diffuse through. Gold film is sputtered at the inner face of the Teflon membrane to provide electric conductivity. Water tests indicate that this membrane is able to hold significant pressure and allowing the water to be pushed back through PEM to the anode. This modified cathode has been assembled into a micro fuel cell. Electrochemical tests indicated that this fuel cell operates well at various temperatures. Compare with a same fuel cell but using carbon paper instead, it appears that the sputtered gold film has the potential to provide sufficient conductivity. Although the water preservation capability has not been fully validated due to the present micro-scale measurement limitation, this exploration has indicated a promising method to improve the energy density of micro-DMFC.