(33b) Gas Diffusion Layers in Direct Methanol Fuel Cells (DMFC)

An automated bench-scale fuel cell experimental set-up (PEMFC/DMFC) has been designed and fabricated. The experimental unit is capable of controlling the mass flow rates of gases and liquids, humidity of the inlet gases, as well as the temperature and pressure of the cell in a safe and efficient manner.

The optimum cell temperature and methanol solution concentration are found to be 75°and 4 molar, respectively. The methanol flow rate is found to be 3 mL/min with catalyst loadings on both fabric and paper GDLs of about 2.5 mg/cm2. A study into the effects of PTFE (Teflon") content in both the substrate and microporous layer (MPL), as well as the MPL loading is also conducted. It is found that the anode GDL for a DMFC system should have high PTFE content in the substrate and be coated with a thick MPL with a low PTFE content. From these results a new GDL system, consisting of a paper anode GDL modified with a microporous sublayer and an unmodified paper cathode GDL is developed. The result of this development work is a GDL system which can be manufactured continuously providing improved performance compared to a commercial reference.