During this two-year project, the following steps were followed. Firstly, a comprehensive literature survey was carried to create a list of the alternative membrane electrode assembly (MEA) materials (and their properties) for DMFCs that have superior performance and durability. In addition to the literature survey, the effect of inclusion of zirconium phosphate to the membrane and cathode catalyst on the performance of DMFC was investigated. Secondly, a new FE-DMFC design based on alternative materials was formed and manufactured. This fuel cell was tested under different operating conditions (e.g. membrane type, methanol concentration, and flow rate of sulfuric acid solution). At this stage, multiphysics models (three-dimensional, two-phase model and non-isothermal) of a single FE-DMFC were also developed in Comsol Multiphysics environment. Using these models, the operating and design parameters that yield the highest performance of a DMFC were determined. Thirdly, mathematical modeling of a DMFC stack was performed to investigate the pressure, velocity, and methanol concentration distributions within the stack. Then, this stack model was used as a basis to develop a FE-DMFC stack model in Comsol Multiphysics environment. Finally, a 3D FE-DMFC short-stack model was developed to investigate the effect of key parameters on the performance of the stack as well as to find the methanol concentration and velocity distributions and the pressure drop in the stack. As a result of the research activities carried out during this project, a FE-DMFC having alternative materials was manufactured and it was shown that this fuel cell has much better performance than any previously manufactured FE-DMFCs reported in the literature. It was also shown experimentally that a FE-DMFC can reduce the methanol crossover considerably. The design and operating parameters that increase the performance of this fuel cell mostly were also identified. The main results achieved are listed below.
• High faradaic efficiencies up to 98 % are possible with the FE-DMFC at different current densities.
• Under the tested conditions, methanol crossover can be reduced by a factor of more than 10.
• Nafion® 115 based FE-DMFC has the best performance (0.38 V at 0.1 A/cm2) when it operates with 1 M methanol concentration and 5 ml/min sulfuric acid flow rate.
• The numerical studies showed that flowing electrolyte thickness, flowing electrolyte flow rate and methanol concentration are the most important parameters affecting the performance of the FE-DMFC.
• In a FE-DMFC stack, the cells furthest from the outlet manifold in a U-shaped configuration have the least amount of flow. This lead the anode methanol concentration distribution to have a low uniformity in these cells.
As a result of the activities carried out during this project, three journal papers and three conference papers were prepared. Five presentations were done in international conferences; and two seminars were given. Dr. Colpan created a webpage for the project, which included the objective, research highlights, and a list of the presentations and publications done from this project.
