ChBE Seminar Series: Y. A. Elabd
Tuesday, October 21, 2008
11:00 a.m.-12:15 p.m.
Room 2110, Chemical and Nuclear Engineering Bldg.
Professor Sheryl Ehrman
Transport Phenomena in Polymer Electrolyte Membrane Fuel Cells
Presented by Y. A. Elabd
Assistant Professor, Department of Chemical and Biological Engineering
Fuel cells, an innovative alternative to current power sources, offer the potential to achieve higher efficiencies with renewable fuels at a lower environmental cost. In particular, the polymer electrolyte membrane (PEM) fuel cell has generated interest for large market applications, such as transportation and portable electronics. A key element in this fuel cell is the PEM, which exchanges protons from the anode to the cathode to derive electrical energy directly from a chemical fuel. However, the PEM is also the component that contributes to significant power losses and low efficiencies. This is due to low proton conductivities at higher temperatures (hydrogen PEM fuel cell) and high fuel crossover rates (methanol PEM fuel cell) in PEMs currently used. For both issues, the transport of molecules and ions in the PEM plays a critical role in the performance of a fuel cell.
Our laboratory has investigated the morphology, transport properties, and fuel cell performance of both ionic block copolymer and ionic blend membranes. In ionic block copolymer membranes, morphology, which was controlled by ion content and membrane formation conditions, has a significant impact on the transport of ions and small molecules. In ionic blend membranes, morphology (phase behavior), which was controlled by blend composition and annealing conditions, has a significant impact on selectivity (proton conductivity/methanol flux). The observed results were in good agreement with fuel cell performance data. In addition to using conventional transport measurement techniques, time-resolved Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy was used to study multicomponent transport phenomena in PEMs on a molecular scale for both the hydrogen and methanol PEM fuel cells. These experimental results will be presented, where the findings provide new insights for future PEM design for improved fuel cell performance.