High Temperature MEA Development for PEM Fuel CellsAndDevelopment of Educational Tools for PEM Fuel Cells

Dr. James Fenton
Friday, November 18, 2005
1:30PM - ENG II 102

Abstract


Innovative proton exchange membrane-electrode assemblies (MEAs) that provide excellent ionic conductivity and good performance in an under-saturated environment (120 oC, 1 atm., 35%RH and 70 oC, 1 atm., dry) have been developed. These MEAs are currently being evaluated for various fuel cell applications which operate on hydrogen fuel containing carbon monoxide or on pure hydrogen in the absence of reactant humidification. The favorable MEA properties are obtained by the incorporation of solid proton conductors, such as phosphotungstic acid or zirconium hydrogen phosphate, into the NafionÒ ionomeric electrolyte to provide protonic conductivity at reduced water vapor pressure and assist in water retention.

The design of improved membrane electrode assemblies (MEAs) requires an understanding of the different sources of overpotential that arise during fuel cell operation, namely activation overpotential, ohmic overpotentials and transport overpotentials. Knowing the relative contributions of each source to the overall overpotential permits a proper focus of experimental efforts. The trends shown by different overpotential sources with temperature and humidity are equally important in the design of MEAs operating at undersaturated conditions, and for start up and shut down analyses. A rational approach to deconvolute polarization data into activation, ohmic and transport related components will be presented.

The determination of fuel (H2 and methanol) crossover and electrochemical surface area via voltammetric techniques will be demonstrated. Two techniques to obtain the electrolyte resistance, namely AC impedance spectroscopy and current interruption will be discussed, and a comparison made between the results obtained using these techniques at different temperatures and humidities on the same MEA. The determination of the effect of temperature and humidity on carbon monoxide tolerance of the anode electrocatalyst will be presented. Finally, experimental determination of the effect of reactant partial pressure, operating temperature and relative humidity on the different overpotential sources will be discussed.

Short Bio


His major research interests are in fuel cells, sustainable energy, electrochemical engineering, environmental engineering and pollution prevention. His teaching interests are in unit operations for chemical and environmental engineering (both lecture and laboratory courses), fluid, heat and mass transfer, electrochemical, fuel cell engineering (combined lecture and laboratory course), freshman engineering and industrial ecology. He is most proud of his role in the professional development of his graduate students. Together they have authored more than 100 seminars at national/international meetings. He has edited eight Electrochemical Society Conference Proceedings, given over 200 seminars and chaired over 50 symposia. He was honored to be nominated as a candidate for the Vice-President of the Electrochemical Society.

Ongoing fuel cell research and education topics include: methanal oxidation electrocatalysts, CO tolerance electrocatalysts, hydrogen purification processes, low methanol corssover membranes, high temperature membranes, membranes needing no external humidification, selective oxidation catalysts, gas diffusion layer design, reversible PEM fuel cells, biomass and landfill gas fuel processing, undergraduate laboratory fuel cell experiments, K-12 fuel cell demonstrations and experiments and design of PEM FC powered toys.

Work is continuing in the development of high-temperature membrane-electrode assemblies (MEAs) for proton-exchange membrane fuel cell (PEMFC) applications. Two patents for this technology are in place and several are in process. The membrane is a composite of polytetrafluoroethylene (PTFE), Nafion®, and phosphotungstic acid. The MEA is the key component of the PEMFC, making up a substantial fraction of the fuel cell power plant cost. The unique feature of our MEA is its ability to operate at higher temperatures and under drier environments than the present commercial membranes. This ability can result in higher fuel cell system efficiency and lower cost. Higher temperature operation allows the use of smaller radiators in automobiles and more useful waste heat for stationary applications. In contrast with commercial MEAs, our MEA can be used under dry reactant feed conditions for portable applications.

Dr. Fenton's Bio