SGER: Optimized Catalyst Layer Structure for PEM Fuel Cells

University Of Kansas Center For Research Inc, Lawrence KS

Investigators

Abstract

The catalyst layer, being the power-producing component, is considered as the most important component in a PEM fuel cell. It is a region where all three important phases must be brought together to enable the power generating reactions to occur. Currently, the catalyst layers in a PEM fuel cell are made of platinum on carbon support, Nafion ionomer and Teflon. The solid Pt/C catalyst phase acts as the electro-catalyst for the hydrogen oxidation or oxygen reduction reactions at the anode and cathode and provides electronic conduction to and from the reactive sites. The Nafion ionic phase provides the ionic conductivity or pathways for the protons to migrate to and from the membrane electrolyte and acts as a binder for the catalyst particles. Teflon creates the hydrophobic gas region for reactant gas transport to and from the catalyst surface within the catalyst layers. To achieve high performance in a PEM fuel cell, the three major sources of voltage loss (activation, ohmic and transport) in a PEM fuel cell must be minimized. The voltage loss due to the activation resistance in the catalyst layer can be reduced by increasing the electro-active catalyst surface area. The voltage loss due to the ohmic resistance can be reduced by increasing the ionic and electronic conduction in the catalyst layer. Finally, the voltage loss due mass transport can be reduced by minimizing the thickness of the region through which the slowest transport process occurs (Nafion film) and minimizing the barriers (like liquid water) to the transport processes of reactants to and from the catalyst surface. The intellectual merit of this proposed process is its ability to create a catalyst layer with well-defined and controlled structure necessary to satisfy the requirements needed to achieve high performance in a PEM fuel cell as described above. If this process is successful, it will result in membrane and electrode assemblies and fuel cells with superior performance. The broader impacts of this work are that the use of fuel cells will help reduce environmental problems and the U.S.'s dependence on foreign oil. Consequently, technology that increases its performance will increase its competitiveness and help accelerate the commercialization of this technology. Furthermore, the process developed here could also be used to create ideal catalyst layer structures for electrodes used in other electrochemical applications.