Project Title
The effects of hydrophobic gas diffusion media on the performance of a PEM fuel cell
Researcher: John Bedenbaugh
Research Advisor: Dr. John Van Zee
Source: http://www.humboldt.edu/~serc/animation.html
This project will measure fundamental properties of gas diffusion layers (GDL) produced from gas diffusion media (GDM) and will characterize the performance of these GDL during operation of a proton exchange membrane fuel cell (PEMFC). Specifically, two GDM that differ by hydrophobic treatment will be studied to determine optimum operating conditions at both high and low humidity levels. The purpose of this research is to ascertain whether the presence of hydrophobic membranes impacts the performance of a PEMFC.
Two GDM with different treatments are being used. The first type of GDM contains a hydrophobic treatment, while the second GDM is untreated. No relationship between the use of hydrophobic membranes and increased proton diffusion has yet been substantiated in the literature. The goal of this project will be to determine whether such a relationship exists. The long-term goal is to provide a consistent, comprehensive database of these properties and respective GDL performance under a wide range of operating conditions. It is expected that this database can be used to facilitate the development of optimum GDM for PEMFCs.
Introduction of the Problem
In a PEMFC, hydrogen oxidations produce protons and electrons at the anode. The protons diffuse across the membrane at a rate that is dependent upon the degree of hydration of the membrane. As the presence of water increases on the anode side of the membrane, the protons can diffuse at a faster rate, which in turn increases the rate that electrons flow through the circuit from anode to cathode. The protons, after traveling through the membrane, combine with oxygen at the cathode to form water. This process leaves the cathode with an ample supply of water, while the anode remains dry. The purpose of this research is to study a material designed to bring water to the anode side of the membrane.
One way to bring water to the anode is through the use of special coatings of gas diffusion layers (GDL). PEMFCs use GDL to distribute reactants to the anode and cathode at areas that are orthogonal to the bulk flow but parallel to the membrane. The mass transfer limitation depends on the permeability of the gas diffusion media (GDM), which may have hydrophobic or hydrophilic characteristics that interact with fuel cell performance by affecting the degree of hydration of the membrane and water transport across the membrane.
Links
NSF Center for Fuel Cell Research