A model of degradation in a polymer electrolyte membrane
Graduation Date
2009
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Environmental Systems: Environmental Resources Engineering, 2009
Committee Chair Name
Charles Chamberlin
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
PEM, Nafion, Hydrogen fuel cell, Degradation, Humboldt State University -- Theses -- Environmental Resources Engineering
Abstract
A transient model of chemical degradation in a polymer electrolyte membrane (PEM) was developed that uses the hydrogen peroxide and iron (II) concentrations to predict the useful life of the membrane. Experimental values from the literature were used in a second order chemical kinetics rate equation to estimate the rate constant for fluoride production. The fluoride emission rate (FER) has been used as an indicator of peroxide radical induced degradation. The rate equation was combined with the conservation of momentum and species equations in a one-dimensional, through the membrane model. The equations were solved numerically using the Crank-Nicholson method of finite differences programmed in FORTRAN. At each time step the local concentration of reactants and FER was determined and algebraically correlated to the loss of cation exchange sites based on the 'unzipping' mechanism of chemical degradation. The percent degradation of initial exchange sites was used to estimate the useful life of the membrane. In order to meet the industry standard of 40,000 hours of operation, the model results show that the fixed hydrogen peroxide concentration within the membrane should be limited to approximately 340 micromoles per cubic centimeter. Furthermore, the iron (II) concentration was determined to have a strong influence on membrane life, and should be minimized to improve membrane durability.
Recommended Citation
King, C Jordan, "A model of degradation in a polymer electrolyte membrane" (2009). Cal Poly Humboldt theses and projects. 1021.
https://digitalcommons.humboldt.edu/etd/1021
https://scholarworks.calstate.edu/concern/theses/73666683x