Title: Modeling proton-exchange-membrane fuel cell performance/degradation tradeoffs with chemical scavengers

Abstract

One of the primary limiting factors for proton-exchange-membrane (PEM) fuel-cell lifetime is membrane degradation driven by operational stressors such as generation of highly reactive radical species, which result in cell failure and voltage decay. To extend the lifetime of the membrane, cerium ions are added to the membrane to mitigate the effects of chemical degradation by scavenging radicals produced by crossover of reactant gases across the PEM. Although cerium has shown to be very effective at reducing chemical degradation during PEM fuel cell operation, the cerium ions also lead to a decrease in performance due to changes in the membrane transport properties and possible site blockage in the catalyst layers. In this paper, a full-cell, transient performance and durability model is presented in which a micro-kinetic framework accounts for gas crossover induced degradation and concentrated-solution theory describes transport in the PEM. The transport model takes into account the coupled nature of the electrochemical driving forces that cause transport of cerium ions, protons, and water. The cell model predicts the migration of cerium out of the membrane and into the catalyst layers and its impact on performance. A comparison between dilute-solution-theory and concentrated-solution-theory models shows how water management in the cellmore » also effects cerium distribution, where higher relative humidity leads to better retention of cerium in the membrane. A voltage loss breakdown shows that cerium leads to performance losses in the cell both by decreasing proton activity and by modifying transport properties of water and protons through the membrane. Transient simulations show that the optimal tradeoff between performance and durability metrics is reached at low cerium concentrations in the membrane (less than 1% of membrane sulfonic acid sites occupied by cerium for our analysis). Finally, analysis of membrane thickness and catalyst layer thickness as design parameters shows that thicker membranes and thinner catalyst layers best optimize both performance and durability.« less

Authors:

Ehlinger, Victoria M. ;

• Search DOE PAGES for author "Ehlinger, Victoria M."
• Search DOE PAGES for ORCID "0000-0001-7333-1271"

Crothers, Andrew R. ;

• Search DOE PAGES for author "Crothers, Andrew R."
• Search DOE PAGES for ORCID "0000-0003-4466-1057"

Kusoglu, Ahmet ;

• Search DOE PAGES for author "Kusoglu, Ahmet"
• Search DOE PAGES for ORCID "0000-0002-2761-1050"

Weber, Adam Z.

• Search DOE PAGES for author "Weber, Adam Z."
• Search DOE PAGES for ORCID "0000-0002-7749-1624"

Publication Date:

Thu Oct 01 00:00:00 EDT 2020

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office

OSTI Identifier:

1698274

Alternate Identifier(s):

OSTI ID: 1713243

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

JPhys Energy

Additional Journal Information:

Journal Name: JPhys Energy Journal Volume: 2 Journal Issue: 4; Journal ID: ISSN 2515-7655

Publisher:

IOP Publishing

Country of Publication:

United Kingdom

Language:

English

Subject:

25 ENERGY STORAGE; fuel cell; modeling; durability; degradation; mitigation; cerium