Electrochemical Characterization of Evolving Ionomer/Electrocatalyst Interactions Throughout Accelerated Stress Tests

Leiming Hu, Tim Van Cleve, Haoran Yu, Jae Park, Nancy Kariuki, A. Kropf, Rangchary Mukundan, David Cullen, Deborah Myers, Kenneth Neyerlin

Research output: Contribution to journalArticlepeer-review

6 Scopus Citations

Abstract

The degradation of polymer electrolyte membrane fuel cells (PEMFCs) catalyst layers used for heavy-duty vehicles was examined using a catalyst-specific accelerated stress test (AST). High surface area carbon supported dispersed Pt (Pt/ HSC), annealed Pt (a-Pt/ HSC) and PtCo (PtCo/ HSC) alloy catalysts were examined over the course of 90,000 cycles by measuring changes in mass activity, O2 transport resistance, electrochemical active surface area ( ECSA), catalyst accessibility and ionomer-electrocatalyst interactions. Compared to a-Pt/HSC and Pt/HSC catalyst, the PtCo/HSC showed better initial mass activity, a larger initial mass transport loss, and faster degradation after the first 30k AST cycles, as a large portion of Co leached out during potential cycling. Pt/HSC showed higher initial performance relative to a-Pt/HSC but had faster degradation. STEM characterizations show that the ECSA losses are largely related to Pt dissolution resulting in either catalyst particle growth via the Ostwald ripening mechanism or redeposition in the membrane. Catalyst accessibility measurements showed decreased RH sensitivity for all three samples, while CO impedance measurements revealed a decrease in both Pt-water and carbon-water interactions. This implies that, Pt is either preferentially redepositing on the exterior of the carbon support, or that the ionomer is undergoing morphological changes enabling the enhanced intrusion of mesopores.

Original languageAmerican English
Article number232490
Number of pages9
JournalJournal of Power Sources
Volume556
DOIs
StatePublished - 1 Feb 2023

Bibliographical note

Publisher Copyright:
© 2022 Elsevier B.V.

NREL Publication Number

  • NREL/JA-5900-84944

Keywords

  • accelerated stress test
  • catalyst layers
  • heavy-duty vehicles
  • polymer electrolyte membrane fuel cells

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