Monitoring the Morphological Changes of Skeleton-PtCo Electrocatalyst during PEMFC Start-Up/Shut-Downprobed by in situ WAXS and SAXS

authored by
Marek Janssen, Jakub Drnec, Isaac Martens, Jonathan Quinson, Rebecca Pittkowski, Daesung Park, Philipp Weber, Matthias Arenz, Mehtap Oezaslan
Abstract

Advanced in situ analyses are indispensable for comprehending the catalyst aging mechanisms of Pt-based PEM fuel cell cathode materials, particularly during accelerated stress tests (ASTs). In this study, a combination of in situ small-angle and wide-angle X-ray scattering (SAXS & WAXS) techniques were employed to establish correlations between structural parameters (crystal phase, quantity, and size) of a highly active skeleton-PtCo (sk-PtCo) catalyst and their degradation cycles within the potential range of the start-up/shut-down (SUSD) conditions. Despite the complex case of the sk-PtCo catalyst comprising two distinct fcc alloy phases, our complementary techniques enabled in situ monitoring of structural changes in each crystal phase in detail. Remarkably, the in situ WAXS measurements uncover two primary catalyst aging processes, namely the cobalt depletion (regime I) followed by the crystallite growth via Ostwald ripening and/or particle coalescence (regime II). Additionally, in situ SAXS data reveal a continuous size growth over the AST. The Pt-enriched shell thickening based on the Co depletion within the first 100 SUSD cycles and particle growth induced by additional potential cycles were also collaborated by ex situ STEM-EELS. Overall, our work shows a comprehensive aging model for the sk-PtCo catalyst probed by complementary in situ WAXS and SAXS techniques.

Organisation(s)
QuantumFrontiers
External Organisation(s)
Technische Universität Braunschweig
European Synchrotron Radiation Facility
Aarhus University
University of Copenhagen
National Metrology Institute of Germany (PTB)
University of Bern
Type
Article
Journal
CHEMSUSCHEM
ISSN
1864-5631
Publication date
20.03.2024
Publication status
E-pub ahead of print
Peer reviewed
Yes
ASJC Scopus subject areas
Environmental Chemistry, Chemical Engineering(all), Materials Science(all), Energy(all)
Electronic version(s)
https://doi.org/10.1002/cssc.202400303 (Access: Open)