Evolution of the nanostructure of Pt and Pt–Co polymer electrolyte membrane fuel cell electrocatalysts at successive degradation stages probed by X-ray photoemission

Ali Mushtaq; Agnieszka Witkowska; Mamatimin Abbas; Roberto Gunnella; Andrea Di Cicco

doi:10.1016/j.jpowsour.2014.08.028

Evolution of the nanostructure of Pt and Pt–Co polymer electrolyte membrane fuel cell electrocatalysts at successive degradation stages probed by X-ray photoemission

Abstract

We present a set of XPS (X-ray photoemission spectroscopy) measurements and detailed data-analysis of electrodes for polymer electrolyte membrane fuel cell (PEMFC) based on carbon supported catalysts (Pt and Pt–Co) subjected to a step-like potential cycling (accelerated degradation test). The results of the measurements complete and corroborate parallel TEM (transmission electron microscopy), XRD (X-ray diffraction) and XAS (X-ray absorption spectroscopy) results pointing at a modification of the nanostructure of the catalyst grains. The surface sensitivity of the XPS measurements is used to study the modification of the reactive surface structure of the nanoparticles and the interplay of reactivity and dissolution/precipitation/agglomeration of metal clusters during the catalyst work. The combination of XPS results with XRD, XAS and TEM ones allowed us to obtain a model for the structural changes in Pt–Co nanoparticles occurring during operation. The main structural modifications, in which predominantly Co atoms are involved, occur during the first hours of catalyst operation changing the stoichiometry and degree of disorder in external particles shell. In the last stages of the degradation process, core–shell particles structure, with ordered Pt4Co core and Pt-rich shell (and finally Pt-skin), is formed possibly explaining higher Pt–Co catalyst stability (structural and electrochemical) than pure Pt catalyst.

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Authors (5)

Ali Mushtaq
- . .
Agnieszka Witkowska dr hab. inż.
Mamatimin Abbas
- CNRS, ENSCBP, France Laboratoire IMS
Roberto Gunnella
- . .
Andrea Di Cicco
- University of Camerino, Italy Physics Division, School of Science and Technology

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Category:: Articles
Type:: artykuł w czasopiśmie wyróżnionym w JCR
Published in:: JOURNAL OF POWER SOURCES no. 271, pages 548 - 555,
ISSN: 0378-7753
Language:: English
Publication year:: 2014
Bibliographic description:: Mushtaq A., Witkowska A., Abbas M., Gunnella R., Di Cicco A.: Evolution of the nanostructure of Pt and Pt–Co polymer electrolyte membrane fuel cell electrocatalysts at successive degradation stages probed by X-ray photoemission// JOURNAL OF POWER SOURCES. -Vol. 271, (2014), s.548-555
DOI:: Digital Object Identifier (open in new tab) 10.1016/j.jpowsour.2014.08.028
Verified by:: Gdańsk University of Technology