Compositional and morphological changes for ordered PtxFey/CO2 electro-reduction catalysts

Alternative titleCompositional and Morphological Changes for Ordered PtxFey/CO2 Electro-Reduction Catalysts
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DOIResolve DOI: http://doi.org/10.1002/cctc.201200614
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TypeArticle
Journal titleChemCatChem
ISSN1867-3880
Volume5
Issue6
Pages14491460; # of pages: 12
SubjectO2 reduction catalysts; Lifetime; PEMFC; HAADF-STEM; EDX spot and line analyses
AbstractChanges in O2 reduction activity (orr) and structural changes of carbon supported catalysts upon electrochemical stress testing are investigated. Focus is placed on two alloy catalysts of nominal Pt3Fe/C and Pt3Fe2/C compositions. Energy dispersive X-ray Spectroscopy (EDXS) spot and line analyses reveal a dependence of the Fe composition on the particle size particularly for he two as-prepared catalysts. Catalyst particles are shown to exist of a Pt enriched shell and a PtxFey alloy core. Larger (larger ca. 10 nm) particles are shown to have a higher Fe content that approaches the nominal composition suggesting that the smaller (smaller than 6 nm) Pt catalyst particles are more difficult to alloy. HAADF-STEM, XRD, and scanning electron microscope (SEM) with EDXS show that Fe is gradually lost from the catalyst particles as a result of extensive potential (E)-cycling. Changes upon E-cycling are most clearly observed for the small (smaller than 3 nm) particles, for which, Fe is almost entirely depleted. However, the catalytic orr activities remain constant over an extensive cycling period for the PtxFey/C catalysts. In fact, the mass orr activities are seen to decrease proportionally with the Pt surface area (Apt). The histograms before and after cycling are compared to observed changes in APt, and are also discussed in comparison to E-holding experiments. It is concluded that the dissolution of Pt is a strong contributor for the observed drop in APt and mass orr activity for the PtxFey/C catalysts. The continuous transition between Pt-oxide formation and its reduction to Pt metal is suggested to play a major role for the degradation of the PtxFey/C catalysts studied in this work.
Publication date
LanguageEnglish
AffiliationEnergy, Mining and Environment; National Research Council Canada
Peer reviewedYes
NRC numberNRC-EME-53170
NPARC number21268530
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Record identifier6ecb0940-ab05-4ad0-92f5-0d90b8587288
Record created2013-09-13
Record modified2016-05-09
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