Strained lattice with persistent atomic order in Pt3Fe 2 intermetallic core-shell nanocatalysts

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Journal titleACS Nano
Pages61036110; # of pages: 8
SubjectAberration-corrected scanning transmission electron microscopies; Compositional analysis; Enhanced catalytic activity; Lattice strain; Nanocatalysts; Oxygen reduction reaction; Scanning transmission electron microscopy; Two Dimensional (2 D); Atoms; Catalyst activity; Degradation; Durability; Electrolytic reduction; Energy dispersive spectroscopy; Proton exchange membrane fuel cells (PEMFC); Shells (structures); Surface relaxation; Transmission electron microscopy; Two dimensional; X ray diffraction; Platinum
AbstractFine-tuning nanocatalysts to enhance their catalytic activity and durability is crucial to commercialize proton exchange membrane fuel cells. The structural ordering and time evolution of ordered Pt3Fe2 intermetallic core-shell nanocatalysts for the oxygen reduction reaction that exhibit increased mass activity (228%) and an enhanced catalytic activity (155%) compared to Pt/C has been quantified using aberration-corrected scanning transmission electron microscopy. These catalysts were found to exhibit a static core-dynamic shell regime wherein, despite treating over 10 000 cycles, there is negligible decrease (9%) in catalytic activity and the ordered Pt 3Fe2 core remained virtually intact while the Pt shell suffered a continuous enrichment. The existence of this regime was further confirmed by X-ray diffraction and the compositional analyses using energy-dispersive spectroscopy. With atomic-scale two-dimensional (2-D) surface relaxation mapping, we demonstrate that the Pt atoms on the surface are slightly relaxed with respect to bulk. The cycled nanocatalysts were found to exhibit a greater surface relaxation compared to noncycled catalysts. With 2-D lattice strain mapping, we show that the particle was about -3% strained with respect to pure Pt. While the observed enhancement in their activity is ascribed to such a strained lattice, our findings on the degradation kinetics establish that their extended catalytic durability is attributable to a sustained atomic order.
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AffiliationEnergy, Mining and Environment; National Research Council Canada
Peer reviewedYes
NPARC number21270349
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Record identifier747146e2-9b5a-4b16-91f0-23ba20313fb7
Record created2014-02-04
Record modified2016-05-09
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