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Langmuir. 2010 Feb 16;26(4):2894-903. doi: 10.1021/la902756j.

Pt-encapsulated Pd-Co nanoalloy electrocatalysts for oxygen reduction reaction in fuel cells.

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  • 1Electrochemical Energy Laboratory, Materials Science and Engineering Program, The University of Texas at Austin, Austin, Texas 78712, USA.

Abstract

Pt-encapsulated Pd(x)Co(100-x) nanoalloy electrocatalysts supported on carbon have been synthesized by a rapid microwave-assisted solvothermal (MW-ST) method within 15 min at as low as 300 degrees C. Subsequently, the samples have been heat treated at 900 degrees C in a reducing gas atmosphere to obtain Pt-Pd-Co nanoalloys. X-ray diffraction (XRD) analysis of the as-synthesized and 900 degrees C heat-treated samples reveals interesting changes in phase compositions and degree of alloying with Co and Pt contents and heat treatment. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) data of the as-synthesized samples confirm Pt enrichment on the surface of the Pd-Co nanoparticles. Rotating disk electrode (RDE) and single cell proton exchange membrane fuel cell measurements reveal that the as-synthesized Pt-encapsulated Pd(80)Co(20) (i.e., 75 wt % Pd(80)Co(20) + 25 wt % Pt) with 20 wt % total metal loading on carbon or 5 wt % Pt exhibit higher catalytic activity for the oxygen reduction reaction (ORR) compared to Pt with 20 wt % Pt loading on carbon. Significant changes in the catalytic activity for ORR occur on heat treatment at 900 degrees C as a result of changes in the phase composition and increase in particle size. This study demonstrates that the encapsulation of Pd-Co alloys with Pt offers a significant enhancement in activity for ORR per unit mass of Pt, offering a significant cost savings.

PMID:
20141217
[PubMed]
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