Journal
ACS NANO
Volume 3, Issue 9, Pages 2841-2853Publisher
AMER CHEMICAL SOC
DOI: 10.1021/nn900214g
Keywords
electroless deposition; platinum; cobalt; core/shell; bimetallic catalyst; oxygen reduction reaction
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Funding
- NSF [EEC-0324260]
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Cobalt core/platinum shell nanciparticles were prepared by the electroless deposition (ED) of Pt on carbon-supported cobalt catalyst (Co/C) and verified by HRTEM images. For a 2.0 wt % Co/C core, the ED technique permitted the Pt loading to be adjusted to obtain a series of bimetallic compositions with varying numbers of monolayers (ML). The tendency for corrosion of Co and the electrochemical (i.e., oxygen reduction reaction (ORR)) activity of the structures were measured. The results from temperature-programmed reduction (TPR) analysis suggest that a single Pt ML coverage is formed at a Pt weight loading between 0.5 and 0.7% on the 2.0% Co/C. HRTEM analysis indicates that the continuity of the Pt shell on the Co core depends on the precursor Co particle size, where large Co particles (> 10 nm) favor noncontinuous, three-dimensional Pt structures and small Co particles (<6 nm) favor layer-by-layer growth. For these larger core-shell particles, Co was observed to quickly corrode in 0.3 M H2SO4. Surface area specific ORR activity, measured by chemisorption techniques, revealed that the Pt-Co/C catalysts performed better than a commercial Pt/C catalyst; however, on a Pt/C mass basis, only the lower Pt:Co atomic ratio Pt-Co/C catalysts outperformed the Pt/C catalyst.
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