Preparation and Structural Analysis of Carbon-Supported Co Core/Pt Shell Electrocatalysts Using Electroless Deposition Methods

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• 作者：K. D. Beard ; David Borrelli ; Alison M. Cramer ; D. Blom ; J. W. Van Zee ; John R. Monnier
• 刊名：ACS Nano
• 出版年：2009
• 出版时间：September 22, 2009
• 年：2009
• 卷：3
• 期：9
• 页码：2841-2853
• 全文大小：807K
• 年卷期：0
• ISSN：1936-086X

文摘

Cobalt core/platinum shell nanoparticles 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 mass basis, only the lower Pt:Co atomic ratio Pt−Co/C catalysts outperformed the Pt/C catalyst.