Gold Needles in a Haystack

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Science  10 Jul 2009:
Vol. 325, Issue 5937, pp. 127
DOI: 10.1126/science.325_127c
CREDIT: GONZÁLEZ ET AL., ANGEW. CHEM. INT. ED. 48, 10.1002/ANIE.200901308 (2009)

Noble metals such as platinum and gold dispersed on oxide supports are widely used as catalysts, and structural characterization of their morphology is crucial to obtaining mechanistic insight. Electron tomography through adapted scanning transmission electron microscopy has yielded three-dimensional images, but the technique relies on contrasting heavy and light elements (so-called Z-contrast, where Z is the atomic number), and so has largely been applied to systems with light supports. González et al. now extend this method to a system with a much smaller atomic number difference, specifically gold particles supported on a ceria-based mixed oxide, a catalyst that may find application in the production of hydrogen for fuel cells. After either oxidative or reductive treatment of the asprepared catalyst, electron tomography revealed the presence of gold particles that were 1 to 3 nm in diameter. The data showed that the support (blue) consisted mainly of octahedral crystallites joined together through numerous nanocrystal boundaries. The particles (yellow) were concentrated at oxide nanocrystal boundaries or stepped sites of the support.

Angew. Chem. Int. Ed. 48, 10.1002/anie.200901308 (2009).

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