Saving Nickels and Coppers

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Science  16 Apr 2004:
Vol. 304, Issue 5669, pp. 361
DOI: 10.1126/science.304.5669.361b

The expensive metals palladium and platinum are used to catalyze many chemical reactions. Because reactions occur only at the surfaces of catalysts, nanoparticles are of interest because they offer a high surface-to-volume ratio and because it may be possible to use a cheaper metal for the core. For bimetallic particles including copper or nickel, palladium often ends up in the nanoparticle core, probably because Pd ions are more readily reduced.

Son et al. have developed a metal-surfactant decomposition reaction that leads to Pd-coated Ni nanoparticles. When they heated a mixture of metal-trioctylphosphine complexes (Pd-TOP and Ni-TOP), they observed that Ni-TOP decomposed at a lower temperature, resulting in Ni nanoparticles onto which Pd deposited as the temperature was raised. Catalytic activity was assessed for the Sonogashira coupling reaction, which involves the coupling of terminal alkynes with aryl or vinyl halides. At equal amounts of Pd, the Ni/Pd core/shell particles showed greater reactivity than those of pure Pd and could be recycled many times. — MSL

J. Am. Chem. Soc. 10.1021/ja039757r (2004).

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