Palladium nanoparticles have received considerable attention due to their potential applications in catalysts, magnetic storage materials, and hydrogen storage materials, esp. in selective hydrogenation of pyrolysis gasoline for potential extracting benzene, toluene and xylene (BTX). This paper systematically presents a series of experiments with 2 nm Pd nanoclusters where we investigated temperature-dependent changes in the Pd-Pd bond length and its mean squared disorder under hydrogen by in situ EXAFS analysis. XAS studies revealed that these materials possess a dramatically nonbulklike nature. Under an ambient atmosphere, the clusters exhibit relaxations of the M-M bond distances, negative thermal expansion (NTE), and large bond length disorder. Whereas under ambient hydrogen atmosphere, bond distance is markedly increased at lower temperature due to hydrogen induced expansion of lattice while the contraction occurs at high temperature by desorption of hydrogen. The temperature-dependent behaviors may illustrate the excellent catalytic properties for Pd catalyst occurs at low temperatures.

Temperature-dependent structure changes of palladium clusters in hydrogen and helium atmospheres

243rd National Meeting (2012)

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