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Hydrogen absorption in 1 nm Pd clusters confined in MIL-101(Cr)

Abstract

We report here the unprecedented modification of the hydrogen absorption/desorption properties of Pd clusters with 1 nm average size relative to bulk and nanoparticles down to 2-3 nm. These metal clusters have been synthesized by a facile double solvent impregnation method. They contain on average 33 atoms and are confined/stabilized into a Metal-Organic-Framework with different metal loadings (5-20 wt%). Such ultra-small nanoparticles are crystalline with the archetypical fcc structure of bulk metal, as confirmed by both HR-TEM and in situ EXAFS. This is the first time, to the best of our knowledge, that 1 nm Pd clusters are effectively confined into a MOF for high metal loadings. Hydrogen absorption/desorption properties of 1 nm Pd clusters have been characterized by both laboratory and synchrotron facilities. At ambient conditions, 1 nm Pd clusters absorb hydrogen forming solid solutions instead of hydride phase, as usually encountered for bulk and Pd nanoparticles down to 2-3 nm. This can be understood by a decrease of the critical temperature of the two-phase region in the Pd-H phase diagram below room temperature. Moreover, the activation energy of hydrogen desorption from Pd clusters strongly decreases relative to bulk Pd. This suggests a change in the rate limiting step from surface recombination or β → α phase transformation usually encountered in bulk Pd to hydrogen diffusion into α and β phases in 1 nm clusters.

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Publication details

The article was received on 14 Aug 2017, accepted on 09 Oct 2017 and first published on 10 Oct 2017


Article type: Paper
DOI: 10.1039/C7TA07159K
Citation: J. Mater. Chem. A, 2017, Accepted Manuscript
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    Hydrogen absorption in 1 nm Pd clusters confined in MIL-101(Cr)

    A. Malouche, G. Blanita, D. Lupu, J. Bourgon, J. Nelayah and C. Zlotea, J. Mater. Chem. A, 2017, Accepted Manuscript , DOI: 10.1039/C7TA07159K

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