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Golfetto E.,University of Trieste | Golfetto E.,Laboratorio Nanotecnologie per LEnergia | Baraldi A.,Laboratorio Nanotecnologie per LEnergia | Baraldi A.,CNR Institute of Neuroscience | And 14 more authors.
Journal of Physical Chemistry C | Year: 2010

We have addressed the problem of determining a reliable experimental descriptor of surface chemical reactivity by measuring Pd and Ru 3d 5/2 core-level shifts of the Pdn/Ru(0001) pseudomorphic overlayer system (n ) 0-3) by high resolution X-ray photoelectron spectroscopy. We find a linear relationship between the calculated theoretical changes of the d-band center position projected on each Ru and Pd atomic layer (which is, according to the Hammer and Norskov d-band model, a good theoretical descriptor of chemical reactivity) and the corresponding core-level shifts, both for the Ru atomic planes and for the Pd overlayers. Core-level shifts, therefore, should be considered as reliable experimental descriptors of chemical reactivity in the same sense (and with similar limitations) of the theoretical descriptor d-band center. Final-state effect contributions to the shifts do not obscure this trend. © 2010 American Chemical Society.

Chen G.,INRS - Institute National de la Recherche Scientifique | Desinan S.,INRS - Institute National de la Recherche Scientifique | Rosei R.,Laboratorio Nanotecnologie per LEnergia | Rosei R.,McGill University | And 3 more authors.
Chemistry - A European Journal | Year: 2012

We report the synthesis and characterization of new Ni xRu 1üx (x= 0.56-0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet-chemistry method using a rapid lithium triethylborohydride reduction of Ni 2+ and Ru 3+ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We found that the as-prepared Ni-Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni-Ru alloy NPs, and in particular the Ni 0.74Ru 0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru coreshell NPs. The hydrolysis activation energy for the Ni 0.74Ru 0.26 alloy catalyst was measured to be approximately 37 kJmol ü1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJmol ü1) and Ru NPs (≈49 kJmol ü1), and for Ni@Ru (≈44 kJmol ü1), and is also lower than the values of most noblemetal-containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal. © 2012 Wiley-VCH Verlag GmbH& KGaA, Weinheim.

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