Size-Dependent Self-Limiting Oxidation of Free Palladium Clusters

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• 作者：Sandra M. Lang ; Irene Fleischer ; Thorsten M. Bernhardt ; Robert N. Barnett ; Uzi Landman
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：September 18, 2014
• 年：2014
• 卷：118
• 期：37
• 页码：8572-8582
• 全文大小：568K
• ISSN：1520-5215

文摘

Temperature-dependent gas phase ion trap experiments performed under multicollision conditions reveal a strongly size-dependent reactivity of Pd_x⁺ (x = 2鈥?) in the reaction with molecular oxygen. Yet, a particular stability and resistance to further oxidation is generally observed for reaction products with two oxygen molecules, Pd_xO₄⁺. Complementary first-principles density functional theory simulations elucidate the details of the size-dependent bonding of oxygen to the small palladium clusters and are able to assign the pronounced occurrence of Pd_xO₄⁺ complexes to a dissociatively chemisorbed bridging oxygen atomic structure which impedes the chemisorption of further oxygen molecules. The molecular physisorption of additional O₂ is only observed at cryogenic temperatures. Additional experiments and simulations employing preoxidized clusters Pd_xO⁺ (x = 2鈥?) and Pd_xO₂⁺ (x = 4鈥?) confirm the formation of the two different oxygen species.