Precursor-Mediated Dissociation of n-Butane On a Pdo (101) Thin Film

Monday, November 8, 2010: 9:45 AM
Topaz Room (Hilton)
Jose A. Hinojosa, Jason F. Weaver, Can Hakanoglu, Abbin Antony, Jeffery M. Hawkins and Aravind R. Asthagiri, Chemical Engineering, University of Florida, Gainesville, FL

In this study we investigated the molecular adsorption and dissociation of n-butane on a PdO(101) thin film using temperature-programmed reaction spectroscopy (TPRS) experiments and density functional theory (DFT) calculations. We observe that n-butane adsorbs on PdO(101) in a molecular state that is more strongly-bound than n-butane physisorbed on Pd(111). We show that this molecularly adsorbed state of n-butane corresponds to to a σ-complex that forms on the rows of coordinatively unsaturated (cus) Pd atoms of the oxide surface. During TPRS, the n-butane layer undergoes facile C-H bond cleavage below about 215 K and the resulting fragments are completely oxidized by the surface upon continued heating. The evolution of product yields with increasing n-butane coverage as well as site blocking experiments provide strong evidence that the n-butane σ-complex serves as the precursor to initial C-H bond cleavage. Our DFT results further demonstrate that dative bonding between alkane molecules and cus-Pd atoms serves to activate C-H bonds on PdO(101), and suggest that adsorbed σ-complexes play a general role as precursors in alkane activation on transition metal oxide surfaces.

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