(98d) Density Functional Theory Studies of C-H Activation On a Pdo(101) Thin Film Grown On Pd(111)

Understanding alkane activation on transition metal oxide surfaces is important since several applications of oxidation catalysis occur under conditions that cause TM surfaces to oxidize, often resulting in dramatic changes in catalytic properties. We have performed density functional theory (DFT) calculations on the adsorption and reactivity of alkanes on the PdO(101) surface that forms on Pd(111) under oxygen-rich conditions. The coordinatively unsaturated (cus) Pd atoms on the PdO(101) surface form sigma-complexes with alkanes. The dative bonding between cus-Pd and the alkanes weaken C-H bonds, which is reflected by bond elongation and significant vibrational-mode softening. For methane, we predict that coordination with a cus-Pd atom lowers the barrier for C-H bond cleavage on PdO(101) by more than 100 kJ/mol. These results demonstrate that dative bonding between alkane molecules and cus-Pd atoms serves to electronically activate C-H bonds on PdO(101), and suggest that adsorbed sigma-complexes play a general role as precursors in alkane activation on transition metal oxide surfaces.