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O: Fachverband Oberflächenphysik

O 8: Oxides and insulators: Adsorption I

O 8.7: Vortrag

Montag, 14. März 2011, 12:45–13:00, WIL C307

DFT studies of reaction mechanisms of methane combustion on PdO(100) — •Arezoo Dianat¹, Manfred Bobeth², and Lucio Colombi Ciacchi¹ — ¹Faculty of Production Engineering, University of Bremen, 28359 Bremen, Germany — ²Institute for Materials Science, Dresden University of Technology, 01062 Dresden, Germany

Palladium oxides are renowned for their high activity in the catalytic combustion of methane. We have investigated the complex reaction mechanisms of methane combustion on the PdO(100) surface within the framework of density functional theory. From an analysis of the calculated driving forces and activation energies for the dissociative adsorption of methane and the successive dehydrogenation of adsorbed hydrocarbons, we conclude that the experimentally observed conversion rates at temperatures of about 600 K cannot be explained in terms of direct dehydrogenation processes.

Investigations of alternative reaction routes reveal that the reaction of oxygen molecules from the gas phase with hydrogen previously adsorbed on the catalyst surface can efficiently produce water. According to combined ab initio molecular dynamics and static total energy calculations, the combustion reaction proceeds through the spontaneous formation of H2O2 followed by its dissociation and water formation with an activation energy of about 0.7 eV. Following an analogous mechanism, oxygen molecules from the gas phase can also react with adsorbed CH3 groups to produce CH2O as an intermediate reaction product.