Regensburg 2016 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 31: Heterogeneous Catalysis: Theory
O 31.5: Vortrag
Dienstag, 8. März 2016, 11:30–11:45, S053
Hydrogen coadsorption effects on C-C bond formation on Ru(0001) at realistic temperatures and pressures: An ab initio study — •Xunhua Zhao, Sergey V. Levchenko, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin
Hydrogen coadsorption is a crucial component of heterogeneous catalysis of hydrocarbons. Our recent study [1] demonstrated the critical role of hydrogen coadsorption in the stabilization of CH2 species on the Ru(0001) surface. In the present work, we report a DFT-PBE study of hydrogen coadsorption effects on C-C bond formation reactions at realistic conditions up to typical temperature and hydrogen pressure of Fischer-Tropsch synthesis (FTS) [2]. Ab initio atomistic thermodynamics is employed to assess the relative thermo-stability of CHx species, and the string method is used to evaluate the minimum-energy paths for C-C bond formation. CHx+CHy and CHx+C2Hz (x,y=1,2,3 and z=3−6) coupling reactions at the monolayer coverage for coadsorbed hydrogen plus reactants are studied to identify possible chain-growth paths in FTS. For comparison, coupling reactions without hydrogen coadsorption are also calculated. It is found that in general hydrogen coadsorption shifts the relative stability to more hydrogen-saturated species (larger x in CHx for instance). Hydrogen coadsorption is found to have a profound influence on the C-C coupling reaction barriers: While it generally reduces all the barriers, some reaction paths become more favoured in the presence of the coadsorbed hydrogen. — [1] H. Kirsch, X. Zhao et. al., J. Catal. 320, 89 (2014); [2] R. A. Van Santen et. al., Adv. Catal. 54, 127 (2011)