How surface reparation prevents catalytic oxidation of CO on atomic gold at defective MgO(001) surfaces
Jean Christophe Tremblay a, Kai Töpfer a
a Freie Universität Berlin, Arnimallee 14, Berlin, Germany
Materials for Sustainable Development Conference (MATSUS)
Proceedings of September Meeting 2016 (NFM16)
Berlin, Germany, 2016 September 5th - 13th
Organizers: Marin Alexe, Enrique Cánovas, Celso de Mello Donega, Ivan Infante, Thomas Kirchartz, Maksym Kovalenko, Federico Rosei, Lukas Schmidt-Mende, Laurens Siebbeles, Peter Strasser, Teodor K Todorov, Roel van de Krol and Ulrike Woggon
Poster, Kai Töpfer, 443
Publication date: 14th June 2016

We study from first principles the co-adsorption and catalytic behaviors of CO and O2 on a single gold atom deposited at defective magnesium oxide surfaces. Using cluster models and point charge embedding within a density functional theory framework, we simulate the CO oxidation reaction for Au1 on differently charged oxygen vacancies of MgO(001) to rationalize its experimentally observed lack of catalytic activity. Our results show that: 1) co-adsorption is weakly supported at F0 and F2+ defects but not at F1+ sites, 2) electron redistribution from the F0 vacancy via the Au1 cluster to the adsorbed molecular oxygen weakens the O2 bond, as required for a sustainable catalytic cycle, 3) a metastable carbonate intermediate can form on defects of F0 type, 4) there exists only a small activation barrier for the highly favorable dissociation of CO2 from F0 , and 5) the moderate adsorption energy of the gold atom on the F0 defect cannot prevent insertion of molecular oxygen inside the defect. Due to the lack of protection of the color centers, the surface becomes invariably repaired by the surrounding oxygen and the catalytic cycle is irreversibly broken at the first oxidation step.



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