Global optimization of PtN clusters supported on CeO2(111)

Plática dada por Lauro Oliver Paz Borbon (IF – UNAM) en el Seminario del Departamento de de la de Ciencias de la UNAM el martes 31 de octubre de 2017 en el Centro de Enseñaza de la Física, CEF, en la Facultad de Ciencias de la UNAM.

One of the most technologically relevant application of oxide supported transition metals lies in heterogeneous catalysis. This is particularly true in emission control systems – such as the catalytic converter of automobiles – where they are usually highly dispersed and known to be oxidized under ambient conditions. One component in the automobile three-way catalytic converter is Pt/CeO2; where Pt serves to oxidize hydrocarbons and carbon monoxide, while ceria (CeO2) acts as an oxygen storage component. Although control at the nm-scale is desirable to open new technological possibilities, there is limited knowledge, both experimentally and theoretically, regarding the geometrical structure and stability of sub-nanometer platinum PtN/CeO2(111) supported clusters.

In this talk, I will describe the implementation of an unbiased Density Functional Theory based global optimization Basin Hopping Monte Carlo algorithm (BH-DFT) to study growth trends of CeO2(111) supported PtN clusters up to 10 atoms in size. From our results, we observe a clear preference for planar 2D structures up to Pt8, followed by a structural transition to 3D structures at Pt9. This remarkable trend is explained by a subtle competition between the formation of strong Pt-O bonds and the cluster internal Pt-Pt bonds. Our calculations show the reducibility of CeO2(111) provides a mechanism to anchor PtN clusters where they become oxidized in a two-way charge transfer mechanism: (a) an oxidation process, where Osurface atoms withdraw charge from Pt atoms forming Pt-O bonds, (b) surface Ce4+ atoms are reduced to Ce3+. In this way, active role of CeO2(111) support in modifying the structural properties and eventual chemical reactivity of sub-nanometer PtN clusters is computationally demonstrated. Finally, global optimization strategies in order to deal with bimetallic platinum-copper (Pt-Cu) supported clusters, within our BH-DFT implementation will be also discussed

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Agradecemos el apoyo de

Erick Tovar quien grabó la plática


Departamento de Matemáticas del CINVESTAV

Facultad de Ciencias de la UNAM