Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 72: Oxide and Insulator Surfaces: Adsorption I

O 72.7: Vortrag

Mittwoch, 22. März 2017, 12:00–12:15, WIL C107

The effect of Ni substitutional defects on the structure and chemical properties of MgO surfaces — •Aliaksei Mazheika and Sergey V. Levchenko — Fritz-Haber-Institut der MPG

Ni-MgO solid solutions are promising materials for catalytic reduction of CO2 and dry reforming of CH4. To explain the catalytic activity, an ab initio study of Ni-substitutional defects in MgO (NiMg) has been performed. At first, the validation of the theory level was done. We compared results of CCSD(T) embedded-cluster calculations of NiMg formation energies and adsorption energies of CO, CO2 and H2 on them to the HSE(α) hybrid DFT functional with the fraction of the exact exchange α varied between 0 and 1 [1]. HSE(0.3) was found to be the best compromise in this study. Our periodic HSE(0.3) calculations show that NiMg defects are most stable at corner sites, followed by steps, and are least stable at (001) terraces. Thus, Ni-doping stabilizes stepped MgO surfaces. The dissociative adsorption of H2 on the terrace is found to be endothermic (+1.1 eV), whereas on (110) surface with NiMg it is highly exothermic (−1.6 eV). Adsorbed CO2 is also significantly stabilized (−0.6 vs. −2.2 eV). These findings explain recent microcalorimetry measurements of H2 and CO2 adsorption at doped Ni-MgO samples [2].—[1] A. Mazheika and S.V. Levchenko, DOI: 10.1021/acs.jpcc.6b09505; [2] A. Mazheika, M.-M. Millet, S. Wrabetz, A. Tarasov, E. Frei, S.V. Levchenko, A. Trunschke and R. Schlögl, manuscript in preparation.

This work was funded by the UNICAT cluster of excellence.

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