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Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 111: Oxides and Insulators: Adsorption II

O 111.1: Talk

Friday, March 16, 2018, 10:30–10:45, MA 041

New Insights into the Catalytic Activity of Solid Solutions: Carbon Dioxide Activation on NiMgO — •Aliaksei Mazheika, Marie-Mathilde Millet, Sabine Wrabetz, Elias Frei, Robert Schlögl, and Sergey V. Levchenko — Fritz-Haber-Institut der MPG, Berlin 14195, Germany

NixMgyO solid solutions are stable and active catalysts for dry reforming of CH4 and CO2 hydrogenation. Despite numerous experimental investigations, the structure of NiMgO surfaces at realistic conditions was unclear. We present a combined hybrid DFT/experimental study of CO2 adsorption at NiMgO surfaces. The DFT calculations are performed with the HSE(α) functional, where the fraction of exact exchange α is set to 0.3 based on a comparison of the HSE(α) and CCSD(T) embedded-cluster calculations. The periodic calculations reveal that NiMg defects prefer to occupy low-coordinated sites (corners and steps) at the MgO (100) surface [1]. Thus, Ni doping promotes formation of such sites during synthesis of the solid solution. Indeed, IR experiments showed that the number of undercoordinated O sites at NiMgO surfaces is significantly increased compared to pristine MgO samples. The stabilization of (110) and reconstructed octopolar (111) surfaces by Ni doping reconciles theoretical results with microcalorimetry measuremenbts of CO2 adsorption energies. The presence of Ni at steps and corners considerably decreases CO2 adsorption energies compared to pure MgO which prevents the carbonation and allows further chemical transformations of CO2.

[1] A. Mazheika and S.V. Levchenko, JPCC 120, 26934 (2016)

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