Ab initio modelling and investigation of the effects of magnesium oxide surface modifications on single atom catalysis systems

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AydogaKallem_Tez_280223.pdf

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2023-1-23

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Kallem, Aydoğa

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An emerging technology, namely Single Atom Catalysts (SACs) have the potential to bridge the positive characteristics of both heterogenous and homogenous catalysts. In order to create more efficient SACs, it is necessary to understand the metal support interaction (MSI) at the molecular level, which seriously affects the performance of SACs. In this study, the effects of surface modifications on the catalytic performance of SACs were examined via Density Functional Theory (DFT) to gain a deeper understanding of the underlying mechanisms from first principles. Firstly, MgO(100) and MgO(110) surfaces were doped with the Li, Ca, C, Al, Cr, Ni, and N impurity atoms, and the effects of the doped local environment on the Ir SACs were investigated. In the second part of the study, MgO(100) monolayer was modeled as a single-layer film on the Ag(100) and TiN(100) substrates, and the effects of the support systems on the performance of Ir and Rh SACs were analyzed. As a measure of the performance adsorption characteristics of the probe molecule CO was chosen. Adsorption energy, electronic density of states, charge density, and bond order analysis tools were used to characterize CO adsorption. Our results show that adsorption energy/geometry, charge density and bond order values of the Ir/Rh SACs can be affected by both impurity atoms and by the surface atoms which are modified by the impurity atoms or ultrathin film supports. Modified surfaces affected the SACs performances at different levels, these differences were reflected in the adsorption energy/geometry and bond length values of the CO molecule. Hybrid electronic states formed by the Ir/Rh, heteroatoms, and surface oxygen atoms near the Fermi energy level were observed to both alter the occupied and unoccupied electronic states of the CO molecule. The study provides a comprehensive investigation in terms of catalytic performance tuning of SACs by examining the differences and common aspects of various SACs systems.

Subject Keywords

Single atom catalysts, Surface modifications, Impurity atoms, Ultrathin film, Ir metal atom, Rh metal atom, Metal support interaction

URI

https://hdl.handle.net/11511/102554

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

A. Kallem, “Ab initio modelling and investigation of the effects of magnesium oxide surface modifications on single atom catalysis systems,” M.S. - Master of Science, Middle East Technical University, 2023.