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Investigating catalytic activity at oxide surfaces using a QM/MM methodology

A set of complementary studies has been undertaken to investigate the interaction of CO2 with metal oxide surfaces. Beginning with the simple and well-studied magnesium oxide surface, work progressed to include a manganese dopant near the MgO active site before shifting to manganese oxide. All work made use of the Quantum Mechanical/Molecular Mechanical (QM/MM) methodology implemented within the ChemShell code, which combines information from an electronic structure calculation on atoms in the vicinity of the adsorption site with relaxation effects from a large component of the surrounding catalyst system. Initial findings showed that CO2 interacts favourably with the MgO (100) terrace, and that the presence of trapped electrons at surface oxygen vacancies opens up the possibility for catalytic chemical processes to occur. Particular attention was paid to the CO2 radical anion species formed when the adsorbate binds to a vacancy containing a single electron, and the addition of hydrogen to the surface-adsorbate complex allowed for a number of catalytic cycles to be identi- fied. Manganese doping was used to investigate the effect of a transition metal on the interaction between the adsorbate and the vacancy, before moving on to the transition metal oxide where more complex effects such as lattice distortion and antiferromagnetic ordering were included in the model. Finally, work was performed on the related system Li-doped MgO in order to investigate an open question regarding the activation barrier for methyl radical formation as part of the oxidative coupling of methane reaction.
Date January 2015
CreatorsDowning, C. A.
PublisherUniversity College London (University of London)
Source SetsEthos UK
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation

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