PhD Thesis Defenses

PhD Thesis defense: Le Fantôme de l’Opéra - Studies on Atoms and Electrons Beneath

The carbon dioxide reduction reaction is a hopeful candidate to ecological challenges of our age, due to its capability of reducing carbon dioxide emission generated from the combustion of fossil fuels and converting carbon dioxide into valuable hydrocarbons. Oxide-derived metal nanostructures have been synthesized, many of which exhibit unique catalytic characteristics for facilitating carbon dioxide reduction reactions. The stability, influence and effects of subsurface oxygen atoms are investigated with theoretical computations with various levels of theory and models. It is found that the presence of subsurface oxygen atoms, which are stable, enhances the CO adsorption and hence its coverage on oxide-derived Cu surface, due to the reduced σ-repulsion, breaking the scaling relations. Albeit it does not directly reduce the CO dimerization barrier, the adsorption of H atoms is inhibited thus steering the selectivity. The presence of subsurface oxygen atoms is concluded from a joint work with experimental and theoretical efforts of X-ray photoelectron spectroscopy. The precursor region of CO desorption from Ru(0001) is studied with the transition potential method, whereas for the simulation of the Xray spectroscopies on p4g C/Ni(100) which is a surface reconstruction when carbon atoms adsorb on Ni(100), vibrational effects are also needed for understanding the experimental data.

Keywords: Carbon dioxide reduction, Subsurface oxygen, X-ray spectroscopy, Density functional theory, CO