Abstract:

Oxides are used as catalysts for a large number of oxidation and oxidative dehydrogenation reactions. We use density functional to explore the catalytic properties of two classes of compounds. In one the cation M in the oxide MxOy is replaced with a metal N to form the doped oxide NzMx-zOy. Our intention is to determine to what extent the doped oxide is a better oxidation catalyst than the host oxide. We find that many dopants make the oxygen atoms at the surface of the oxide more ready to engage in oxidation reactions. The oxidation reaction forms an oxygen vacancy on the surface which has to be healed if the system is to be a catalyst. This happens if the system adsorbs oxygen at the vacancy site and activates it so that it will also take part in an oxidation reaction. One oxygen atom is taken away by the oxidation product and the other fills the oxygen vacancy. A good oxidation catalyst will have to reach a good compromise between these steps. We will discuss the activity of a large number of dopants of titania, ceria and zinc oxide. We also examine a system consisting of VOx clusters supported on various oxide surfaces, which can also be viewed as a doped oxide. If there is time we will discuss several issues related to the catalytic activity of very small gold clusters supported on rutile.
 
 
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