Structure Sensitivity and Selectivity of Reactions on Metal Oxide Surfaces

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This is a study of the structural requirements and selectivity of reactions on oxide surfaces with the objective of determining those factors important for the design of new catalytic oxide materials. Adsorption and reaction on single crystals of zinc oxide and titania are studied to determine the structure sensitivity of archetypal reactions. Processes studied include proton transfer and nucleophilic oxidation on the zinc polar face of zinc oxide, electrophilic substitution on the oxygen polar face, and activation of difunctional species on the prism faces. Relative surface-adsorbate bond strengths on polycrystalline oxide powders are determined quantitatively in order to elucidate the nature of the surface-adsorbate bond and its dependence on both moieties; this may explain the surprising selectivities observed for hydrocarbon and oxygenate reactions on zinc oxide. Ultimately, this work should lead to principles for design and synthesis of novel oxide materials for use as catalysts and sensors.