Elucidating the relationships between surface structure and reactivity is important for the rational design of catalysts. This is especially important for metal oxides, where the coordination of exposed metal cations and defect concentrations (e.g. oxygen vacancies) can vary significantly between exposed crystal planes. Surface science studies employing well-defined single crystal metal oxide surfaces have in many cases been instrumental in providing detailed insight into these structure-activity relationships, however these materials are not available for many surfaces of interest. Well-defined nanocrystals of metal oxides provide an intermediary between single crystals and high surface area polycrystalline materials. In this talk, I will present our research using a system of well-defined shape- and size-selected A-TiO<sub>2</sub> nanocrystals (see Figure 1) to study how nanostructure impacts the thermal and photocatalytic reaction pathways of acetaldehyde. The nanocrystals used in this study were either of a platelet morphology, exposing a high fraction of (001) facets, or a truncated bipyramidal morphology, exposing primarily (101) facets, and ranged in size from 10 nm up to 25 nm, and were cast into thin films to employ traditional surface science techniques. Temperature-programmed desorption of acetaldehyde in an ultra-high vacuum environment found that the reactivity of the nanocrystals was strongly dependent on crystallite shape and size. Additionally, it was also found that photoactivity was highly dependent on the morphology of the nanocrystals. These results clearly demonstrate how crystallite size and shape can influence the thermal and photocatalytic properties of a material and gives new insight into how thermal and photocatalytic activity of a material may be tuned by controlling nanostructure.

Insights for catalyst design: Using well-defined metal oxide nanocrystals to elucidate structure-activity relationships

256th National Meeting (2018)

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