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TitleMorphological Dependence of the Thermal and Photochemical Reactions of Acetaldehyde on Anatase TiO2 Nanocrystals
AuthorPaul A. Pepin Benjamin T. Diroll Christopher B. MurrayJohn M. Vohs
Affiliation(s)1.Department of Chemical and Biomolecular EngineeringUniversity of PennsylvaniaPhiladelphiaUSA 2.Department of ChemistryUniversity of PennsylvaniaPhiladelphiaUSA 3.Department of Materials Science and EngineeringUniversity of PennsylvaniaPhiladelphiaUSA 4.Center for Nanoscale MaterialsArgonne National LaboratoryLemontUSA
Published 
KeywordAnatase TiO2 TPD UHV Acetaldehyde Photo-oxidation
SnippetThe chamber was also equipped with a fiber optic feedthrough connected to a 365 nm UV light source (Prizmatix), and a dosing nee- dle
AbstractSize and shape selected anatase TiO2 (A-TiO2) nanocrystals that had either a truncated bipyramidal morphology exposing predominantly (101) facets, or a platelet morphology exposing a high fraction of (001) facets and ranging in size from 10 to 25 nm were used to study the influence of crystallite shape and size on the thermal and photocatalytic reactions of acetaldehyde on TiO2 using temperature-programmed desorption in ultra-high vacuum. The primary thermal reaction pathways on the bipyramidal and platelet nanocrystals were aldol condensation to produce crotonaldehyde and reductive coupling to butene. The platelet morphology, however, exhibited higher thermal activity, which was attributed to the higher fraction of exposed (001) facets. For both morphologies crystallite size was found to be important with smaller nanocrystals favoring butene and larger ones favoring crotonaldehyde. The dependence of the selectivity on crystallite size can be attributed to the populations of planar and edge sites exposed by the nanocrystals. The photocatalytic activity of the nanocrystals was also found to vary with size and shape with the platelets having higher activity for acetaldehyde photo-oxidation than the bipyramidal morphology. For both morphologies, photoactivity also increased as the size of the nanocrystals increased.

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