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Shape-dependence of the thermal and photochemical reactions of methanol on nanocrystalline anatase TiO2.

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Title: Shape-dependence of the thermal and photochemical reactions of methanol on nanocrystalline anatase TiO2.
Authors: Bennett, David A.1, Cargnello, Matteo2, Diroll, Benjamin T.3, Murray, Christopher B.3, Vohs, John M.1 vohs@seas.upenn.edu
Source: Surface Science. Dec2016, Vol. 654, p1-7. 7p.
Subjects: Titanium dioxide, Photooxidation, Methanol, Chemical reactions, Nanoparticles analysis, Particle size distribution, Structure-activity relationships
Abstract: Structure-activity relationships and the influence of particle size and shape on the partial- and photo-oxidation of methanol on nanocrystalline anatase TiO 2 were investigated using temperature-programmed desorption. The study employed two distinct nanoparticle morphologies: truncated bipyramids exposing primarily {101} facets, and flatter platelets exposing primarily {001} surfaces, whose nominal sizes ranged from 10 to 25 nm. The platelets were found to be more active for thermally-driven reactions, such as coupling of methoxide groups to produce dimethyl ether, and deoxygenation to produce methane. A dependence of the reactivity of {001} facets for the coupling of methoxide groups to produce dimethyl ether on facet size was also observed. In contrast to the thermally-driven reactions, the bipyramidal nanoparticles were observed to be more active for a range of photochemical reactions, including oxidation and coupling to produce methyl formate, and photo-decomposition of surface methoxide species. This study also shows how well-defined nanocrystals can be used to help bridge the materials gap between studies of single crystal model catalysts and their high surface area industrial analogs. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Structure-activity relationships and the influence of particle size and shape on the partial- and photo-oxidation of methanol on nanocrystalline anatase TiO 2 were investigated using temperature-programmed desorption. The study employed two distinct nanoparticle morphologies: truncated bipyramids exposing primarily {101} facets, and flatter platelets exposing primarily {001} surfaces, whose nominal sizes ranged from 10 to 25 nm. The platelets were found to be more active for thermally-driven reactions, such as coupling of methoxide groups to produce dimethyl ether, and deoxygenation to produce methane. A dependence of the reactivity of {001} facets for the coupling of methoxide groups to produce dimethyl ether on facet size was also observed. In contrast to the thermally-driven reactions, the bipyramidal nanoparticles were observed to be more active for a range of photochemical reactions, including oxidation and coupling to produce methyl formate, and photo-decomposition of surface methoxide species. This study also shows how well-defined nanocrystals can be used to help bridge the materials gap between studies of single crystal model catalysts and their high surface area industrial analogs. [ABSTRACT FROM AUTHOR]
ISSN:00396028
DOI:10.1016/j.susc.2016.07.009