Regulating Photochemical Selectivity with Temperature: Isobutanol on TiO2(110)

Carla Courtois, Constantin A. Walenta, Martin Tschurl, Ueli Heiz, Cynthia M. Friend

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Selective photocatalytic transformations of chemicals derived from biomass, such as isobutanol, have been long envisioned for a sustainable chemical production. A strong temperature dependence in the reaction selectivity is found for isobutanol photo-oxidation on rutile TiO2(110). The strong temperature dependence is attributed to competition between thermal desorption of the primary photoproduct and secondary photochemical steps. The aldehyde, isobutanal, is the primary photoproduct of isobutanol. At room temperature, isobutanal is obtained selectively from photo-oxidation because of rapid thermal desorption. In contrast, secondary photo-oxidation of isobutanal to propane dominates at lower temperature (240 K) due to the persistence of isobutanal on the surface after it is formed. The byproduct of isobutanal photo-oxidation is CO, which is evolved at higher temperature as a consequence of thermal decomposition of an intermediate, such as formate. The photo-oxidation to isobutanal proceeds after thermally induced isobutoxy formation. These results have strong implications for controlling the selectivity of photochemical processes more generally, in that, selectivity is governed by competition of desorption vs secondary photoreaction of products. This competition can be exploited to design photocatalytic processes to favor specific chemical transformations of organic molecules.

Original languageEnglish
Pages (from-to)13072-13080
Number of pages9
JournalJournal of the American Chemical Society
Volume142
Issue number30
DOIs
StatePublished - 29 Jul 2020
Externally publishedYes

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