Photoreactions of Organic Compounds with TiO2 Single Crystal Surfaces

Abstract

In this work the photoreactions of two organic molecules: acetic acid and ethanol, over rutile TiO 2 (110), TiO 2 (011) and the (011) reconstructed surface of TiO 2 (001) single crystals are presented. Comparison with the corresponding dark reaction is also given. The steady state reaction at 320 K of acetic acid over the {011}-faceted surface of TiO 2 (001) under UV irradiation indicated the formation of methane, ethane and CO 2 . These are the expected products of the socalled "Photo-Kolbe" reaction of acetic acid. While the formation of methane was not sensitive to the addition of molecular oxygen and could be carried out in UHV conditions catalytically that of ethane required the continual addition of gas phase molecular oxygen for its photo-catalytic production to occur. The quantum yield of the reaction was computed equal to 0.05, while the depletion layer width and barrier height were found equal to 18 nm and 0.18 eV, respectively. The photoreaction of ethanol conducted over the rutile TiO 2 (110) surface indicated that, oxidation of ethoxides to acetate species occurs under molecular oxygen within the investigated pressure range (10 À6 -10 À9 torr). In the absence of molecular oxygen (base pressure 2 Â 10 À10 torr) or in presence of molecular hydrogen with a pressure up to 10 À6 torr negligible photo-reaction occurred. Fitting the observed decay of ethoxides upon irradiation with a Langmuir-type analysis, as a function of gas phase molecular oxygen, the binding constant of the later was found equal to ca. 2 Â 10 7 torr À1 . This value, together with the initial surface coverage of ethoxide of 0.5 with respect to surface Ti atoms, may indicate that the number of adsorbed molecular oxygen needed for maximum reaction rate is similar to that of the free surface Ti atoms.

Microwave-Assisted Modified Polyimide Synthesis: A Facile Route to the Enhancement of Visible-Light-Induced Photocatalytic Performance for Dye Degradation

“…The photocatalytic performances of the synthesized polymers, apropos of RR 120 degradation, were extensively examined (Figure S7a). Herein, the dye decolorization efficiency of commercial WO 3 (band gap 3 eV) was only 49% and was marginally higher than that of pristine PI (44%). , Figure S7b exhibits the structure of RR 120. Following the increase in SWO 3 loading, the visible-light-driven photocatalytic performance of SWO 3 /PI witnessed a progressive enhancement, possibly owing to the considerable improvement brought about in its major attributes, which include crystallinity, visible-light absorption, and charge separation efficiency.…”

Photoreaction of Au/TiO2 for hydrogen production from renewables: a review on the synergistic effect between anatase and rutile phases of TiO2

“…Photoreaction/oxidation of alcohols, carboxylic acids, acetaldehyde and acetone as well as for smaller molecules such as H 2 O, O 2 and CO over the single crystal rutile TiO 2 (110) surface has been studied. Most of these results have been discussed in recent reviews [5][6][7][8][9]. Other recent reviews on photoreaction of powder systems are available and these include those of references [10,11].…”