Adsorption of Acetone on Rutile TiO₂: A DFT and FTIRS Study

Abstract

Acetone adsorbed on rutile TiO 2 nanoparticles was investigated with respect to its energetic, vibrational, and chemical properties. Temperature-dependent ultrahigh-vacuum Fourier transform infrared spectroscopy measurements for different acetone dosages (4.5− 900 L) give insights into the acetone adsorption behavior. Those experiments indicate thermal-induced reactions of acetone on rutile TiO 2 surfaces yielding new species. Density functional theory calculations were performed to investigate acetone adsorption on rutile TiO 2 (110). Particularly, the importance of sampling the adsorption configuration space is shown. Adsorption geometries that are energetically significantly more favorable than the commonly used high-symmetry configurations are presented. To facilitate the comparability to the experiment, theoretical infrared spectra were computed using density functional perturbation theory for various acetone adsorption geometries using different exchangecorrelation functionals. Additionally, computational spectra were obtained for several species which are potential products from reactions of acetone on TiO 2 surfaces. The investigated species are η 2 -acetate, η 2 -diolate, η 1 -enolate, and mesityl oxide. For η 1acetone, experimental and calculated spectra fit well for low temperatures, whereas for elevated temperatures, emerging bands indicate the formation of diolate.

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“…The adsorbed acetone then reacts with surface oxygen to form a diolate. The additional bands visible at 1650 and 1600 cm –1 are very close to the bands reported in the literature (1655 and 1595 cm –1 on TiO 2 for the CO and the CC bond, respectively) for mesityl oxide an intermediate for the condensation reaction of acetone. , Although it is impossible to infer all the reaction steps of acetone on the surface of WO 3 , these results indicate that also for this chemically complex gas, the initial interaction between the surface vacancies and the oxygen of acetone plays a crucial role. From there, acetone reacts with WO 3 resulting in the visible decrease in the bands attributed to tungsten–oxygen and the detected decrease in the resistance, see the schematic Figure c.…”

“…This indicates that acetone adsorbs via the oxygen of its carbonyl into the oxygen vacancy of the WO 3 surface. 63,64 Because of the strong decrease in the bands attributed to the tungsten−oxygen bond for the SA sample, only the band attributed to asymmetric deformation of the methyl groups of acetone is visible at a wave number very close to that reported for free acetone. 64 This indicates that the methyl group is not strongly affected by the adsorption of acetone to the surface.…”

“…There is a great deal of the literature which examines the surface adsorption of acetone onto different solids under varying conditions. In the literature, it was found that at lower temperatures, acetone adsorbs through hydrogen bonding with surface hydroxyl groups, while at higher temperatures, the situation is more complicated. , Würger et al reported that the adsorption of acetone onto the surface of TiO 2 via the carbonyl group results in a peak shift of the band attributed to the CO bond . The band attributed to the carbonyl group of free acetone is usually found at approximately 1715 cm –1 , while the band of adsorbed acetone is known to shift to 1680 cm –1 .…”

“…The additional bands visible at 1650 and 1600 cm −1 are very close to the bands reported in the literature (1655 and 1595 cm −1 on TiO 2 for the CO and the CC bond, respectively) for mesityl oxide an intermediate for the condensation reaction of acetone. 56,63 Although it is impossible to infer all the reaction steps of acetone on the surface of WO 3 , these results indicate that also for this chemically complex gas, the initial interaction between the surface vacancies and the oxygen of acetone plays a crucial role.…”

“…61,62 Wurger et al reported that the adsorption of acetone onto the surface of TiO 2 via the carbonyl group results in a peak shift of the band attributed to the CO bond. 63 The band attributed to the carbonyl group of free acetone is usually found at approximately 1715 cm −1 , while the band of adsorbed acetone is known to shift to 1680 cm −1 . 64 In the DRIFT spectra of the SA, in addition to the decreasing bands attributed to tungsten−oxygen, a single broad carbonyl band at 1680 cm −1 is increasing.…”