Site Competition during Coadsorption of Acetone with Methanol and Water on TiO₂(110)

Abstract

The competitive interaction between acetone and two solvent molecules (methanol and water) for surface sites on rutile TiO(2)(110) was studied using temperature-programmed desorption (TPD). On a vacuum-annealed TiO(2)(110) surface, which possessed ~5% oxygen vacancy sites, excess methanol displaced preadsorbed acetone molecules to weakly bound and physisorbed desorption states below 200 K. In contrast, acetone molecules were stabilized on an oxidized surface against displacement by methanol through formation of acetone diolate species. The behavior of acetone with methanol differs from the interactions between acetone and water which are less competitive. Examination of acetone + methanol and acetone + water multilayer combinations shows that acetone is more compatible in water-ice films than in methanol-ice films, presumably because water has greater potential as a hydrogen-bond donor than does methanol. Acetone molecules displaced from the TiO(2)(110) surface by water are more likely to be retained in the near-surface region, in turn having a greater opportunity to revisit the surface, than when methanol is used as a coadsorbate.

Gas‐phase oxidation of 2‐propanol over Au/TiO2 catalysts to probe metal–support interactions

“…This observation points to a deactivation of TiO 2 , presumably due to the exposure to water vapor produced during the co-feeding experiment. It was reported that for acetone adsorption on TiO 2 water has an inhibiting effect [86]. It seems reasonable to assume that during 2-propanol oxidation over TiO 2 water blocks the active sites for oxidation and, as a result, less oxidation to acetone takes place.…”

UHV-FTIRS studies on molecular competitive adsorption:12CO,13CO and CO2on reduced TiO2(110) surfaces

“…Such site competition between two or more adsorbates can suppress reaction rates and thus alter reaction pathways. 3 Therefore, a molecular level understanding of the competition phenomena of the reactants, intermediates and/or products around the active sites on the catalyst surfaces is a fundamentally crucial aspect in elucidating the heterogeneous catalytic reaction mechanisms and thus guiding the design of new catalysts and catalytic reactions. [4][5][6] Due to the excellent properties in heterogeneous catalysis, titanium dioxide (TiO 2 ) has attracted considerable attention in many fields, such as photo-induced water splitting, air purification and solar fuel cells in the last few decades.…”

“…8,9 Studies on competitive adsorption onto TiO 2 (110) at the atomic or molecular scale under ultra-high vacuum (UHV) conditions provide an excellent benchmark for understanding the more complex, realworld heterogeneous catalytic reactions. 2,3,10 Shen and Henderson studied the site competition during co-adsorption of acetone with methanol and water onto TiO 2 (110) by using temperature programmed desorption (TPD). 3 Smith et al investigated the adsorption, desorption, and displacement kinetics of H 2 O and CO 2 on TiO 2 (110) and pointed out that the relative strength of adsorption is the dominant factor of the competitive adsorption kinetics in their discussions.…”

“…2,3,10 Shen and Henderson studied the site competition during co-adsorption of acetone with methanol and water onto TiO 2 (110) by using temperature programmed desorption (TPD). 3 Smith et al investigated the adsorption, desorption, and displacement kinetics of H 2 O and CO 2 on TiO 2 (110) and pointed out that the relative strength of adsorption is the dominant factor of the competitive adsorption kinetics in their discussions. 10 As the simplest and prototypical oxidation reaction on TiO 2 (110), photooxidation of carbon monoxide to carbon dioxide (CO + O 2 -CO 2 ) has been extensively investigated, and some discussions of intrinsic reaction processes are also involved.…”

Strain dependence of dissociative adsorption of H2O on epitaxially strained, out-of-plane polarized, BaTiO3(001) thin films

“…Figure 6(a) compares the TPD spectra of the 8, 15 and 30 nm films. The TPD data show a two stage water desorption process, one at low temperature (around 100-120 • C) and the second, more important stage with a strain dependent onset between 315 and 350 • C. This is clear evidence for the presence of dissociatively adsorbed water on the surface whereas the smaller proportion of physisorbed molecular water is desorbed at 100-120 • C [15,16]. Similar desorption features are observed for the three films except for a variation in the onset of the main peak.…”