Short Hydrogen Bonds at the Water/TiO₂ (Anatase) Interface

Abstract

The nature of peculiar, short H bonds formed by water molecules in contact with the (101) anatase surface and their effects on the structural and vibrational properties of the first water layers adsorbed on the same surface have been investigated by performing density functional theory (DFT) total energy calculations and ab initio molecular dynamics (AIMD) simulations at different temperatures. Present results show that these short H bonds originate from a water/anatase interface effect related to an electronic charge transfer from surface Ti atoms to surface O atoms, mediated by water molecules. Further, AIMD simulations performed at low temperature indicate that such short H bonds are at the ground of both the atomic arrangements of the water layers and the peculiar features appearing in the corresponding vibrational spectra. The same interface effect significantly influences also the atomic arrangements and the vibrational properties of intermediates of the O 2 photoreduction reaction, which turn out to be involved in similar charge transfer processes as well as in the formation of short H bonds. AIMD simulations show that these short H bonds are still present at room temperature and give estimates of the vibrational frequencies of the same intermediates, which are in a quite good agreement with the experimental findings. Such an agreement supports the unifying theoretical picture proposed here for water molecules and O 2 photoreduction intermediates in contact with the anatase surface.

A surface science perspective on TiO2 photocatalysis

“…They observed that this reaction occurred at more negative potentials for A TiO 2 (001). This was linked to a more negative flatband potential for A TiO 2 (001) (by 0.06 V) that the authors attributed to a greater ability of this surface to thermally dissociate water in comparison with the A TiO 2 (101) surface [1681][1682][1683][1684]. As mentioned above, the (001) surface is a rough-and-trough reconstructed structure possessing (4×1)/(1×4) order.…”

“…Fundamental studies of the chemistry of water (and hydroxyls) on single crystal TiO 2 surfaces provide a starting point for understanding the photochemical properties of this process [853]. Extensive experimental [138,192,194,195,199,527,566,580,792,795,797,799,803,804,807,810,843,852,1681,1683,[1712][1713][1714][1715][1716][1717] and theoretical [193,522,527,792,810,824,826,830,831,1660,1682,1684,1711,1712,[1717][1718][1719] work has been invested in understanding the molecular-level interactions of water with single crystal TiO 2 surfaces. This author is unaware of any reports to date in which photochemical water splitting (in either half reaction) was performed on a single crystal TiO 2 surface under UHV conditions.…”

Bifunctional ultraviolet/ultrasound responsive composite TiO2/polyelectrolyte microcapsules

“…), and protects them against movement, see Figure 4b. 16,[29][30][31][32][33] The attractive potential between the sulfonated monolayers and TiO 2 nanoparticles by van der Waals forces, which could be predicted using the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory, also promoted this interaction process. 26,27 As a consequence the formed NPs were firmly mixed and combined together with PEs in assist of these potential interaction.…”

Diffusivity and Mobility of Adsorbed Water Layers at TiO2 Rutile and Anatase Interfaces

“…For instance, Inelastic Neutron Scattering (INS) measurements have led to vibrational spectra of adsorbed water on anatase powder and rutile rods [6,7]; this led to insight that confined adsorbed water molecules have dynamical and vibrational behaviour more redolent of less mobile ice vis-à-vis to a liquid [6,7]. This adsorbed-water vibrational behaviour has been studied in detail via molecular dynamics (MD) at interfaces of anatase-(101) and rutile-(110) with water [8,9]. Further, ab initio MD (AIMD) has led to important results in interesting studies recently [9,10] on librational and higher-frequency adsorbed-water modes.…”