First-Principles Study of the Water Adsorption on Anatase(101) as a Function of the Coverage

Abstract

An understanding of the interaction of water with the anatase (101) surface is crucial for developing strategies to improve the efficiency of the photocatalytic reactions involved in solar water splitting. Despite a number of previous investigations, it is still not clear if water preferentially adsorbs in its molecular or dissociated form on anatase (101). With the aim of shedding some light on this controversial issue, we report the results of periodic screened-exchange density functional theory calculations of the dissociative, molecular and mixed adsorption modes on the anatase (101) surface at various coverages. Our calculations support the suggestion that surface adsorbed OH groups are present which has been made on the basis of recently measured X-ray photoelectron spectroscopy, temperature programmed desorption and scanning tunnelling microscopy data. It is also shown that the relative stability of water adsorption on anatase (101) can be understood in terms of a simple model based on the number and nature of the hydrogen bonds formed as well as the adsorbate-induced atomic displacements in the surface layers. These general conclusions are found to be insensitive to the specific choice of approximation for electronic exchange and correlation within density functional theory. The simple model of water-anatase interactions presented here may be of wider validity in determining the geometry of water-oxide interfaces.

Reactive molecular dynamics simulations of hydration shells surrounding spherical TiO2nanoparticles: implications for proton-transfer reactions

“…These results are in agreement with previous ReaxFF calculations, 44 but the extent of dissociation (0.72) is much higher in comparison with that obtained for the NPs (∼0.4) which is not expected due to the well-known higher reactivity of the curved surfaces with respect to flat ones. Previous DFT calculations 15 and X-ray photoelectron spectroscopy experiments 60 indicate that a mixed dissociated and undissociated water adsorption takes place, in line with what we found by ReaxFF calculations. However, the relative extent of dissociated water reported is 0.25.…”

“…Finally, we present a comparison of the reactivity of water on curved vs. flat surfaces. We consider the flat anatase (101) surface since it is the most stable anatase surface and has been extensively studied with respect to water reactivity both theoretically [11][12][13][14][15][16][17]63 and experimentally. [18][19][20][21][22][23]64 Much effort was devoted to the understanding of the reactivity of water on this surface, going from low coverage to the full monolayer to interfacing bulk water.…”

“…For this reason, several first-principles studies have investigated the detailed atomistic description of the water chemistry and multilayer dynamical structures on low-index flat surfaces. [11][12][13][14][15][16][17] Also, several recent experimental studies have been carried out to determine the interaction at the interface between water and flat TiO 2 surfaces. [18][19][20][21][22][23] However, in practical applications, TiO 2 is mostly used in the form of nanoparticles, which may partially dissolve and become round-or potato-shape in a diluted aqueous environment.…”

Mildly regulated intrinsic faradaic layer at the oxide/water interface for improved photoelectrochemical performance

“…11 The faradaic layers can accelerate both interface charge collection and oxygen evolution reaction (OER) kinetics and improve the performance of a photoelectrode. [12][13][14][15] Moreover, some recent studies have suggested that there is an intrinsic hydrated layer on the surface of metal oxide in ambient air or an electrolyte, 6,[16][17][18][19] which also has signicant effects on interface charge separation and transfer. [20][21][22] Is it possible that the intrinsic hydrated layer plays the same role with an extrinsic faradaic layer?…”

“…Moreover, some recent studies have suggested that there is an intrinsic hydrated layer on the surface of metal oxide in ambient air or an electrolyte, 6 , 16 – 19 which also has significant effects on interface charge separation and transfer. 20 – 22 Is it possible that the intrinsic hydrated layer plays the same role with an extrinsic faradaic layer?…”