Structure of a model TiO2 photocatalytic interface

Abstract

The interaction of water with TiO is crucial to many of its practical applications, including photocatalytic water splitting. Following the first demonstration of this phenomenon 40 years ago there have been numerous studies of the rutile single-crystal TiO(110) interface with water. This has provided an atomic-level understanding of the water-TiO interaction. However, nearly all of the previous studies of water/TiO interfaces involve water in the vapour phase. Here, we explore the interfacial structure between liquid water and a rutile TiO(110) surface pre-characterized at the atomic level. Scanning tunnelling microscopy and surface X-ray diffraction are used to determine the structure, which is comprised of an ordered array of hydroxyl molecules with molecular water in the second layer. Static and dynamic density functional theory calculations suggest that a possible mechanism for formation of the hydroxyl overlayer involves the mixed adsorption of O and HO on a partially defected surface. The quantitative structural properties derived here provide a basis with which to explore the atomistic properties and hence mechanisms involved in TiO photocatalysis.

Diffusion and reaction pathways of water near fully hydrated TiO2 surfaces from ab initio molecular dynamics

“…Water dissociation on defect-free rutile (110) is a long-standing debate within the scientific community. 42,43,45,46,70,71 For each surface, we analyze the hydration layer structure with a threedomain model that differentiates water molecules based on lateral mobility and orientation freedom. Surface reactivity is analyzed at full hydration (and compared to neardry conditions), and graph theory is used to connect water reaction pathways to TiO 2 surface structures under ambient conditions.…”

Engineering oxygen vacancy on rutile TiO2 for efficient electron-hole separation and high solar-driven photocatalytic hydrogen evolution

“…Hence, photocatalytic hydrogen production attracts much more attention recently [2][3][4]. Since Fujishima and Honda [5][6][7] discovered hydrogen production from water splitting on TiO 2 for the first time, it is considered as the most promising photocatalyst candidate due to nontoxicity, high stability and low-cost [8][9][10]. Therefore, TiO 2 is widely used in photocatalytic degradation of pollutants, photocatalytic hydrogen production, solar cells, photoelectrochemical devices, and so on [11][12][13][14].…”

Dynamic Stabilization of Metal Oxide–Water Interfaces

“…Surface pKa prediction based on bond valence analysis suggests that water exchange will influence the proton transfer reactions underlying the acid/base reactivity at the interface. Our findings provide important new insights for understanding complex interfacial chemical processes at metal oxide-water interfaces.The interfaces between metal oxides and water are among the most important in nature and in emerging energy applications, with wide ranging impacts from photocatalytic water splitting [1][2][3][4] to the geochemical cycling of elements 5,6 . Key chemical processes such as adsorption, electron transfer, growth, and dissolution all depend principally on the atomic structure adopted at these interfaces.…”

“…Simulations suggest that movement of overlying water molecules can play an essential role in stabilizing the interface and influencing its chemical behavior 14,15 . However, simulated [14][15][16][17] or spectroscopically probed 18 dynamics are seldom integrated with experimentally derived interface structure models to achieve comprehensive insight into interfacial structure 4 . To understand and predict chemical processes at dynamically active metal oxide-water interfaces, structure and dynamics must be considered as a unified whole.…”

“…However, rigorous ab initio modeling can reveal dynamical behavior underlying time-averaged data which may not be interpretable using static structural models 23 . Sub-picosecond phenomena at metal oxide-water interfaces, including ligand exchange and proton dynamics, are within reach of accurate density functional theory-based molecular dynamics (DFT-MD) 4,[15][16][17] .…”