Theoretical investigation on water adsorption conformations at aqueous anatase TiO₂/water interfaces

Abstract

The interaction of water with TiO2 plays an important role in electrochemistry, geochemistry and environmental science. Yet, whether water spontaneously dissociates on the defect-free TiO2 surface is still in dispute....

Understanding high photocatalytic activity of the TiO2 high-pressure columbite phase by experiments and first-principles calculations

“…The water-splitting reaction energy barriers calculated for columbite (101) confirm the high surface activity of this high-pressure phase for water splitting. Table 2 presents the values reported for energy barriers for different TiO 2 slabs of anatase and rutile 16–18,46–51 and compares them with that for the columbite phase. Comparatively, the energy barrier for water splitting of columbite slab (101) is smaller than those reported for the active slabs of anatase and rutile.…”

“…Oxygen vacancies, especially on the surface are considered highly reactive sites which can enhance photon absorption, photogenerated electron–hole separation, chemical adsorption, reactant molecule activation and ionic conductivity. 7,16,38–40,46,47,51 The effect of oxygen vacancies in anatase and rutile was extensively studied earlier; 16,37–43,47,52–54 however, few studies were conducted to clarify the effect of oxygen vacancies on the high-pressure columbite phase. The theoretical calculations in this study confirm that oxygen vacancies in both anatase and columbite can narrow the optical bandgap by merging the defect states with the conduction band.…”

“…It is concluded that a combination of a high-pressure phase and oxygen vacancy generation is essential to achieve good light absorbance in TiO 2 . Based on the oxygen vacancy formation energy summarized in Table 2, vacancy formation in columbite is energetically more favorable compared to that in the anatase phase, 16–18,46–51 and this can be beneficial to develop oxygen-deficient columbite for water splitting.…”

“…Moreover, the (101) surface of columbite shows a lower energy barrier for water splitting compared to the active surfaces of anatase and rutile, as summarized in Table 1. 16–18,46–51 Taken together, a combination of high light absorbance and chemical absorbance and surface activity is responsible for the high activity of oxygen-deficient columbite. Although oxygen vacancies in bulk may act as recombination centers for charge carriers, 6,7,48,55 the presence of surface oxygen vacancies, multiple phases and formation of heterojunctions after HPT processing are expected to contribute to diminishing the recombination of charge carriers.…”

Band Alignment of 2D Material–Water Interfaces

“…Recent studies have modeled the explicit solid–water interfaces of conventional three-dimensional (3D) materials, ,,− including rutile TiO 2 , ,, anatase TiO 2 , ZnO, CoO, InN, GaN, GaAs, GaP, CdS, SnO 2 , Ta 3 N 5 , BiVO 4 , etc., using density functional theory based molecular dynamics (DFTMD). These studies found that hydration can significantly affect the band alignments of semiconductors.…”