Modification of TiO₂ with hBN: high temperature anatase phase stabilisation and photocatalytic degradation of 1,4-dioxane

Abstract

This paper examines the modification of anatase TiO 2 with hexagonal boron nitride (hBN) and the impact this coupling has on the temperature of the anatase to rutile phase transition and photocatalytic activity. All samples were 100% anatase when calcined up to 500°C. At 600°C, all BN-modified samples contain mixed rutile and anatase phases, with 8% and 16% BN-TiO 2 showing the highest anatase contents of 64.4% and 65.5% respectively. The control sample converted fully to rutile at 600°C while the BN modified sample converted to rutile only at 650°C. In addition to TiO 2 phase composition, XRD also showed the presence of bulk boron nitride peaks, with the peak at 26°i ndicating the graphite-like hBN structure. Density functional theory calculations of hBN-rings adsorbed at the anatase (101) surface show strong binding at the interface; new interfacial bonds are formed with key interfacial features being formation of B-O-Ti and N-Ti bonds. Models of extended hBN sheets at the anatase (101) surface show that formation of B-O and N-Ti bonds along the edge of the hBN sheet anchor it to the anatase surface. 16% BN-TiO 2 at 500°C showed a significant increase in the photocatalytic degradation of 1,4-dioxane when compared with pure anatase TiO 2 at 500°C. This arises from the effect of hBN on anatase. The computed density of states (DOS) plots show that interfacing anatase with BN results in a red shift in the TiO 2 energy gap; N-p states extend the valence band maximum (VBM) to higher energies. This facilitates transitions from high lying N-p states to the Ti-d conduction band. A simple photoexcited state model shows separation of electrons and holes onto TiO 2 and BN, respectively, which promotes the photocatalytic activity.

Mo doped TiO2: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

“…These results suggest that the excess charge occupies the vacancy site rather than localising at only the Mo and Ti ions ( figure 1(b)). Typically, Ti 3+ ions exhibit computed Bader charges of 10.0-10.5 electrons and spin magnetisations of 0.8-1.0 μ B [23,62]. The values computed for the partially reduced Ti ion in the present work are consistent with our previous study of In-doped TiO 2 [59].…”

Modification of TiO2 with Metal Chalcogenide Nanoclusters for Hydrogen Evolution

“…The negative adsorption energies indicate that the modifiersurface interaction is favourable and the magnitudes of these energies suggest that the nanoclusters are strongly bound at the surface. [32,33,41,42,53] For Sn4S4-r110, shown in From these data, we can see that the Ti-S bonds are shorter than the Ti-Se bonds. This is expected as Se has a larger ionic radius than S. [8,10] Nanocluster metal-S bonds are also shorter than metal-Se bonds, both in the gas-phase and after adsorption at the rutile TiO2 surface.…”

Surface Modification of Rutile TiO2 with Alkaline-Earth Oxide Nanoclusters for Enhanced Oxygen Evolution

“…Previous work on modified metal oxide surfaces shows that key properties determining the chemistry of these structures are not sensitive to the precise adsorption structure of the modifiers at the surface. The properties of the modified surface are consistent as long as the nanocluster modifier binds with the surface through new interfacial bonds, that is, new bonds that form between cations and anions on the surface and nanocluster . To explore this, we analyzed in detail a less stable Mg 12 O 12 -r110 geometry (Figure S4a) for which the results are discussed in the SI.…”

“…The properties of the modified surface are consistent as long as the nanocluster modifier binds with the surface through new interfacial bonds, that is, new bonds that form between cations and anions on the surface and nanocluster. 63 To explore this, we analyzed in detail a less stable Mg 12 O 12 -r110 geometry (Figure S4a) for which the results are discussed in the SI. This analysis shows that there are small quantitative, but not qualitative, differences in the computed properties, so that the sensitivity to the precise structure is not significant.…”