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

This paper examines the modification of anatase TiO 2 with hexagonal boron nitride ( h BN) 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° indicating the graphite-like h BN structure. Density functional theory calculations of h BN-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 h BN sheets at the anatase (101) surface show that formation of B–O and N–Ti bonds along the edge of the h BN 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 h BN 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.