3, University College London, London, , United Kingdom
2, Imperial College London, London, , United Kingdom
The use of doped TiO2 as a photocatalyst in water splitting for hydrogen production continues to demonstrate significant potential in renewable energy technology devices. We characterised the behaviour, nature and spatial location of non-metal ion dopants in the TiO2 matrix. To create a stable dopant distribution profile that can be probed in the 3D space, single crystal substrate forms of TiO2 were used.
We investigated the diffusion of nitrogen, sulphur, carbon and boron dopants into TiO2 (110), (100), (001) substrates using a novel high temperature method. The former three dopants were found to be in interstitial and substitutional sites with a concentration gradient into the bulk, as measured by the Thermoscientific (K-alpha & Theta probe) X-ray photoelectron spectroscopy.
We also report the growth of a TiBO3 phase (at least 20nm thick) in multiple orientations, different to that of the TiO2 (110) substrate. XRD has confirmed a film-like layer of TiBO3 on the TiO2 surface whilst Raman spectroscopy has shown potential uniform growth of TiBO3 on the TiO2 (100) and (001) surfaces but not on the TiO2 (110) surface. Reciprocal space maps revealed the orientation of the TiBO3 layer.
Whilst the ability to grow thick films of TiBO3 is crucial for the advancement of facile film growth technology, fundamental insight into dopant diffusion gradients is significant for the investigation of structure-function relationship, essential for designing materials with optimised photoactivity.