Stability and Electronic Properties of TiO<sub>2</sub> Nanostructures With and Without B and N Doping

Journal Of Physical Chemistry C 113, 12301 - 12308 (2009)

Stability and Electronic Properties of TiO2 Nanostructures With and Without B and N Doping

D.J. Mowbray, J.I. Martínez, J.M. García-Lastra, K.S. Thygesen, K.W. Jacobsen

We address the two main challenges to TiO2-photocatalysis, electron-hole transport and band gap narrowing, by combining nanostructural changes with doping. With this aim we compare TiO2’s electronic properties for small 0D clusters, 1D nanotubes, 2D layers, and 3D bulk phases using different approximations within density functional theory and GW calculations. In particular, we propose a very small (R . 5A° ) but surprisingly stable nanotube structure with promising properties. We find that quantum confinement effects – as expected – generally lead to a widening of the energy gap. However, substitutionally doping with boron or nitrogen is found to give rise to (meta-)stable structures and the introduction of dopant and mid-gap states. Boron is seen to always give rise to n-type doping while depending on the local bonding geometry, nitrogen may give rise to n-type or p-type doping. For undercoordinated TiO2 surface structures found in clusters, nanotubes, and layers N gives rise to acceptor states while for larger clusters and bulk structures donor states are introduced.

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