Energy Band Alignment between Anatase and Rutile TiO2

Using photoelectron spectroscopy, the interface formation of anatase and rutile TiO2 with RuO2 and tin-doped indium oxide (ITO) is studied. It is consistently found that the valence band maximum of rutile is 0.7 +/- 0.1 eV above that of anatase. The alignment is confirmed by electronic structure calculations, which further show that the alignment is related to the splitting of the energy bands formed by the 0 2p(z), lone-pair orbitals. The alignment can explain the different electron concentrations in doped anatase and rutile and the enhanced photocatalytic activity of mixed phase particles.