关键词: 锐钛矿, 价带顶, 导带底, 电子能级排列, 密度泛函理论

Abstract:

As one of the most commonly-used materials for photocatalysis and solar energy conversion, titanium dioxide (TiO₂) has been extensively studied for more than 40 years. Its photoelectrochemical activity crucially depends on the band positions at the interface. In this work, the valence band maximum (VBM) and conduction band minimum (CBM) of a model TiO₂ surface are computed using the standard work function method at the level of Perdew-Burke-Ernzerhof (PBE) density functional, which are then converted to the scale of the standard hydrogen electrode (SHE) by subtracting the absolute SHE potential. Comparing with the rutile TiO₂(110) surface, we find a similar upshift in the VBM and CBM upon the adsorption of water molecules on the anatase TiO₂(101) surface, and the band gap error intrinsic to the PBE functional can be mainly attributable to mis-positioning of the VBM. In addition, in contrast to the finding on the rutile TiO₂(110) surface that the adsorption of 1 monolayer water largely recovers the band alignment of the aqueous interface, our preliminary calculations indicate that on the anatase TiO₂(101) surface there is a considerable difference between the simplified model with the adsorption of 1 monolayer water and the fully solvated interface, suggesting the necessity to include the water molecules beyond the first adsorption layer in order to realistically represent the anatase TiO₂ water interface.

Key words: anatase, valence band maximum, conduction band minimum, band alignment, density functional theory