Titanium dioxide materials have been studied intensively and extensively dueto photocatalytic applications. A long-standing open question is the energyband alignment of rutile and anatase TiO2 phases, which can affect thephotocatalytic process in the composite system. There are basically twocontradictory viewpoints about the alignment of these two TiO2 phases supportedby respective experiments: 1) straddling type and 2) staggered type. In thiswork, our DFT plus U calculations find that the perfect rutile (110) andanatase (101) surfaces have the straddling type band alignment, whereas thesurfaces with defects can turn the band alignment into the staggered type. Theelectric dipoles induced by defects are responsible for the reversal of bandalignment. Thus the defects introduced during preparations and post-treatmentprocesses of materials are probably the answer to above open question regardingthe band alignment, which can be considered in real practice to tune thephotocatalytic activity of materials.
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