Dear Prof. Moisés Canle López,

I think I didn't ask it clearly. Actually the band gap energy of coupling semiconductor is lower than TiO2. The conduction band edge potential of coupled semiconductor is higher than that of TiO2 and the valance band edge potential of coupled semiconductor is lower than that of TiO2. Under visible light irradiation electron-hole pairs are created in low band semiconductor. In this case, I dont know whether these electrons or holes will move to TiO2 or not. I am waiting for your reply

Do you mean such a system? As much as I remember, it is called Z-scheme. (See attached picture)

Please see the attached picture for more information.In this case, I dont know whether these electrons or holes will move to TiO2 or not

I think it is very unprobable, because the VB of TiO2 is populated.

Under visible light irradiation, the energy of the excitation light is sufficient to directly excite the coupled SC and it is large enough to yield a higher energy level of TiO2 portion of the photocatalyst. According to the band edge position, an artificial Z-scheme mechanism can be suggested for SC/TiO2 system.

Dear Dr. Sridhar Sampath

In heterojunction formation between TiO2 and the other semiconductors, one should consider possible n-n or p-n heterojunctions between TiO2 (as n-type semiconductor) and the second semiconductor (n or p-type). For example, please refer to the attached paper about TiO2/Ag2CrO4 with n-n heterojunction.