Yongfa Zhu1

1, Tsinghua University, Beijing, , China

Surface electronic density of states can be adjusted via surface structure such as surface vacancies, surface hybrid and ligands. The density of states (DOS) of the photocatalysts valence band (VB), can be regulated and controlled by the structure, number and the kind of surface oxygen vacancies, which can be contributed to the narrowed the band gap and the broaden the VB, thus promoting the separation efficiency of photoinduced electron-hole pairs, and improving the photocatalytic activity. In addition, the theory calculation indicates that the influence of surface oxygen-defect states on the band structure, the DOS of the VB, photoabsorption performance and oxidation-reduction potential for photocatalysts. A variety of technologies were utilized to reveal the physical structure of surface defects and bulk defects, and to display the external relations of defect states with the photodegradation process and the photocurrent, and to imply the inherent law of defect states with the separation and transfer of the photoinduced electrons. This work discovers the promotion mechanism of surface oxygen vacancies on the separation of photoinduced electron-hole pairs, thus new high activity photocatalysts were prepared successfully. In a word, it is beneficial to further understand the relationship of surface oxygen defects with the enhanced separation and transfer of photoinduced electrons, and it has a promoting role in the development of physics and chemistry. The photocatalytic performances of ZnO, BiPO4 and Bi2WO6 photocatalysts have been enhanced greatly via surface oxygen-vacancy.
The surface hybridization on photocatalyst by using the rapid electron and hole transpoting property of delocalized conjugated π materials, on a purpose of enhancing the transportation and the separation of the photocarriers. Therefore, the photocatalytic activity of semiconductor would be increased. The synergic effect between conjugated π materials and photocatalysts such as TiO2,ZnO, Bi2WO6,BiPO4 etc were elucidated. In photocatalysis, the holes in the valence band of ZnO and Bi2WO6 could directly transfer to the HOMO orbital of C3N4, making charge separation more efficient and leading to an enhanced photocatalytic activity. The photocorrosion of ZnO was caused by photogenerated holes, the rapid transportion of holes from ZnO to C3N4 could effectively suppress the photocorrosion of ZnO. Under visible light irradiation, the excited electron from HOMO to LUMO orbital of C3N4 could directly inject into the conduction band (CB) of ZnO, making C3N4/ZnO present a dramatic visible light photocatalytic activity.

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