Photocatalysis is one of the important methods to solve the current environmental pollution and energy crisis. However, the photocatalytic efficiency of most photocatalysts is still low. Improving the separation of photogenerated charges is an effective way to enhance the photocatalytic efficiency. Firstly, the paper summarizes the photocatalysis mechanism, and then reviews the effects of built⁃in electric field in semiconductor p⁃n junction, heterophase junctions, polarized surfaces and ferroelectric material polarization on separation efficiency of photogenerated charges and photocatalytic performance, based on the recent domestic and international research progress in improving the separation efficiency of photogenerated charges. Finally, the future development of built⁃in electric field in photocatalysis is prospected.

A two⁃dimensional nano flake rutile titanium dioxide (TiO ₂) semiconductor material was synthesized under low temperature by hydrothermal method.The effects of HCl concentration on the crystalline phase,crystallinity,morphology,particle size and photoelectric properties of obtained TiO ₂ particles are studied using XRD,SEM and SPV.The results indicate that the micron spherical,nanosheets and nanorods rutile TiO ₂ particles can be synthesized by controlling the HCl concentration at 3,5,7 mol/L,respectively.Moreover,the photocatalytic performance of obtained rutile TiO ₂ particles is further investigated by degradation of rhodamine B. The results show that the activities of micron spherical,nanosheets and nanorods rutile TiO ₂ samples are higher than that of traditional rutile TiO ₂ sample obtained by calcination method.Compared with micron spherical and nanorods rutile TiO ₂ samples,2D nanosheets rutile TiO ₂ sample has better photocatalytic properties.SPV results reveal that the 2D nanosheets rutile TiO ₂ has a significant efficiency on photogenerated charges separation and migration.