Research On Photocatalytic Enhancement Of Semicondutors Via π-conjugate Molecule Hybridization

Developing novel photocatalysts with high photocatalytic efficiency,visible-light active and high stability is of great importance for photocatalysisresearch. The thesis developed a surface modification on photocatalyst by using therapid electron and hole transpoting property of delocalized conjugated Ï€ materials, ona purpose of enhancing the transportation and the separation of the photocarriers.Therefore, the photocatalytic activity of semiconductor would be increased. TiO₂,ZnO, Bi₂WO₆are the three kinds of typical semiconducting photocatalysts. Thesynergic effect between conjugated Ï€ materials and TiO₂(ZnO, Bi₂WO₆) and thepossible mechanisms of enhancement of photocatalytic activity via hybridizationwere also systematically investigated. Moreover, the application of conjugated Ï€material hybridized photocatalyst in photoelectric catalytic degradation was alsoinvestigated.C₃N₄/ZnO and C₃N₄/Bi₂WO₆hybrid photocatalysts were obtained by a facilechemisorption approach. The photocatalytic activity of ZnO and Bi₂WO₆wasdramatically enhanced via C₃N₄hybridization. Monolayer C₃N₄hybridizedphotocatalysts had optimal photocatalytic activity, the photocatalytic activity ofC₃N₄/ZnO and C₃N₄/Bi₂WO₆were increased by3.5times and70%, respectively. Inphotocatalysis, the holes in the valence band (VB) of ZnO and Bi₂WO₆coulddirectly transfer to the HOMO orbital of C₃N₄, making charge separation moreefficient and leading to an enhanced photocatalytic activity. The photocorrosion ofZnO was caused by photogenerated holes, the rapid transportion of holes from ZnO toC₃N₄could effectively suppress the photocorrosion of ZnO. Under visible lightirradiation, the excited electron from HOMO to LUMO orbital of C₃N₄could directlyinject into the conduction band (CB) of ZnO, making C₃N₄/ZnO present a dramaticvisible light photocatalytic activity.Graphene was a good electron acceptor and transporter due to itstwo-dimensional conjugated Ï€ structure; graphene-like carbon/TiO₂(GT) hybrid photocatalysts were prepared via an in-situ graphitization approach. Monolayergraphene hybridized TiO₂photocatalyst had optimal photocatalytic activity, thephotocatalytic activity of GT photocatalyst was increased by2.5times. Inphotocatalysis, the excited electrons of TiO₂could transfer to graphene-like carbon,making charge separation more efficient and leading to an enhanced photocatalyticactivity.PANI/TiO₂hybrid film was prepared via a facile chemisorption approach. Thebest photoelectrocatalytic degradation efficiency of2,4-DCP with the PANI/TiO₂film was acquired at an external potential of1.5V with a layer of1nm thick PANI.The generated holes in VB of TiO₂can directly transfer to the HOMO level of PANIand the electrons can transfer to the other side of the system via the external circuit.Accordingly, a rapid photogenerated charge separation was achieved, whichsignificantly enhanced the photoelectrocatalytic activity of the PANI/TiO₂films.