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Research on Photocatalytic Enhancement of Semicondutors Via π-conjugate Molecule Hybridization

Author: WangYaJun
Tutor: ZhuYongFa
School: Tsinghua University
Course: Chemistry
Keywords: π-conjugate molecule nano-semiconductors surfacehybridization photocatalysis photocorrosion
CLC: O643.32
Type: PhD thesis
Year: 2011
Downloads: 201
Quote: 0
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Abstract


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 π 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 π materials and TiO2（ZnO, Bi2WO6） and thepossible mechanisms of enhancement of photocatalytic activity via hybridizationwere also systematically investigated. Moreover, the application of conjugated πmaterial 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 π 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.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalytic reaction
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