Fabrication And Functionalization Of TiO₂ Mesocrystals For Photocatalytic Degradation Of Organic Pollutants

Mesocrystals,as a sort of novel material with nano-superstructure,are constructed by oriented alignment of oriented nanocrystals.On account of the unique hierarchical structure,mesocrystals not merely display larger specific surface area and porosity than single crystal,higher crystallinity than polycrystal,but also possess superior charge separation efficiency.Hence,TiO2 mesocrystals behave superior photocatalytic performance than common TiO2 materials.However,the practical application of TiO2 mesocrystals is still restricted by the weak absorbance of visible light,high recombination of photogenerated charges,difficult recovery,non-selectivity in photocatalytic performance and so forth.Considering that the study of mesocrystals is still in infancy,research about the growth mechanism and modification of TiO2 mesocrystals are not enough.Therefore,the investigations of modification and functionalization of TiO2 mesocrystals are highly desired.The works we developed for modification and functionalization of TiO2 mesocrystals are described as follows.(1)Ag nanoparticles deposited graphene oxide-TiO2 mesocrystals(Ag/GO-TMCs)were synthesized using simple photoreduction and active esterification reaction.The unique structure of mesocrystal are well preserved in Ag/GO-TMCs.The surface plasmon resonance of Ag nanoparticle and the large surface area as well as excellent charge transfer efficiency of GO endow the Ag/GO-TMCs composite catalysts superior ability of adsorption and light absorbance,as well as higher separation efficiency of photogenerated electron and hole pairs.As a result,compared with the pristine TiO2 mesocrystals,the adsorption and photocatalytic degradation efficiency of Ag/GO-TMCs toward organic dye Rhodamine B(RhB)have improved by around 5%and 45%,respectively.Besides,the degradation efficiency of Ag/GO-TMCs is still higher than 90%after recycled for 5 times.(2)Reduced graphene oxide supported AgI-TiO2 mesocrystals(AgI-TMCs-rGO)were successfully synthesized by hydrothermal reaction process and in situ deposition-precipitation method.The interaction effects among the AgI,rGO and TiO2 mesocrystals could effectively modify TiO2 mesocrystals and suppress the decomposition of AgI.The results show that 20%AgI-TMCs-rGO displays highest photocatalytic degradation efficiency and reusability among the catalysts under visible light irradiation,and the degradation efficiency of 20%AgI-TMCs-rGO has improved around 40%than pristine TiO2 mesocrystals.(3)A novel synthesis method to prepare magnetic TiO2 mesocrystals composite materials was developed.The magnetic TiO2 mesocrystals composite(Fe3O4/GO-TiO2)was synthesized by the amidation reaction between the amino group of the amino-functionalized Fe3O4 with different morphology and carboxyl group of GO-TMCs.The Fe3O4/GO-TiO2 composite materials are proved to possess superior adsorption,photoelectric conversion efficiency,separation efficiency of photoinduced charges,as well as visible light photocatalytic activity.In addition,the magnetic functional modification endows Fe3O4/GO-TiO2 composite materials convenient recycling performance and repeatability.(4)The novel Pr-doped molecularly imprinted TiO2 mesocrystals(Pr-MIP-TMCs)were successfully fabricated by a facile one-pot solvothermal method with Pr3+ as dopant ion and DNBP(2-sec-butyl-4,6-dinitrophenol)as both template molecule and microstructure-director,and the study of molecularly imprinted TiO2 mesocrystals was done for the first time.The Pr-MIP-TMCs exhibit higher adsorption capacity and greater selectivity for DNBP in the degradation tests of DNBP and DNBP/phenol mixed solution,and possess architecture of TiO2 mesocrystals.2%Pr-MIP-TMCs exhibits about 5 fold higher photocatalytic activity than TiO2 mesocrystals and well reproducibility.