Synthesis And Properties Of Metal-Modified Singlecrystal TiO₂ Photocatalysts

TiO₂ photocatalysts have been widely used in the field of photocatalystic degrading contaminants due to its advantages of photo-corrosion resistance,high reactivity,non-toxicity and low cost.However,the photocatalytic performance of TiO₂-based photocatalyst has been limited by the weak absorption of visible light and the high combination rate of photo-excited carriers,which leads to that complete removal of trace refractory organic pollutants is still a great challenge.To tackle the problem,this dissertation designed and synthesized three metal-modified single-crystal TiO₂ photocatalysts via introduce metallic plasmonic effect and high conductivity of single crystal.The structure-activity relationship between metal modification types and photocatalystic degradation of organic pollutants?tetracycline,4-NP and phenol?was investigated in detail.TEM,SEM,XRD,ESR,MS and EIS were employed to analyze the as-prepared samples,and further combined with free radical trapping experiment to study the mechanism of high efficiency of degrading refractory.The main content was shown as follows:1.The synthesis and properties of Ag-modified single-crystal TiO₂ photocatalystSingle-crystal TiO₂?SCTiO₂?nanorods were synthesized via hydrothermal method,which was followed by loading Ag nanoparticles onto SCTiO₂ surface through photo-reduction method,preparing Ag-SCTiO₂ photocatalyst.The successful preparation of Ag-SCTiO₂ was confirmed by SEM,TEM,XRD,XPS et al.As the results of degrading tetracycline shown,compared with non-modified counterpart,Ag-SCTiO₂ exhibited higher absorption of visible light and enhanced separation of photo-induced charge carriers.Under visible light and artificial sunlight irradiation,the photocatalytic degradation rate of Ag-SCTiO₂ is 2.8 times and 4.2 times higher than that of SCTiO₂,respectively.Furthermore,tetracycline was completely removed over Ag-SCTiO₂photocatalyst within 50 min under artificial sunlight irradiation.2.The synthesis and properties of Bi-modified single-crystal TiO₂ photocatalystIn order to reduce the cost of photocatalyst,cheap metal Bi was employed to substitute for noble metal Ag,namely,Bi-SCTiO₂ photocatalyst was prepared via similar method.As the results shown,under artificial sunlight irradiation,Bi-SCTiO₂ photocatalyst displayed excellent photocatalytic activity,completely degrading tetracycline within 40 min(k=0.0939 min^-1),which is higher than that of Ag-SCTiO₂(k=0.0834 min^-1).Besides,4-NP and phenol were also completely removed within 150 min and 120 min,respectively.However,total removal of 4-NP and phenol is extremely difficult for Ag-SCTiO₂.3.The synthesis and properties of Ag/Bi-modified single-crystal TiO₂ photocatalystDue to the improvement of photocatalytic performance of TiO₂ modified by single component is always limited,in order to further improve the photocatalytic performance of TiO₂,Ag/Bi-SCTiO₂ photocatalyst was synthesized by loading Ag/Bi nanoparticles onto SCTiO₂surface via photo-reduction method.The work function of Bi is lower than that of Ag,resulting in electrons would transfer from Bi to Ag,which accelerates the separation of charge carriers.As the results shown,compared with the single-metal-modified counterparts,AgBi-SCTiO₂photocatalyst shows higher photocatalytic activity,completely degrading tetracycline within 40min(k=0.1226 min^-1),and completely degrading 4-NP(k=0.0432 min^-1)and phenol(k=0.0402 min^-1)within 120 min,respectively.