| TiO2 nanotube arrays (NTAs) with unique 3D tubular structure have excellent absorption property and well UV light response, which have been widely used in photocatalytic field. But the narrow light response range and large electron-hole pair recombination probability are still problems which need to be solved. In this study, TiOz NTAs were prepared by anodic oxidation method, then narrow band gap semiconductor (CdS-CdSe) and metal (Pt) co-modified TiO2 NTAs were prepared by multiple deposition technology. The CdSe/CdS/Pt -TiO2 NTAs show improved visible light photocatalytic properties.First, TiO2 NTAs were prepared by electrochemical anodization method, then TiO2 NTAs were used as the substrate, Pt, CdS and CdSe nanoparticles (NPs) were deposited onto the surface of TiO2 NTAs through photoreduction deposition, chemical bath deposition, and electrodeposition method respectively. The relative amounts of Pt, CdS and CdSe NPs were controlled by adjusting the H2PtCl6 concentration, deposition cycle of CdS and deposition time of CdSe, the controllable deposition of Pt, CdS and CdSe NPs was realized. The samples were characterized by XRD, SEM, EDS, XPS, TEM, UV-Vis methods, and the degradation of methyl orange (MO) and dynamics analysis of samples were also conducted. The influence of the various deposition process parameters on the microstructure and photocatalytic properties of modified TiO2 NTAs was analysed. The different performance of CdS/Pt/TiO2, CdSe/CdS/TiO2, CdSe/CdS/Pt/TiO2 NTAs and single Pt, CdS or CdSe NPs modified TiO2 NTAs was researched. The transmission path of photo-generated electron in the composite structure was discussed.XRD, EDS and XPS results show that:Pt, CdS and CdSe have been deposited onto TiO2 nanotubes, and Pt is in the elemental state. SEM and TEM observation displayed that the size of these nanoparticles were about 40 nm,10 nm and 6 nm, respectively. The results of UV-Vis and visible light photocatalytic showed that the visible light absorbance of the co-modified CdS/Pt/TiO2 and CdSe/CdS/TiO2 NTAs are the superposition of the visible light absorbance of Pt/TiO2, CdS/TiO2 NTAs and CdS/TiO2, CdS/TiO2 NTAs, respectively. Although CdSe/CdS/Pt triple modified TiO2 NTAs has a strong absorption in the visible light region, and in the visible light range of 400 to 600 nm absorption enhancement is obvious, but the visible light photocatalytic activity decreases slightly. The photodegradation rate of CdS/Pt/TiO2 and CdSe/CdS/TiO2 NTAs to MO solution after being irradiated for 2 h under visible light can reach the maximum,91.9% and 96.0%, respectively. After being reused for 15 times, the photodegradation rate of CdS/Pt/TiO2 and CdSe/CdS/TiO2 NTAs still can reach 91.7% and 84.3%. Under visible light irradiation, the photodegradation rate of MO for CdSe/CdS/Pt/TiO2 NTAs is only 92.8% after being irradiated for 2 h, which has not reach the highest value. Excessive deposition of nanoparticles reduced effective area of receiving light and space for photocatalytic process, so the deposition process need to be optimized further.In this study, the controllable deposition of narrow band gap semiconductors CdS and CdSe were adopted to expand the light response to visible light region, and the deposition of Pt NPs were adopted to promote photogenerated electron-hole pair separation, nanoscale construction was realized by controlling the microstructrue of the material. The CdSe/CdS/Pt/TiO2 NTAs with superior visible light photocatalytic properties was obtained by the two mechanism works synergistically. The deposition model was established and the path of visible light activated charge transfer was also analyzed, which provide theoretical basis and technical support for the preparing of new nano-TiO2 photocatalytic materials. |
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