Preparation Of CdSe And Pt Modified TiO₂Nanotube Arrays And Its Visible Light Photocatalytic Performance

In this study, TiO2NTAs were prepared by electrochemical anodization method, andthe influence of electrolyte concentration, anodic oxidation voltage, oxidation time onthe microstructure of material was studied. Then using TiO2NTAs as the substrate,narrow band gap semiconductor cadmium selenide (CdSe) were deposited onto thesurface of TiO2NTAs through electrodeposition method, and the deposition of the CdSewas controlled by adjusting the electrodeposition electrolyte concentration,electrodeposition time. Furthermore, in order to improve the quantum efficiency of TiO2NTAs, co-modification was conducted for TiO2NTAs, noble metal Pt were depositedonto the TiO2NTAs firstly, and then CdSe nanoparticles were deposited on TiO2NTAsafter Pt modification. The samples were characterized by XRD, SEM, EDS, XPS, TEM,UV-vis methods, and the degradation of methyl orange of samples was also tested. Theinfluence of the various deposition process parameters on the microstructure andphotocatalytic properties of modified TiO2NTAs was analysised. The differentperformance of Pt and CdSe co-modified TiO2NTAs and single Pt or CdSe modifiedTiO2NTAs was researched. The transmission path of photo-generated electron in thecomposite structure was discussed and the the photocatalytic reaction model wasestablished.The results show that: TiO2NTAs prepared by anodic oxidation method presentshighly ordered tubular structure. The tube length and tube gap were affected by watercontent in the electrolyte obviously, tube length changers in the range of16.5μm~4μm, while the tube gap changed from0mm to22mm; The studies on electrochemicaldeposition of CdSe indicate that the amount and size of CdSe nanoparticles wasinfluenced by electrodeposition time, electrolyte concentration and intertube spaces.With the increasing of electrolyte concentration and electrodeposition time, intertubespaces became smaller, the aggregation of CdSe nanoparticles on the mouth of TiO2NTAs become more obvious. The CdSe nanoparticles with the size of15～20nmdistributed uniformly on the surface of TiO2NTAs when deposited in the electrolytecontaining0.02M CdCl2,2mMSeO2and0.02M Na2SO4with time of600s, and watercontent of10vol%. On this condition maximum MO degradation rate can reachedunder visible light (250W halogen lamp) irradiation for120min, which was94.4%forthe CdSe/TiO2NTAs samples. After reused for five times, the degradation rate of MOstill reached about80%, showing good stability and cycling properties of composite photocatalyst. Pt modified TiO2NTAs were prepared by light reduction method. Theresults show that chloroplatinic acid (H2PtCl6) concentration affects the amount anddistribution of deposited particles. Pt nanoparticles distributed evenly on the surface ofPt/TiO2NTAs when prepared in2mM H2PtCl6solution, the size of nanoparticles wasabout10nm. After co-deposition CdSe with eletrodeposition time of400s, the amountof nanoparticles on the surfaces of TiO2NTAs significantly increased, and the particlesize was about15nm. After irradiation under visible light for120min, degradation rateof methyl orange is86.7%. When compared to the single CdSe modified samples, thedegradation rate of co-modified samples was increased by25%. TiO2NTAs exhibitssuperior visible light photocatalytic properties by co-modification of CdSe and Ptnanoparticles.