Synthesis And Photoelectrochemical Properties Of CdTe Nanoparticle-Sensitized TiO₂ Nanotube Arrays

In this paper,a conventional three-electrode potentiostatic system was used for cathodic deposition of CdTe nanotube and nanowire.CdTe nanoparticle-sensitized TiO₂ nanotube arrays（CdTe/TiO₂ NTAs）were prepared by combining the sol-gel method with the electrodeposition method by the aid of anodic aluminum oxide（AAO）template.The morphology,structure and composition of the materials were characterized by scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,energy dispersive X-ray spectroscopy（EDS）and X-ray diffraction（XRD）.The photo response and photocatalytic activity of the materials were investigated by UV-vis absorption spectroscopy.The alkaline medium containing Cd（Ac）₂?2H₂O and TeO₂ was used to synthesis CdTe in AAO template.The electrodeposition was conducted potentiostatically at-1.1V versus the reference electrode at room temperature.CdTe nanotube and nanowire were synthesized by controlling the deposition amount of CdTe.The external diameter of CdTe was 100 nm,which are in agreement with the pore diameter of AAO template.The results show that the samples were cubic sphalerite phase of CdTe.The band gap of CdTe nanomaterials was 1.55e V.Mott-Schokkty results showed CdTe was p-type semiconductor.CdTe nanotubes exhibited better performance in photodegradation than CdTe nanowires.CdTe nanoparticle-sensitized TiO₂ nanotube arrays（CdTe/TiO₂ NTAs）were prepared by regular deposition method and dipping and deposition method.The results showed that the CdTe/TiO₂ NTAs prepared by dipping and deposition method exhibited better p-n junction structure and higher photoelectrochemical performances than that prepared by regular deposition method.The XRD results of CdTe/TiO₂ NTAs prepared by dipping and deposition method indicated that CdTe/TiO₂ NTAs were composed of cubic sphalerite phase of CdTe and anatase phase of TiO₂ with good crystallinity.SEM and TEM results showed that CdTe nanoparticles were uniformly deposited into in the tube-to-tube voids of the TiO₂ nanotubes.The UV-vis results showed that the incorporation of CdTe into TiO₂ could improve the absorption of visible light effectively and modify the band gap of TiO₂ to 2.2 eV.The PL results indicated that the photoluminescence intensity of CdTe/TiO₂ NTAs was lower than pure TiO₂ NTAs.The photocatalytic degradation showed the degradation efficiency increased in the order:CdTe/TiO₂﹥TiO₂﹥P25 under the same condition.The reaction kinetics obeyed first-order kinetics.The CdTe/TiO₂ NTAs showed higher photocatalytic activity and better photoelectrochemical performance than other materials.