Photocurrent enhancement of heat treated CdSe- sensitized titania nanotube photoelectrode

摘要

The self-organized titania nanotube arrays (NTAs) fabricated by anodisation has gained enormous interest due to its high spatial orientation, excellent charge transfer structure, and large internal surface area; all are crucial properties influencing the absorption and propagation of light. In this study, a composite material, CdSe nanoparticle/ TiO_2 nanotube arrays (CdSe/TiO_2 NTAs) were assembled through the insertion of CdSe nanoparticles onto the anodized TiO_2 nanotube arrays via electrochemical deposition. The annealing temperature of CdSe/TiO_2 NTAs was varied from 200 to 350 ℃ and was found to play an important role in controlling the formation of CdSe nanoparticles on TiO_2 NTAs. Characterizations of the films were performed by using field emission scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, high resolution transmission electron microscopes, X-ray diffractometry and UV-visible diffuse reflectance spectroscopy. The transient photocurrent was examined in a three-electrode system under halogen illumination by using the prepared film as the photoanode. It was found that the CdSe nanoparticles were susceptible to spread through electrochemical deposition and formed on the nanotubes by annealing in nitrogen atmosphere. The increment in annealing temperature has resulted in greater amount of CdSe loaded onto TiO_2 nanotube arrays. Therefore, a suitable annealing temperature can enhance the particle interaction, leading to considerable improvement in PEC performance. The sensitized CdSe/TiO_2 NTAs annealed at 250 ℃ displayed 84 folds improvement in photoconversion efficiency than that of bare TiO_2 NTAs counterparts.