Preparation And Photoelectric Properties Investigation Of Nanostructured TiO₂Photocatalysts

As classic photocatalytic materials, TiO2have always attracted a lot of attention from researchers. The research on their photoelectric performance has never been stopped, and the discoveries of the relationship between structure and performance were extremely meaningful. Due to the unique one-dimensional structure of TiO2nanotube arrays (TNTAs), TiO2could act as good carrier collector and transporter reducing the recommendation of photogenerated carrier. Thus, we could develop more excellent photocatalysts based on TNTAs.In this paper, TNTAs were prepared by anodization. The effects of annealing temperatures on morphology, crystal structure, crystalline size and phase composition were studied, and the relationship between phase and photoelectric properties was discussed. It was found that when annealed at500℃, TNTAs containing mixed antase and rutile was obtained. The mass fractions of anatase and rutile were41.2%and58.8%, respectively. The existence of anatase/rutile layered phase junction was determined by the analysis of XRD spectrum, Raman spectrum, and UV-Vis absorption spectra. The structure of the phase junction was that anatase lied on the top of TNTAs and rutile at the bottom. Due to the existence of phase junction, an optimal performance was achieved in the photoelectric measurements of the500℃-annealed sample. The value of photocurrent of the sample with phase junction was120μA/cm2, which was1.5times as much as that of the sample with pure anatase. For electrochemical impedance spectroscopy, it was suggested that the phase junction could promote the photo induced electrons transfer from anatase to rutile, thereby improved photoelectric properties were investigated.Nanotube-based composite structure TiO2was facilely prepared by a two-step method: highly ordered TiO2nanotube arrays were first fabricated through the anodization process and then followed by mechanical milling. After analyzing BET data, photocurrent measurements, photolurminescence spectra and electrochemical impedance spectroscopy of the composite structure TiO2, it was proved that the best milling time was5h. The specific surface area of5h-milled sample was42.14m2/g,51.2%increase was obtained comparing to TNTAs. Under the irradiation of100mW/cm2UV light, the photocurrent density of hierarchical structured TiO2was120μA/cm2, which was3times higher than P25. Comparison of photocatalytic (PC) and photoelectrocatalytic (PEC) degradation efficiencies, it was showed that the hierarchical structured TiO2nanotubes were more suitable for PEC applications.16%PEC degradation efficiency was achieved in the Methyl Orange degradation experiment by composite structure TiO2comparing to P25.