Synthesis And Investigation Of TiO₂Nanotube Arrays Films And Their Photocatalytic Activity

With the development of the society, environmental pollution become one of thehot spots, people pay widespread attention to environmental protection field. In recentyears, scientists focus on the semiconductor catalytic material to solve this problem,which is non-toxic, rich resources, stabilization and high activity. However, theapplication of traditional nano-TiO₂powder is limited due to its agglomeration in theuse and difficult recovery after the use, besides secondary pollution caused to theenvironment is another shortcoming. In this paper, to solve the shortcomings of thetraditional nanomaterials, we fabricated the TiO₂nanotube arrays film on titanium byanodic oxidation, and Ce³⁺, Gd³⁺were effective doped TiO₂nanotubes by theimpregnation method. the experimental results are as follows:1.The one-dimensional structure of TiO₂nanotube arrays film was prepared byanodic oxidation on titanium foil. Field emission scanning electron（FESEM） and theX-ray diffraction（XRD） characterized the morphologies and crystal structures of TiO₂nanotubes, respectively. The influences of process parameters including oxidationvoltage, water temperature, the concentration of F-and annealing temperature on themorphology and crystal structure of TiO₂nanotubes were investigate, the factorsand mechanism of TiO₂nanotube growth were also theoretically described. As aresult, the oxidation voltage, water temperature, the concentration of F-affect theformation of the nanotube diameter and the tubewall. Annealing temperature affectthe crystalline phase and morphology of TiO₂nanotubes, with the annealingtemperature increasing, anatase phase appeared first, then rutile phase exhibitted athigher temperatures, and the content of rutile phase increased continuously whileanatase content decreased, TiO₂nanotubes were rutile phase mainly at800℃. Thetubular structure collapsed at680℃. 2. The photocatalytic activity of TiO₂nanotubes prepared under various processparameters and different initial concentrations and initial pH of methyl orange bydegradation of methyl orange.30V oxidation voltage,30℃waterbath temperatureand0.5wt%NH4F electrolyte are the optimal parameters, under which the nanotubediameter is about80-100nm, the length is approximately4.89μm. According to thedegradation of methyl orange, the optimum values of annealing temperature, initialconcentration and initial pH were550℃,10mg/L and3, respectively. The bestdegradation rate of methyl orange was76.4%under ultraviolet light for4h.3.Rare-earth ions Ce³⁺and Gd³⁺-doped TiO₂nanotubes were prepared byimpregnation method. According to the photodegradation of methyl orange, theoptimum solutions of Ce（NO3）3and Gd（NO3）3were both0.01mol/L. Compared to thepure TiO₂nanotubes film, the photodegradation efficiency of methyl orangephotodegraded by rare-earth ions doped TiO₂nanotubes was increased by18.2%and16.2%, respectively. Obviously, Ce³⁺doped TiO₂nanotubes have higherphotocatalytic activity than Gd³⁺doped TiO₂nanotubes. The TiO₂nanotubes with theoptimal amount of Ce³⁺or Gd³⁺were analyzed by XRD, SEM and EDS, EDSspectrum exhibits that Ce³⁺and Gd³⁺were successfully doped into TiO₂by theimpregnation method, Ce atoms and Gd atoms relative to the Ti atoms content were1.22%and0.47%, respectively. As a result, XRD patterns didn’t detect the diffractionpeaks of the rare earth oxides which were less content. FESEM shows that therare-earth ions doping does not affect the morphologyies of TiO₂nanotubes. Thediameter of the nanotubes was80-100nm approximately.