Synthesis, characterization, and photocatalytic activity of tantalum oxide thin films

tantalum oxide;ta2o5;photocatalysis;photocatalyst

Jensen, Cody ; Shannon ; Mark A. ; Cahill ; David G.

关键词: tantalum oxide;    ta2o5;    photocatalysis;    photocatalyst;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/29434/Jensen%2c%20Cody.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

An increasing demand for a low cost alternative for water disinfection and the recent push for green energy has caused an explosion of research in photocatalysis. While TiO2 is considered to be the standard for photocatalysis, there are a number of issues that need to be overcome to push photocatalysis into mainstream applications. In an effort to improve the overall reaction rate, a wider energy gap material, such as Ta2O5, that provides a higher cathodic potential and more flexibility in shifting the energy gap provides a possible alternative. Ta2O5 thin films were synthesized using a sol-gel method and deposited by dip-coating and spin-coating. The thicknesses of the films ranged from 8 nm to 230 nm and were tested to find an optimum thickness based on the quantum efficiency. The photoactivity of the films was measured using a recirculating methylene blue solution. Above 15 nm, the film thickness did not have an effect on the methylene blue degradation rate. To test the premise of being limited by electron-hole transport, the annealing temperature of the films was varied to increase the crystallinity. The films were annealed under a range of temperatures from 450°C to 1200°C. By x ray diffraction measurements, the grain size of the films was found to be relatively stable from 638°C to 1075°C. The films annealed at 1200°C showed the presence of a TaO phase and lacked any indication of a Ta2O5 phase. No correlation between the annealing temperature and photoactivity of the film was found. The photodegradation rate of methylene blue was determined to be limited by surface interactions of the film. A comparison to a TiO2 film synthesized from Degussa P25 powder was used to compare to the Ta2O5 films. The activity was found to be higher for the TiO2 films. However, the amount of catalyst and surface area of the TiO2 were unknown and made conclusive quantitative comparisons challenging.