Metal Ions Doped Pyrochlore Sodium Tantalate: Preparation And Its Photocatalytic Activities

Photocatalysts have attracted much attention due to their widely applications in dispose of organic pollutants. Up to date, numerous researchers have been encouraged to develop visible-light-driven photocatalysts exhibiting high efficient photocatalytic performance. Basing on previous literatures, it's found that sodium tantalate with pyrochlore structure show higher photocatalytic activity than that of sodium tantalate with perovskite structure. This work reports on the preparation of pure and metal ions doped NaTaO3 nanocrystals with pyrochlore structure via a low temperature hydrothermal method. The samples were carefully characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible diffuse reflectance spectrometry (UV-Vis) and Fourier transform infrared spectroscopy (FTIR).A series of pyrochlore type sodium tantalate nanocrystals were successfully prepared by modulating the different reaction time, temperature and pH value. It's found that the alkali concentration played critical role in the phase transformation from perovskite structure to pyrochlore type sodium tantalate. As the NaOH concentration was in the range of 0.1-3M, a pure phase of pyrochlore type sodium tantalate was obtained. SEM images indicated the particle size of the as-prepared Na2Ta2O6 nanocrystals was about 10 nm. Moreover, EDS data confirmed the formation of pyrochlore type Na2Ta2O6 nanocrystals. The bandgap energy was calculated to be 4.51 eV, which is a bit smaller than that reported previously. Under UV light irradiation, Na2Ta2O6 exhibited high efficient photocatalytic properties for degradation of MB.La3+ and Zn2+ doped Na2Ta2O6 nanocrystals were also prepared under the same procedure. Basing on XRD analysis, it is clearly seen that all diffraction peaks for doped samples shifted to the higher angle, indicating La3+ and Zn2+ substituted at Na+ sites in Na2Ta2O6 host lattice. According to UV-visible spectra, the bandgap energies of doped samples showed a red shift in comparison to pure Na2Ta2O6 nanocrystals. On the other hand, FT-IR results indicated that the characteristic vibrational bands of Ta-O showed a blue shift, which can be explained by charge distribution effects. The photocatalytic activities of doped samples were highly enhanced than that of pure Na2Ta2O6 nanocrystals.