Morphological Control Of Tantalum Based Nanomaterials And Their Photocatalytic Properties For Hydrogen Evolution

Tantalum-based photocatalyst materials have a higher conduction band position, which indicates that the photogenerated electrons possess the strong ability of H2 evolution. Therefore, they have expansive prospects in the field of photocatalytic water splitting into hydrogen. In this paper,(NH4)2Ta2O3F6 nanotubes, Ta2O5 nanosheets, Na2Ta2O6 and Na Ta O3 nanoparticles photocatalysts were successfully prepared by hydrothermal synthesis method and calcination method. Meanwhile, the influences of loading Pt on photocatalytic hydrogen generation activities of(NH4)2Ta2O3F6 nanotubes and Ta2O5 nanosheets were also investigated. The morphologies, sizes, compositions of elements, crystalline structures and spectral response areas of the prepared catalysts were characterized by SEM, TEM, EDS, XRD, BET, XPS and UV-Vis DRS analyses. Photocatalytic hydrogen production activities of prepared photocatalysts were studied and discussed.First, the different morphologies of tantalum-based nanomaterials were prepared by hydrothermal method in different conditions. Analysis result indicates that the(NH4)2Ta2O3F6 nanotubes prepared with 0.2 m L hydrofluoric acid are long and uniform at 180 °C for 24 h. Synthesized orthorhombic(NH4)2Ta2O3F6 nanotubes is single crystal semiconductor materials with exposed {202} crystal faces. DRS exhibits that(NH4)2Ta2O3F6 nanotubes possess stronger absorption in the UV region, the band gap of the sample is 3.67 e V. The(NH4)2Ta2O3F6 nanotubes as photocatalysts exhibite a stable and higher photocatalytic activity throgh the hydrogen production test of 9 h circulatory stability. Pt/(NH4)2Ta2O3F6 nanotubes were prepared by photocatalytic reduction method for improving the photocatalytic activity for hydrogen production. The experiment results show that 0.6 wt % Pt has been regarded as an optimal amount of Pt loading to achieve the highest rate of hydrogen evolution, which was about 1.46 times as much as that of the unmodified(NH4)2Ta2O3F6 nanotubes.Secondly,(NH4)2Ta2O3F6 nanotubes were calcinated under different calcination temperatures. The nanosheets with uniform thickness, clear edges and corners were successfully prepared by calcination at 300 °C for 2 h using(NH4)2Ta2O3F6 nanotubes as the precursors. XRD analysis result exhibites that Ta2O5 nanosheets with orthorhombic structure were excellently crystallized. The photocatalytic hydrogen generation activity and stability of Ta2O5 nanosheets and commercial Ta2O5 were carried out. The experimental datas display that hydrogen production rate of obtained Ta2O5 nanosheets is about 3 times as much as that of commercial Ta2O5. Additionally, both of them have good stability of hydrogen production. In addition, the photocatalytic H2 evolution activities of Pt/Ta2O5 nanosheets were also discussed in other systems under visible light.Finally, Na2Ta2O6 and Na Ta O3 nanoparticles were successfully prepared by hydrothermal method in different concentrations of Na OH. The SEM images display that the prepared samples were all small particles. The XRD results show that the samples are transformed from Na2Ta2O6 to Na Ta O3 when the concentrations of Na OH range from 0.5 mol/L to 1.0 mol/L. Moreover, the photocatalytic activities of the prepared catalysts for water splitting were also investigated. Test results indicate that the photocatalytic hydrogen production activity of cubic Na2Ta2O6 is much smaller than the activity of orthorhombic Na Ta O3. Moreover, when the concentration of Na OH is 2.0 mol/L, the obtained Na Ta O3 shows the highest activity with a hydrogen production rate of 1124.72 umol/g.