Visible-light-driven Ta₂O₅ Photocatalysts:Synthesis And Photocatalytic Performance

Ta2O5 as a star material has attracted massive research interests on renewable and clean energy over the past few years. Light-driven water splitting to produce hydrogen and degradation of organic pollutant are the most important applications. However, the process only works under ultraviolet light irradiation due to the wide band gap of Ta2O5(about 4.0 eV). Ultraviolet light accounts for only 3-5% of the sunlight. To utilize sunlight efficiently, Ta2O5 photocatalysts must be responsive to visible light, which is the strongest output range of sunlight. Motivated by developing the photocatalyst that could absorb visible and even infrared light, introduction of dopant into Ta2O5 to narrowing its wide bandgap and incorporation of metal irons into Ta2O5 for forming donor states below the conduction band are the mainstream approaches. In this paper, nitrogen-doped Ta2O5 and hydrogen-doped Ta2O5 samples were prepared by the sol-gel method or hydrogen method. The photocatalytic activity of nitrogen-doped Ta2O5 and hydrogen-doped Ta2O5 samples were obviously improved by photocatalytic test. The main content and viewpoints are as follow:(1) N-doped Ta2O5 is prepared using ethylenediamine as the nitrogen source by the sol-gel method. The heat treatment temperature is systematically examined. UV-vis results indicate the N-doped Ta2O5 catalysts have enhanced absorption in the visible light region, and exhibit high activities on the visible light photocatalytic reactions on the hydrogen production and methylene orange degradation. X-ray diffraction(XRD) and FT-IR results reveal that N has been incorporated into the Ta2O5 lattice. X-ray photoelectron spectroscopy(XPS)results see clearly the N tracks. N-doped Ta2O5 prepared with the sintering temperature of 550 oC performed the highest hydrogen production rate(3.12 mmol.g-1.h-1) and remained 3.1% of methyl orange after 90 min under 350 W xenon lamp irradiation.(2) H-doped Ta2O5 is prepared by hydrogen method. The sintering temperature,time hydride and flow rate, are distribute to the finally samples. This method promotes absorption in the visible light due to the colour of Ta2O5. UV-vis results indicate the H-doped Ta2O5 catalysts have enhanced absorption in the visible light region. X-ray diffraction(XRD) and FT-IR results reveal that H has been incorporated into the Ta2O5 lattice. The sample of H-500 sintering temperature of 500 oC performed the highest hydrogen production and methylene orange degradation by photocatalytic test.