Study On The Preparation Of H₃PW₁₂O₄₀/TiO₂-C₃N₄ Composites And Its Photocatalytic Properties

In recent years, Ti O2 photocatalytic material has been widespread concern because of its little pollution, low cost, strong oxidizing characteristics and its chemical stability. But Ti O2 only can absorb ultraviolet light, it has low utilization of sunlight; And the electron-hole pairs of Ti O2 excited by light is easily compound; The application of g-C3N4 is increasingly widespread. This article is committed to preparing a composite catalyst with excellent catalytic performance, low pollution,and better reusability.By the method of sol-gel combined with programmed temperature H3PW12O40 was prepared first, made the H3PW12O40 and anatase Ti O2 mixed together. Then use the method of thermal condensation urea to prepare the g-C3N4. Then by the steps of ultrasound we get the H3PW12O40/Ti O2-g-C3N4 ternary catalyst material.We characterized the crystalline structure, constituent elements, light absorption properties and the morphology of the catalyst material by using modern materials testing methods include X-ray powder diffraction, X-ray photoelectron spectroscopy,infrared spectroscopy, UV-visible diffuse reflectance absorption spectrum, fluorescence spectroscopy and transmission electron microscopy.The results show that Ti O2 in H3PW12O40/Ti O2-g-C3N4 composites still have anatase crystal form, g-C3N4 has not changed its original structure, g-C3N4 also has not changed its original structure. H3PW12O40 material is evenly distributed among Ti O2,H3PW12O40 bound in the composite meteral Chemically. XPS detects H3PW12O40 / Ti O2-g-C3N4 catalyst contained C, N, O, Ti, W these five elements in the sample. The band gap of g-C3N4 is 2.70 e V, and the bandgap energy of H3PW12O40/Ti O2-g-C3N4 is 2.88 e V. So after load of H3PW12O40/Ti O2 catalyst material, the gap energy of catalyst material has increased, thereby increasing its catalytic properties.Fluorescence spectroscopy showed fluorescence intensity of the ternary complex catalysts heterojunction than the g-C3N4 significantly decreased, indicating that there was a clear fluorescence quenching phenomenon in H3PW12O40/Ti O2-g-C3N4 Heterojunction, reducing the rate of photogenerated electrons and holes recombination.We have did the effect of different loading experiments, the results showed that when the mass ratio of g-C3N4 and H3PW12O40/Ti O2 is 2:8, catalytic effect of the ternary complex catalysts is the best. The article also by comparing Ti O2, g-C3N4, H3PW12O40/Ti O2, Ti O2/g-C3N4, H3PW12O40/Ti O2-g-C3N4 these five photocatalytic materials under simulated solar light and visible light degradation efficiency of Rhodamine B solution of 20 ppm respectively,The results show that photocatalytic degradation efficiency of H3PW12O40/Ti O2-g-C3N4 under simulated sunlight conditions of Rhodamine B is always better than several other catalyst in this paper. When the simulated sunlight irradiation time is 20 min, catalytic efficiency of Ti O2 、 g-C3N4 、 H3PW12O40/Ti O2 、 Ti O2/g-C3N4 、H3PW12O40/Ti O2-g-C3N4 are 5.6%、42.6%、13.3%、36.5%、89.4% and 98.3% respectively. In visible light photocatalytic activity of the ternary complex is also the best, after the visible light illumination 60 min, catalytic efficiency of Ti O2、g-C3N4、H3PW12O40/Ti O2、Ti O2/g-C3N4 and H3PW12O40/Ti O2-g-C3N4 are 8.4 %, 73.5%, 45.3%, 78.3% and 90.4%.By the test of recycling ternary catalyst under simulated sunlight,the degradation efficiency of three reused in 30 min were 99.8%, 93.7% and 88.7%,proved H3PW12O40/Ti O2-g-C3N4 have good reuse performance.