A₂Nb₄O₁₁?A=Na?K? And Its Composite Catalyst Photocatalytic Performance Study

In recent years, with the incessant development of society, the increasing shortage of fossil energy and problem of the pollution caused by the production and life become increasingly serious, the energy crisis and environmental pollution become an urgent problem. Because the photocatalytic technology not only can make use of solar water splitting to product hydrogen and degradation of pollutants, but also has low cost, simple operation, mild reaction conditions, no secondary pollution and so on, it becomes one of effective ways to solve the current energy crisis and environmental pollution.But traditional photocatalysts such as the most common used TiO₂ photocatalytic materials due to the narrow bandgap, low solar energy utilization, low quantization efficiency, hindered the wide application of photocatalytic materials. Niobate because of its unique electronic structure and the energy band structure, excellent photocatalytic performance, become a photocatalytic technology hotspot in recent years. This paper studies the tungsten bronze type niobate compounds A₂Nb₄O₁₁?A = Na, K? synthesis and photocatalytic performance, on this basis, in order to further improve niobate A₂Nb₄O₁₁ photocatalytic efficiency, but also studies the A₂Nb₄O₁₁/C₃N₄ composite catalyst catalytic properties.This paper first use of Nb₂O₅ and Na₂CO₃ as raw materials to synthesis Na₂Nb₄O₁₁ by solid state method. Then Na₂Nb₄O₁₁ mixed with urea in different quality ratio roast, prepare a series of Na₂Nb₄O₁₁/C₃N₄ composite catalyst.The samples were characterized By X-ray powder diffraction?XRD?, scanning electron microscope?SEM?, ultraviolet visible diffuse reflection spectroscopy?UV vis?, Fourier infrared spectrum?FTIR? and fluorescence spectroscopy?PL?, etc. Research data show that: Na₂CO₃ and Nb₂O₅ mole ratio of 1:2 mixed equably, under air atmosphere in a tube furnace 850 ?roasting 12 h can acquire high purity Na₂Nb₄O₁₁, only C₃N₄ and Na₂Nb₄O₁₁ no other impurities after Na₂Nb₄O₁₁ mixed with urea roasting.by degrading 2.5 mg/L rhodamine B in the full spectrum or visible light solution research the photocatalytic performance of the composite catalyst, the experimental results show: the composite catalyst Na₂Nb₄O₁₁/C₃N₄ photocatalytic performance is obviously better than single Na₂Nb₄O₁₁ photocatalytic property, characterization of samples show that the composite catalyst's absorption threshold redshift, spectral response range broaden, at the same time electronic- hole recombination rate decreases, resulting in the improvement of the photocatalytic properties of the composite catalyst;And when Na₂Nb₄O₁₁ with urea quality ratio is 1:5 the photocatalytic performance of composite catalyst is best.Based on the above,in order to obtain better catalytic efficiency tungsten bronze type niobate compound, the paper change A element of the compound A₂Nb₄O₁₁ see if the A element has an effect on the structure and photocatalytic properties of A₂Nb₄O₁₁ and its composite catalyst. This article change A element of the compound A₂Nb₄O₁₁ into its congener K element, analysis photocatalytic properties of K₂Nb₄O₁₁ and its composite catalyst through the same method, the paper use of Nb₂O₅ and K₂CO₃ as raw materials to synthesis K₂Nb₄O₁₁ by solid state method?Then K₂Nb₄O₁₁ mixed with urea in different quality ratio roast, prepare a series of K₂Nb₄O₁₁/C₃N₄ composite catalyst., and then the samples were characterized, analyzed the data, and compared with the experimental data of Na₂Nb₄O₁₁ at the same time. Research data show that K₂CO₃ mixed with Nb₂O₅ molar ratio of 1:2, while K₂CO₃ excess about 5%, under air atmosphere in a tube furnace 950 ?roasting 24 h can acquire high purity K₂Nb₄O₁₁, only C₃N₄ and K₂Nb₄O₁₁ no other impurities after K₂Nb₄O₁₁ mixed with urea roasting.Compared with the synthesis Conditions of K₂Nb₄O₁₁ and Na₂Nb₄O₁₁, not only K₂Nb₄O₁₁'s roasting temperature and roasting time increase, but also K₂CO₃ excess 5%, this may be related to the K's boiling point lower than Na, and K is volatile. then, by degrading 2.5 mg/L rhodamine B in the ultraviolet or visible light solution research the photocatalytic performance of K₂Nb₄O₁₁ and its composite catalyst, the experimental results show : the bandgap of K₂Nb₄O₁₁ is lessen than Na₂Nb₄O₁₁, K₂Nb₄O₁₁ show the stronger catalytic performance; the composite catalyst K₂Nb₄O₁₁/C₃N₄ photocatalytic performance is superior to single K₂Nb₄O₁₁ photocatalytic performance, after K₂Nb₄O₁₁ and C₃N₄ composite, the spectral response range broaden, while the electron- hole recombination rate decreases, so that the photocatalytic properties of the composite catalyst is obviously improved, which is similar to composite catalyst Na₂Nb₄O₁₁/C₃N₄ performance,However when K₂Nb₄O₁₁ with urea quality ratio is 1:10 the photocatalytic performance of compared composite catalyst is best.