Analysis On The Construction Of Controllable Phase Of Tungsten Oxide Compositing G-C₃N₄ And Their Photocatalytic Performance

With the situation of the modern scientific and technological progress,rapid economic and social development,environmental pollution has attracted more and more attention,environmental pollution has become more and more serious.Reducing environmental pollution and building a green China has always been the primary issue for scientific researchers.Since 1972,researchers have found that TiO₂ has visible light absorption and has been used as photocatalytic degradation of pollutants.However,there are still many problems in the application of TiO₂ as a semiconductor in the field of photocatalysis,such as wide band gap,low utilization rate of solar energy and high photogenerated electron hole recombination rate,which greatly limit its practical application.So scientists began to search for the semiconductor photocatalysts which have the better photocatalytic activity than TiO₂.g-C₃N₄as a non-metallic semiconductor photocatalyst favored by scientists in this century has many advantages:wide visible light absorption,adjustable interband energy levels,high chemical stability,abundant edge N source,non-toxic and harmless.As an environmentally friendly carbon material,g-C₃N₄ is often used degrade organic pollutants and degrade aquatic hydrogen.Under visible-light photocatalysis,photogenerated electron holes and oxygen generate superoxide radicals and hydroxyl radicals,which can degrade organic pollutants quickly without secondary pollution.It is well known that single-component photocatalysts have many shortcomings for example the rapid combination of photogenerated electrons and holes.While the synthesis of heterojunction composites with suitable band structure by two kinds of semiconductors can improve the separation of charge carriers and the photocatalytic activity and stability of photocatalysts.In this paper,the 2D carbon material g-C₃N₄ was chosen as the main research object,and WO₃ with different phase were synthesized by changing chemical reaction conditions.It could improve the photocatalytic degradation efficiency of g-C₃N₄ to Rhodamine B under visible light by using the method of solid phase roasting synthesis.The main research results of this paper include:?1?Bulk g-C₃N₄ and h/m-WO₃ were synthesized by pyrolysis of urea and ammonium tungstate at high temperature.Photocatalytic results showed that the catalytic effect of h/m-WO₃/g-C₃N₄ was significantly improved.When the mass ratio of g-C₃N₄ to h/m-WO₃ was 3.0,the degradation rate of 40 mg/L rhodamine B solution could reach 99%within 150 minutes under the irradiation of tungsten iodide lamp.?2?Two different forms of WO₃:h-WO₃ and m-WO₃ were synthesized by changing the calcination temperature and time of precursor Ammonium Tungstate by the same synthesis method and the optimum mass ratio of reactants.Three different forms of WO₃:h-WO₃,h/m-WO₃ and m-WO₃ then with g-C₃N₄ were synthesized to be the heterojunction photocatalysts.Combining with scanning electron microscopy?SEM?,the uncertainty of the influence of different supporting forms of WO₃ and g-C₃N₄ on photocatalytic reaction was eliminated under the same reaction conditions.The results showed that the photocatalytic degradation ability of g-C₃N₄ was greatly improved after loading hexagonal phase of WO₃ under visible light to degradate the organic pollution RhB.According to the SPV characterization of three composite photocatalysts,it can be found that H1G3?h-WO₃ and g-C₃N₄ have a mass ratio of 1:3?has the strongest SPV signal,indicating that the separation and transmission efficiency of photogenerated electron-hole pairs at the interface of H1G3 heterostructure structure is the highest and the photocatalytic activity is the highest.The results are consistent with photocatalytic degradation experiments.?3?Oxygen defect can enlarge the wavelength absorption range of the photocatalyst,promote the separation of the photogenic hole electron pair,and can also be used as electron capture center.In this paper,under the condition of calcined at 400oC in a tubular furnace among the reducing atmosphere,N₂,h/m-WO₃-oxygen vacancy?h/m-WO₃-OV?was synthesized.Then,the heterojunction of h/m-WO₃-OV/g-C₃N₄ was synthesized by the same method.Through the Raman characterization of h/m-WO₃-OV,we found that the longer the heterogeneous junction was roasted under N₂,the lattice matching of h/m-WO₃ increased and then decreased,the half peak width and the photocatalytic performance increased and then decreased,too.Among them,h/m-WO₃-60 min-OV crystal lattice has the largest crystal lattice,the widest half-peak width and the largest photocatalytic performance.The SPV characterization results show that h/m-WO₃-60min-OV photogenerated electron-hole pair has the highest separation efficiency,indicating that more photogenerated carriers participate in the photocatalytic reaction,thus he photocatalyst degradation efficiency was greatly improved.The RhB degradation experiment of the target pollutant showed that the photodegradation effect of h/m-WO₃-60min-OV/g-C₃N₄ complex was the best.