Research On Modification Of Graphite-like Carbon Nitride For Photocatalytic Degradation Of Organic Pollutants

Photocatalytic technology can be used to decompose water for producing hydrogen and degrade organic pollutants,as the new green technology to solve energy crisis and environmental pollution problems.Graphite carbon nitride?g-C₃N₄?is a kind of non-metallic carbon-nitrogen polymer,with the unique advantages such as suitable band gap,good chemical and thermal stability,simple preparation methods and so on.However,the poor absorption ability of carbon nitride to visible light and the high efficiency of photogenerated electrons and holes recombination seriously limit its practical application.Therefore,in this paper,the modification of g-C₃N₄ by size control,construction of heterojunction and supported cocatalyst was carried out in the simple and quick ways,which significantly improves the performance of photocatalytic degradation of organic pollutants,and it has important practical significance.The main research contents and results of this paper are as follows:G-C₃N₄ was prepared by thermal condensation with melamine as the precursor,then which was stripped by calcining and ultrasound.Optimizing the calcination times and ultrasonic time to obtain the best experimental conditions,and the possible mechanism of degradation of Rh B by g-C₃N₄ nanosheet under visible light was explored.The results showed that the method of secondary calcination combined with ultrasonic treatment effectively improves the activity of degradation of Rh B by g-C₃N₄ material.Pristine g-C₃N₄ was obtained by calcining dicyandiamide,and Ag₂WO₄ was successfully coated on g-C₃N₄ sheet surface by in situ precipitation method.Ag₂WO₄/g-C₃N₄heterojunction photocatalyst was obtained without changing the morphology and crystal structure of g-C₃N₄,and Ag₂WO₄ coating quality was regulated to achieve the optimal composite ratio.The coating of a small amount of Ag₂WO₄ improves the electron transfer efficiency of g-C₃N₄ and effectively inhibits the recombination of photogenic carriers,thus significantly improving the performance of Ag₂WO₄/g-C₃N₄.The carbon quantum dots?CQDs?/g-C₃N₄ composite photocatalyst was synthesized by thermal condensation polymerization of thiourea added proper amount of carbon quantum dot solution.Regulating the volume of the carbon quantum dot solution,the optimal ratio of CQDs:g-C₃N₄ composites was obtained,and CQDs enhances the light absorption ability of g-C₃N₄,and which be used as an electronic storage to improve the carrier separation efficiency.The degradation efficiency of the composite to TC is 1.5 times that of the pristine g-C₃N₄.