Preparation And Photoelectric Catalytic Properties Of CuO And Non-metallic Element Modified Carbon Nitride Materials

As a low-cost material,graphite-phase carbon nitride（g-C₃N₄）has excellent physical and chemical properties and can be synthesized with some simple and environment-friendly methods.However,due to the rapid recombination rate of photo-generated electron-hole,high exciton binding energy and wide band gap width,the photoelectrocatalytic activity of the pure g-C₃N₄ is limited,but photoelectrochemical catalytic performance of g-C₃N₄ material can be promote by modifying it.In this work,several modified carbon nitride nano-materials were prepared by semiconductor composite and doping modification,then the properties of photocatalytic and electrochemical activities were studied.The specific work is summarized as follows:（1）Carbon doped porous flake carbon nitride（CCN）was prepared by thermal condensation method using benzotriazole（BTA）as carbon source and melamine as precursor.The effect of doping amount of BTA on its properties and morphology was systematically studied.then the morphology,structure and photocatalytic properties of carbon doped carbon nitride were characterized.The results of X-ray photoelectron spectroscopy（XPS）show that the atomic ratio C/N is 0.89,which is obviously higher than the theoretical value of g-C₃N₄（3:4）,which proves the successful incorporation of C atoms.The specific surface area of CCN is 129 m²/g and the photocurrent is 7 times of that of g-C₃N₄,which indicates that C atom enhances the separation efficiency of photogenerated electron hole.When it was applied to photocatalytic hydrogen production and photodegradation of organic pollutants,the photocatalytic hydrogen production rate of CCN_0.5 nanomaterials is 2348μmol·g^-1·h^-1,which is 13.7 times higher than that of g-C₃N₄,the degradation rate of Rh B(0.1414 min^-1)was 44 times higher than that of g-C₃N₄(0.0032 min^-1).Therefore,carbon doped carbon nitride-CCN can be used as an efficient photocatalyst.（2）S-g-CN nano-materials were prepared by a simple one-step thermal condensation method,and the synthetic parameters such as sulfur source,heating time and heating rate were optimized.The results showed that ammonium sulfate was used as sulfur source,the S-g-CN nanomaterials with 10°C/min heating rate of 500°C for 4 h have the best photohydrogen evolution properties,the photocatalytic rate of hydrogen production is 4923μmol·h^-1·g^-1,which is 28 times higher than that of pure g-C₃N₄.And then the structure and photoelectric properties were characterized.It is found that its specific surface area is up to216.23 m²/g which is 13.1 times higher of pure g-C₃N₄,the thickness of the S-g-CN lamellar is 2.5 nm.Photocurrent response of S-g-CN is 7.8 times that of pure g-C₃N₄.Finally,we advance the photocatalytic electrocatalysis mechanism of S-g-CN nano-materials.（3）Copper complex was synthesized via hydrothermal method with linear small molecules which is hydrolyzed from natural silk material under alkaline conditions as soft template,and copper chloride and Na OH as precursors.CuO/g-C₃N₄ nanocomposites were prepared by polymerization using the mixture of melamine and copper complex.The effects of template,temperature,hydrothermal time and the ratio of CuO to g-C₃N₄ on the morphology of CuO/g-C₃N₄ composite was investigated.The results show that the tubular shape of the 2%CuO/g-C₃N₄ composite material prepared by using the silk as a template and hydrothermal under a temperature of 180°C for 24 h is the most complete and the photocatalysis activity was the highest.The visible light absorption efficiency and photocurrent intensity of CuO/g-C₃N₄ nanocomposites were obviously enhanced and fluorescence intensity was significantly decreased,the photocurrent response value was0.103 m A/cm²,was 2.8 times of pure g-C₃N₄.When the 2%CuO/g-C₃N₄ nanocomposite was used as a catalyst for photo-degradation of Rh B（10 ppm）,the degradation was about100%after 25 min.Moreover,the degradation rate was about 98 and 3.4-folds of pure bulk g-C₃N₄ and CuO.The degradation of Rh B in 25 min can still reach 95%after 5 cycles,suggested the composite material has good stability.its main active species were known from the active species capture test which are·OH and holes,finally,the mechanism of enhanced photocatalytic activity of CuO/g-C₃N₄ was proposed.