The Synthesis Of The Molecular Framework Of Graphitic Carbon Nitride And Its Photocatalytic Degradation Of Organic Pollutants

With the rapid development of industry,the water pollution is increasingly affecting the survival of human beings,animals and plants.The green and efficient technologies of pollutant degradation have been attracting people’s attention and research.In recent years,the photocatalytic degradation of pollutants using semiconductor materials has gradually become a hot spot for researchers,among which the development and design of efficient photocatalysts is the key topic of photocatalysis technology.Graphitic carbon nitride(gC3N4)has gradually become a hotspot catalyst in the field of photocatalysis due to its unique energy band structure,visible light response,stable physicochemical properties,low cost and easy synthesis.However,it also has the disadvantages of small specific surface area,easy recombination of photogenerated electron-hole pairs,slow charge migration rate and low utilization of visible light which limit the photocatalytic activity of g-C3N4.In order to solve partial of these problems,2,4-diamino-6-methyl-1,3,5 triazine,2,4,6-triaminopyrimidine and cyanuric acid were used to synthesize carbon-doped carbon nitride by thermal condensation reaction with dicyandiamide or melamine as feedstock.The broader visible light response and enhanced separation and migration efficiency of carriers enhance its photocatalytic degradation activity.The detail studies of this thesis are as follows.(1)Two materials of carbon-doped carbon nitride(D-CN,T-CN)were prepared by a simple calcination method using 2,4-diamino-6-methyl-1,3,5-triazine(DMT)and 2,4,6triaminopyrimidine(TAP)as dopant prescursors.DMT and TAP molecules were effectively doped into the network of carbon nitride by replacing melamine,which greatly increasing π-electron density.Under the visible light irradiation(λ>420 nm),the degradation activities of D-CN and T-CN were significantly improved,and the rates of degradation of phenol were 3.1 and 5.5 folds of that of pristine carbon nitride,respectively.(2)The homogeneous carbon-doped nitride carbon(MCT-CN)with specific surface area was obtained by using the supramolecular aggregates as precursors formed by melamine,cyanuric acid and TAP,followed by high temperature calcination.The method of supramolecular self-assembly not only facilitated the uniform distribution of doped molecule,but also increased the specific surface area and active sites of carbon doped nitride carbon.In addition MCT-CN showed better electrical conductivity and great πelectron conjugated system from carbon-doping and special structure,which further promoted the separation and transfer of photogenerated carriers.At the same time,MCTCN exhibited more excellent degradation activity of phenol under the visible light irradiation(λ>420 nm),and its degradation rate was about 20.1 folds of that of pristine carbon nitride.It still maintained steady activity after five times of cycling photocatalytic measurements.