Study On Modification Design Based On G-C₃N₄ And Its Photocatalytic Degradation Of Formaldehyde Gas

Since the beginning of the 21st century,the highly comprehensive development of the society has made the use of chemical products very frequent,and formaldehyde is a contaminant in chemical products which is very harmful to human health.No dangerous by-products are produced in the process of photocatalytic oxidation,and it uses sunlight to stimulate the reaction,which makes the photocatalytic oxidation method become the cleanest and most energy saving method of formaldehyde degradation.g-C₃N₄semiconductor catalyst has become one of the most popular catalysts because of its simple and easy operation of preparation methods and high photocatalytic efficiency.In this paper,through the design of modification of g-C₃N₄,the degradation effect and mechanism of the composite catalyst for formaldehyde pollutants were studied.The specific research contents are as follows:（1）The composite catalyst Ag/g-C₃N₄/Zn O was synthesized by hydrothermal-calcine-reduction using g-C₃N₄as matrix.The combination of large porous Zn O and sheet g-C₃N₄provides more attachment sites for formaldehyde pollutants,and the increase of formaldehyde concentration to a certain extent promotes the efficiency of photocatalytic degradation of formaldehyde.The efficiency of formaldehyde degradation over g-C₃N₄/Zn O and Ag/g-C₃N₄/Zn O catalysts reached74.1%and 81.2%,respectively.The photocatalytic activity of Ag/g-C₃N₄/Zn O catalyst is 1.3 times and 2.6 times higher than that of Zn O and g-C₃N₄catalyst.The improvement of catalyst activity is mainly due to the synergistic effect of heterojunction and metal silver plasma.h⁺,O₂^-and·OH are the main active groups of photocatalysis.The cyclic experiments show that the Ag/g-C₃N₄/Zn O ternary composite catalyst has good sustainable performance.（2）Ag/g-C₃N₄/Ti O₂composite catalyst was prepared by simple calcination-reduction method using g-C₃N₄as matrix.The degradation efficiency of Ag/g-C₃N₄/Ti O₂catalyst for formaldehyde reached 84.71%,which was 2.65 times and1.22 times higher than that of monomer g-C₃N₄and Ti O₂.The formation of the heterojunction between g-C₃N₄and Ti O₂can effectively play the role of g-C₃N₄photosensitizer,and the doped silver nanoparticles can not only act as a trap for photogenerated electrons but also play the role of reducing the Schottky barrier of the catalyst.Through the analysis of ion chromatography,we found that the intermediate product in the process of formaldehyde oxidation is formic acid,and the mechanism of photocatalytic degradation of formaldehyde was analyzed according to the energy band structure of the catalyst.In this paper,g-C₃N₄as substrate composite catalysts were synthesized.The mechanism of formaldehyde degradation was studied by describing the characterization and mechanism of the catalyst in detail.In terms of preparation materials,preparation methods and photocatalytic effect,the catalysts prepared have certain practical reference and application significance.