Preparation Of N-hybridized G-C₃N₄ With Amide Molecule Assistance And Enhancement Of Its Photocatalytic Performance By Ag Particles

Photocatalytic technology is a clean,efficient and green technology,which is widely used in photocatalytic degradation of pollutants.Traditional photocatalysts TiO₂ and ZnO are wide-band gap semiconductor materials,which can only absorb less than 5% of the ultraviolet light in the sunlight,and can not make full use of visible light.In order to utilize sunlight efficiently,it is a priority to develop photocatalysts with high degradation performance under visible light.Graphite phase carbon nitride（g-C₃N₄） is a vision-responsive non-metallic polymer semiconductor photocatalytic material with good chemical and thermal stability.However,the traditional calcined g-C₃N₄ limited its catalytic activity due to its low specific surface area,weak visible light absorption capacity and easy recombination of photogenerated electrons and holes.In this paper,g-C₃N₄ was modified by N-element hybridization and supported noble metal Ag nanoparticles,which solved the problems of small specific surface area and high photoelectron-hole recombination rate,improved the photocatalytic activity of the photocatalyst,and provided a new idea for preparing the g-C₃N₄-based composite photocatalyst with high catalytic performance.The specific research contents are as follows:（1）Ag/N-g-C₃N₄ composite photocatalysts were prepared by using melamine as precursor and adding AgNO₃ with acryloylglycinamide（NAGA）to assist its polymerization,and Ag nanoparticles were loaded on the surface of N hybridized g-C₃N₄（N-g-C₃N₄）with large specific surface area by one-pot method.Compared with the conventional g-C₃N₄,Ag/N-g-C₃N₄increased the specific surface area,expanded the visible light absorption range and had a narrower band gap.In addition,heterojunctions were formed between Ag nanoparticles and g-C₃N₄.At the same time,the mobility of carrier is accelerated by the local surface plasmon resonance（LSPR）effect of Ag nanoparticles,and the recombination of photogenerated electrons and holes is reduced.In the experiments of the composite photocatalytic materials for the degradation of methylene blue and amaranth red,Ag/N-g-C₃N₄-3 showed excellent catalytic performance,and the degradation efficiencies of 67.9%and 99.7%for methylene blue and amaranth red,respectively,were achieved within 30 min.Compared with the conventional g-C₃N₄,the degradation reaction rates of the composite photocatalyst for methylene blue and amaranth red were increased by 2.9 and 14 times,respectively.（2）Sparse porous g-C₃N₄ nanosheets（CGCN）were successfully prepared by introducing cyano at the skeleton edge of g-C₃N₄ by high temperature calcination with urea and NAGA as raw materials,and then the Ag⁺was reduced by Torrance’s test method.Ag/CGCN composite photocatalyst was obtained by loading Ag nanoparticles onto CGCN surface to construct heterogeneous structures.The combined effect of localized surface plasmon resonance（LSPR）effect of Ag nanoparticles and cyanide structural defects resulted in a broader light absorption range while promoting charge separation.The excellent photocatalytic activity was demonstrated in the experiments for the degradation of sulfamethoxazole（SMX）by simulated sunlight irradiation.The experimental results showed that cyano and Ag nanoparticles as electron capture centers jointly promoted charge separation and reduced the complexation rate of electron-hole pairs.Ag/CGCN-4 degradation rate was 42.4 times higher than that of pristine g-C₃N₄,and the degradation efficiency reached 99.9% within 30 min.