Study On The Preparation And Photocatalytic Property Of Composites Based On G-C₃N₄

Photocatalytic technology is a feasible solution to the energy and environmental problems.In a wide variety of photocatalytic materials,graphite-phase carbon nitride materials(g-C3N4)are widely used as photocatalytic materials due to its controllable electronic structure,good chemical stability and thermal stability,nontoxic and harmless,and rich,low and cheap raw materials needed for the synthesis process.Continuous progress has been made on g-C3N4 in photocatalytic decomposition of water to hydrogen and photocatalytic degradation of organic pollutants.Carbon nitride synthesized by direct thermal polymerization is generally block,smaller than surface area,low utilization rate of visible light and easy to compound photocarriers.Material composite and energy belt engineering are effective ways to optimize the performance of photocatalyst.This paper intends to improve the photocatalytic performance of g-C3N4 by means of dye sensitization and the construction of ternary composites.The morphology,structure,size and properties of the materials were analyzed and characterized by various testing methods.The photocatalytic activity of the material was studied by photocatalytic decomposition of water for hydrogen production and degradation of organic pollutants.The main research contents are as follows:(1)Preparation and photocatalytic performance of dye-sensitized g-C3N4 composites:two-dimensional g-C3N4 nanosheets were prepared by hydrochloric acid etching method,and the one-dimensional 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin(TPPH)nanowires were synthesized by acid-base neutralization and selfassembly.Then,the TPPH/g-C3N4 nanosheets with different mass percentage of TPPH were prepared by surfactant assisted co-assembly method.The prepared materials were analyzed and characterized by field emission scanning electron microscopy(SEM),field emission transmission electron microscopy(TEM),polycrystalline X-ray diffraction(XRD),molecular fluorescence spectroscopy(PL),Fourier transform infrared spectroscopy(FTIR),atomic force microscopy(AFM)and UV-Visible diffuse reflectance spectroscopy(UV-Vis),among others.Photocatalytic hydrogen evolution performance of the composite samples under full spectrum irradiation was explored,and the photocatalytic degradation performance of the samples under simulated visible light irradiation was investigated with methyl orange(MO)as the target degradation material.It can be seen from the results that the hydrogen production of 1.67%TPPH/g-C3N4 without any co-catalyst under full spectral irradiation reached 10.87 mmol·g-1·h-1,2.68 times higher than that of monocomponent g-C3N4.The improvement of the performance is mainly due to the enhancement of the light absorption capacity of the composite samples after the introduction of TPPH,and the red shift of the absorption band edge reaches the near infrared range.At the same time,from the experimental results of photocatalytic degradation of MO,it can be seen that the degradation effect of 1.67%TPPH/g-C3N4 is the best,reaching 96.29%,which is 2.41 times higher than that of single g-C3N4.(2)Design and photocatalytic properties of ternary composites based on energy band engineering:?-Fe2O3 was synthesized by hydrothermal method,and then ?Fe2O3/g-C3N4 was prepared by calcination of melamine and ?-Fe2O3.TPPH/?Fe2O3/g-C3N4 ternary composites were finally prepared by adding porphyrin TPPH solution.The prepared materials were characterized by SEM,XRD,FTIR,PL and UV-Vis et al.The influence factors of photocatalytic degradation of organic dyes Rhodamine B(RhB)and methyl orange under visible light irradiation were investigated.The degradation rate of 0.75%TPPH/?-Fe2O3/g-C3N4 reached 93.22%,which was 2.04 times higher than that of monocomponent g-C3N4.In the MO degradation experiment,0.75%TPPH/?-Fe2O3/g-C3N4 degradation rate is the highest,reaching 81.28%,which was 2.39 times higher than that of single g-C3N4.The cyclic experiments of RhB and MO degradation show that TPPH/?-Fe2O3/g-C3N4 ternary composites not only have good photocatalytic degradation ability,but also have good photochemical stability.