Preparation And Photocatalytic Properties Of Silver/graphite Phase Carbon Nitride (Ag/gC 3 N 4 )

The problems of energy shortage and environmental pollution have been becoming increasingly serious and affected human life gradually.Photocatalytic technology shows great potential since it can utilize solar energy to produce hydrogen and degrade environmental pollutants.In contrast to the traditional UV light responding photocatalyst,a new kind of visible-light-driven photocatalyst g-C₃N₄ has attracted much attention for its unique electronic structure and stable physical and chemical properties and a lot of work have been carried out to study the g-C₃N₄.However,the pure g-C₃N₄ still exists some weaknesses such as small specific surface area and low utilization of visible light and high recombination rate of photogenerated charge carriers,which restricts its application.Therefore,it is of great practical significance to study how to improve the photocatalytic activity of g-C₃N₄ under visible light.Herein,we provide a pathway to increase the specific surface area of g-C₃N₄ and to dope noble metal Ag particles on the g-C₃N₄ substrate.Firstly,the g-C₃N₄ nanosheets with mesoporous structure were obtained via the template free method by taking full advantage of a large number of gas produced by NH₄ Cl during heating with C2H₄N₄ and NH₄ Cl as precursors.Ag nanoparticles with different mass contents are deposited on g-C₃N₄ nanosheets to prepare Ag/g-C₃N₄ composite catalyst.The morphology,structure,chemical composition,specific surface area and optical properties of photocatalyst samples are characterized by SEM,EDS,AFM,XRD,FTIR,XPS,BET,UV-vis spectra,PL emission spectra,transient photocurrent response and EIS.The results show that the metal Ag nanoparticles of about 4 nm are successfully decorated on g-C₃N₄ nanosheet and the thickness of g-C₃N₄ nanosheet is about 1.06 nm,corresponding to only 3 layers of C-N atomic layer.The BET surface area of g-C₃N₄ nanosheet is 65.1 m2·g-1.Compared with g-C₃N₄,the absorption to visible light of Ag/g-C₃N₄ is significantly enhanced,and the transfer and separation of photogenerated carries become more effective.The experimental results demonstrate that the photocatalytic activity of Ag/g-C₃N₄ is the highest when the deposition amount of Ag nanoparticles is 5%.The photocatalytic activity of Ag/g-C₃N₄ composites can be effectively enhanced,mainly due to the synergistic effect of Ag nanoparticles and mesoporous g-C₃N₄ nanosheets.This method provides a new technique for the modification of g-C₃N₄.Secondly,the porous Ag/g-C₃N₄ bars are prepared one-step by calcining the driedmixture of C3H6N3 treated with HNO3 and AgNO3 aqueous solution.The morphology,microstructure,chemical composition and photoelectric properties are investigated.These results indicate that Ag nanoparticles have been successfully deposited on the g-C₃N₄ surface.The diameter of g-C₃N₄ bar is 1² μm with the length of up to tens of micrometers.Importantly,the rough and porous surface of g-C₃N₄ bar can provide more adsorptive and active sites for the photocatalytic reaction.Compared to bulk g-C₃N₄ and pure g-C₃N₄,Ag/g-C₃N₄ composites broaden the response range to visible light and enhance the absorption intensity,and have a more rapid separation and lower recombination rate of charge carries.The photocatalytic activity of Ag/g-C₃N₄ composite is highest when 5% Ag is loaded on the substrate.The RhB degradation rate in 240 min of 5% Ag/g-C₃N₄ is about 3.5 times that of bulk g-C₃N₄.The reason for the excellent photocatalytic performance of Ag/g-C₃N₄ composites is that the decorated Ag nanoparticles and mesoporous g-C₃N₄ matrix work well together.Synthesizing the mesoporous Ag/g-C₃N₄ composites in one step is fairly feasible and highly operational,which can effectively improve the photocatalytic performance.And it could be referred in further research on modifying the g-C₃N₄ photocatalyst.The reaction and adsorption sites increase by enlarging the specific surface area of g-C₃N₄ and the supporting a certain amount of noble metal Ag nanoparticles on the g-C₃N₄ surface,which enhance absorption and response on the visible light and promote transfer and separation of photocarrier,thus effectively improve the reaction activity of g-C₃N₄ photocatalyst.This work provides a new way to research and develope the highly active g-C₃N₄ and other photocatalysts.