Preparation And Visible-light Photocatalytic Properties Of Modified Mpg-C₃N₄ Materials

Solar photocatalysis by semiconductors has emerged as one of the most promising technologies in the field of the elimination of organic pollutants.Develop a novel highly efficient visible-light induced photocatalysts becoming a crucial research field.Graphitic carbon nitride（g-C₃N₄）has attracted extensive attention due to its smallest direct band gap that allows a maximal light absorption in the visible-light region.Mesoporous graphitic carbon nitride（mpg-C₃N₄）exhibited superior physicochemical properties,which can show potentiality in visible-light photocatalysis of application.Therefore,the modified research of mpg-C₃N₄ photocatalyst is significant.In this paper,based on research results and the current status of the photocatalyst,a series of modified mpg-C₃N₄ photocatalysts with enhanced visible-light photocatalytic activity are prepared.Contents are as follows:1.A series of Cu-doped mesoporous graphitic carbon nitride（Cu/mpg-C₃N₄）photocatalysts with Cu introducing from 0.1 to 5wt% were prepared using cupric chloride and melamine as precursors.The physicochemical properties of the synthesized samples were characterized by XRD,FT-IR,XPS,SEM,TEM,BET,DRS,and PL.The results indicate that embedded Cu2+changed the optical properties,affected the energy band structure,and increased the electron/hole separation rate.Subsequently,the photocatalytic activity of Cu/mpg-C₃N₄ was evaluated by methyl orange（MO）degradation under visible-light irradiation.The conversion of MO reaches to 90.3% in 120 min by Cu2+-doped mpg-C₃N₄.The rate constant for Cu2+-doped mpg-C₃N₄ was 2 times as high as that of pure g-C₃N₄.These results should usefully expand applications of mpg-C₃N₄ as a visible-light-driven photocatalyst.2.In order to develop highly efficient visible-light induced photocatalysts,the zinc oxide（ZnO）hybridized with mesoporous graphitic carbon nitride（mpg-C₃N₄）nanocomposite photocatalysts（mpg-C₃N₄/ZnO）were synthesized through simple one-step calcination in this paper.The physicochemical properties of the synthesized samples were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,high-resolution transmission electron microscopy（HRTEM）,N2 gas adsorption Brunauer-Emmett-Teller method（N2-BET）,UV-vis diffuse reflectance spectra（DRS）,and photoluminescence spectra（PL）.Subsequently,the photocatalytic performance of mpg-C₃N₄/ZnO was evaluated by photocatalyticdegradation of methyl orange（MO）aqueous solution under visible-light irradiation.The photocatalytic activities of the resultant mpg-C₃N₄/ZnO nanocomposites were enhanced outstandingly and much higher than that of pure mpg-C₃N₄ and ZnO.The improved photocatalytic activities of the mpg-C₃N₄/ZnO nanocomposites was ascribed to the exaltation of the separation efficiency of photoinduced electron-hole pairs,resulting from the heterojunction established between the interfaces of mpg-C₃N₄ and ZnO.3.To study the photocatalytic activity under visible light irradiation,a series of mesoporous graphitic carbon nitride（mpg-C₃N₄）/Ag₂ O photocatalysts were synthesized.The as-prepared photocatalysts were characterized with X-ray diffraction（XRD）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,N2 gas adsorption Brunauer-Emmett-Teller（BET）method（N2-BET）,Fourier transform infrared spectroscopy（FT-IR）,UV-vis diffuse reflectance spectra（DRS）,and photoluminescence spectra（PL）methods to determine their phase structure,purity,morphology,spectroscopic,and photoluminescence emission performance,respectively.Photocatalytic degradation of methyl orange（MO）aqueous solution under visible-light irradiation indicated that the mpg-C₃N₄/Ag₂O-50 nanocomposite has the best activity.Photocatalytic activity of this nanocomposite is nearly 5.0 and 3.4-folds greater than those of the pure mpg-C₃N₄,and Ag₂ O samples in degradation of methylene orange,respectively.The enhancement of photocatalytic activity was mainly ascribed to the enhanced visible-light absorption ability and the formation of p-n heterojunctions between counterparts of the nanocomposites,which promote the generation and separation of charge carriers.In addition,the experiment of different scavengers revealed that ·O2-and h+ were main active species in MO degradation.