Study On The Effect Of Precursor On Microstructure And Synergetic Photocatalysis Activity Of G-C₃N₄

As a new type of metal-free organic semiconductor photocatalyst,carbon nitride has emerged as an attractive and ideal material for environmental treatment in recent years.In this paper,three graphite carbon nitride?g-C₃N₄?,namely g-C₃N₄-U,g-C₃N₄-C and g-C₃N₄-M were prepared.The microstructure,morphology and properties of obtained samples were characterized by XRD,FTIR,SEM,TEM,BET,XPS,EPR and UV-vis DRS.Then,the potential application of g-C₃N₄ in the synergetic photocatalysis that reduction of Cr?VI?and oxidation of sulfosalicylic acid?SSA?was further explored.The effect of different factors such as the dosage of catalyst,initial pH and concentration ratio of Cr?VI?with SSA on the synergetic photocatalysis was also investigated.Moreover,the effect of precursors on the microstructure of g-C₃N₄ and the mechanism of synergetic photocatalytic were contrastively studied.Results were shown as follows:?1?Through the method of pyrolysis,g-C₃N₄-U,g-C₃N₄-C and g-C₃N₄-M were successfully synthetized using urea,cyanamide and melamine as three different precursors,respectively.Although these samples were found with good graphite-like structure,the microstructures of these g-C₃N₄ were much different.?2?When the catalyst dosage was 0.5 g/L,pH=2,the initial concentration ratio of Cr?VI?and SSA was 1:4?10 mg/L:40 mg/L?,optimal synergetic photocatalysis efficiency was achieved,which was more than 3 times higher than the reaction efficiency of separated photoreduction or photooxidation.Within 3 hours illumination,the Cr?VI?reduction ratio together with the oxidation ratio of SSA could reach 98.9% and 93.4%,respectively.?3?The mechanism of synergetic photocatalysis was that Cr?VI?was reduced by electrons and SSA was oxidized by the combined function of hole,O2·-and ·OH at the same time under visible light.Simultaneous reaction of photoreduction and photooxidation could promote the separation of photogenerated electron and hole,thus greatly improved the photocatalytic activity of g-C₃N₄.?4?Among the microstructure diversity caused by different precursors,hydrogen bonds and oxygen-doped microstructures were the main factors that affect the photocatalysis of g-C₃N₄.With smaller amount of hydrogen bonds and more oxygendoped microstructures,fast charge transfer between interlayers and the activation of oxidized radicals could be achieved,which contributed to improve the photocatalytic activity of g-C₃N₄.This study helped researchers furtherly understand the effect of precursor on the microstructure of g-C₃N₄,and provided theoretical support for the application of gC₃N₄ synergistic photocatalysis technology in the wastewater treatment.