Research On The Preparation And Photocatalytic Performance Of Carbon Nitride Based Composite Catalysts

In recent years,photocatalytic technology has attracted considerable attentions in organic pollutant remediation and clean energy production.Graphitic carbon nitride?g-C₃N₄?has been widely used in the field of photocatalysis due to its high stability,low cost and special electronic band structure.In this paper,in order to further expand the application of g-C₃N₄ in environmental pollution,three novel,efficient and stable composite catalysts have been developed.The main contents and results are as follows:The Bi₂MoO₆/g-C₃N₄ composite catalysts with different pH were prepared by an ultrasonic impregnation method.The photocatalytic properties of rhodamine B?RhB?were evaluated by XRD,FT-IR,TEM,BET,UV-vis and so on.The results showed that compared with monomer,Bi₂MoO₆/g-C₃N₄ composite exhibited superior photocatalytic activity due to the effective separation of the photo-generated electron-hole pairs,and the different pH values can lead to different photocatalytic performance.The g-C₃N₄ with different sulfur contents were prepared by thermal polycondensation approach,and the ZnTNPc/g-CNS?zinc-tetranitro phthalocyanine/sulfur-doped carbon nitride?composite photocatalyst was synthesized.XRD,TEM,TG,XPS and EPR were used to characterize the structure and morphology of the catalysts.The results showed that the addition of S facilitated the formation of lattice defect over the g-C₃N₄,which can promote the separation of photogenerated electron-hole pairs and increase the specific surface area of g-C₃N₄.The ZnTNPc/g-CNS90 composite exhibited the highest photocatalytic activity and superior stability for the photocatalytic degradation of methylene blue?MB?under the visible light irradiation.In addition,the possible mechanism of the degradation of MB solution was further explored.Based on above study,the effects of different phthalocyanine substituents on the photocatalytic performance were investigated.ZnPc/g-CNS?zinc phthalocyanine/sulfur-doped carbon nitride?,ZnTNPc/g-CNS?zinc-tetranitro phthalocyanine/sulfur-doped carbon nitride?and ZnTCPc/g-CNS?zinc-tetra-carboxy phthalocyanine/sulfur-doped carbon nitride?composites were synthesized and characterized by XRD,FT-IR,TEM,UV-vis and so on.The photocatalytic degradation of MB over the substituent phthalocyanine was better than that of the unsubstituted phthalocyanine.The strong electron-withdrawing group can optimize the band structure of phthalocyanine,which was more favorable for the photocatalytic reaction.The mesoporous carbon nitride?MCN?was prepared by using SBA-15 as template,the SnS₂/MCN,CoS₂/MCN and different quality ratio of SnCoS₄/MCN catalysts were synthesized by in-situ growth method.The structure,morphology and optical properties of the samples were characterized by XRD,TEM,UV-vis,EDS and PL.The results showed that SnCoS₄/MCN?0.5?showed the best photocatalytic performance.The photocatalytic mechanism found that ·OH,h+ and ·O2-was an active intermediate species in the process of degrading MB.