Preparation And Properties Of Graphite-Like Carbon Nitride-Based Composite Photocatalysts

Visible-light catalysis technology,as a technology of environmental pollution,has received much attention at present.There are some problems to be solved urgently,such as high electron-hole recombination rate,poor conductivity,and narrow light absorption range.In this dissertation,starting from the improvement of photocatalytic activity,a series of photocatalytic materials with high photocatalytic activity and excellent stability were designed and synthesized to overcome the low photocatalytic efficiency of traditional catalysts and achieve efficient photocatalytic degradation of pollutants.The content is as follows:1)AgVO₃ nanowire was prepared by hydrothermal method and g-C₃N₄/AgVO₃ nanowire photocatalyst was synthesized through coprecipitation technique.The results showed that the g-C₃N₄ nanocrystals are uniformly dispersed on the surface of the AgVO₃ nanowires,which broadens their response to visible light,increases their specific surface area,and accelerates the separation of photogenerated electrons and holes,resulting in photocatalytic efficiency.After being effectively irradiated,the degradation rate of rhodamine B（Rh B）could reach100%after light irradiation（λ>400 nm）for 20 min.2)Graphitic carbon nitride quantum dots（CNQDs）,metal Ag nanoparticles and Bi₂MoO₆ were composited to prepare CNQDs/Ag/Bi₂MoO₆ ternary nanocomposite heterostructures.The results showed that the addition of Ag and g-C₃N₄ effectively can extend the visible light absorption range of the catalyst,increas its specific surface area accelerate the transfer rate of photogenerated charge,thus improving its photocatalytic performance.The enhanced performance is attributed to the formation of the ternary composite system.The degradation rate of Rh B by CNQDs/Ag/Bi₂MoO₆ after 30 min of visible light irradiation（λ>400 nm）is 100%.At the same time,according to the capture experiments,it is proved that h⁺and·O₂^-are the main active species in the photocatalytic degradation of CNQDs/Ag/Bi₂MoO₆composite under visible light irradiation of Rh B.3)The CNQDs,InVO₄ and BiVO₄ were prepared to produce leaf-like CNQDs/InVO₄/BiVO₄ ternary composite heterostructures.The results showed that the addition of g-C₃N₄effectively extends the visible light absorption range of the catalyst and increases its visible-light absorbtion efficiency,surface area,and due to the formation of a ternary semiconductor heterojunction,effectively inhibited the recombination of photogenerated electron-hole pairs,resulting in a significant improvement in its photocatalytic performance,which is due to the formation of a ternary semiconductor heterojunction.After 40 min of visible light irradiation,the degradation rate of Rh B was up to 100%.·O₂^-is a photocatalytically reactive species.4)The leaf-like BiVO₄ was prepared by hydrothermal method,Ag and g-C₃N₄ were deposited on the surface of leaf-like BiVO₄ to synthesize g-C₃N₄/Ag/BiVO₄ composite photocatalyst.The results showed that the addition of Ag and g-C₃N₄ effectively can extend the visible light absorption range of the catalyst,increased its specific surface area,and accelerat the transfer rate of the photogenerated charge due to the formation of a ternary heterostructure,resulting in its photocatalytic performance.The degradation rate of Rh B can reach 100%within 30 min of visible light irradiation（λ>400 nm）.Furthermore,the main active species were·O₂^-and·OH based on active species trapping experiments.