Preparation And Visible Light Catalytic Performance Of G-C₃N₄ Based Composites

Graphite phase carbon nitride?g-C₃N₄?as a new semiconductor photocatalyst,with simple preparation conditions,abundant raw materials,stable chemical properties and excellent visible light response,has caused extremely attention of numerous scholars.However,the high recombination rate of electron-hole severely restricts performance.The g-C₃N₄ was prepared by thermal condensation,and then the g-C₃N₄ composite materials were prepared by surface modification and composite structure construction.The compositions,photocatalytic properties and structure of the composite photocatalyst were analyzed,and separation efficiency of electron-hole were also further investigated.?1?Cyano modified g-C₃N₄ photocatalyst was synthesized by salt assisted method.FT-IR and XPS indicated the formation of cyano group.The cyano modified g-C₃N₄ can adjust the band gap and enhance the absorption of visible light.The best hydrogen production performance of the catalyst is 1.5 times of that of g-C₃N₄,and it has better stability in the cycle of hydrogen production.In addition,PL and electrochemical tests show that cyano-modified g-C₃N₄ can effectively reduce the recombination rate of electron-hole.?2?Co₃O₄-g-C₃N₄ heterojunction complex and the ternary Co₃O₄/g-C₃N₄/C quantum dots heterojunction catalyst were prepared by solid phase and thermal decomposition method.Various characterization methods were used to indicate the existence of Co₃O₄ and verify the formation of heterojunction.UV-vis test shows that the band gap width of Co₃O₄-g-C₃N₄decreases,which is attributed to the formation of p-n heterojunction.HRTEM indicate that C quantum dots were tightly attached to g-C₃N₄ for Co₃O₄/g-C₃N₄/C.When the content of glucose is 0.35%,the hydrogen production rate is 11.51 times higher than that of g-C₃N₄.The results of PL,EIS and transient photocurrent reveal that p-n junction can effectively promote the separation of electrons and holes,and C quantum dots as electron transmission channels significantly improve the separation ability of electrons and holes.?3?The g-C₃N₄/PEI?polyethylenimine?/MoS₂ was prepared by electrostatic self-assembly.XRD and UV-vis show that PEI did not change the crystal structure and absorption properties of g-C₃N₄.The possible formation mechanism of g-C₃N₄/PEI/MoS₂ was researched by Zeta analysis.Rh B as simulated pollutants evaluated the photocatalytic performance.When the mass fraction of MoS₂ was 7%,the degradation rate can reach 78%.Electrochemical tests and PL indicate that the composite structure can accelerate the conduction of photogenerated electron holes and improve the separation efficiency.