Fabrication Of Graphite-like Carbon Nitride-based Nanocomposite Photocatalysts And Performance On Dyes Degradation Under Visible Light

Water pollution is now becoming incresingly serious with the economic and social development,additionally,the abuse of dyes increase the shortage of freshwater.Dye wastewater not only caused serious damage to water resources,but also posed a certain threat to human health.For the livelihood and development,the dye wastewater must be strictly treated.Apart from avoiding the discharge of dye wastewater,it is meaningful to seek for environment friendly and green technology to deal with the it.In this paper,we simply analysed and summarized the current dye wastewater treatment technology all over the world and put forward the excellent and promising technology of photocatalysis in the field of the global energy and environmental problem.Photocatalysis technology has the advantages of low cost,green initiative and simple operation,etc.,which is widely considered as an excellent and promising technology to degrade and mineralize the dyewastewater.Inorganic metal-free polymer semiconductor carbon nitride?g-C₃N₄?has attracted wide attention because of its distinct electronic band structure,chemical stable and low cost.However,the practical application of g-C₃N₄ was greatly limited due to the low quantum efficiency.g-C₃N₄ can be compounded with the suitable photocatalyst to construct heterojunctions.The formation of heterojunction is beneficial for the transfer and separation of photogenerated charge carriers,which suppresses the recombination of photogenerated electrons and holes and improves its quantum efficiency.In this paper,g-C₃N₄/CdWO₄,MnWO₄/g-C₃N₄,g-C₃N₄/O-doped Zn In₂S₄ heterojunction were successfully prepared by hydrothermal method and their photocatalytic performance were evaluated by degradation of dyes.The main achievements are the following three aspects:?1?Novel visible light responsive g-C₃N₄/CdWO₄ photocatalysts were formed by hydrothermal process.The results revealed that the interface interaction between CdWO₄ and g-C₃N₄ was recognized via CdWO₄ nanorod loading on the surface of the layered g-C₃N₄,improving the separation and transfer of the photoexcited hole and electron pairs.The photocatalytic activity of the g-C₃N₄/CdWO₄ was enhanced in comparison with pure g-C₃N₄ and CdWO₄.When the content of CdWO₄ in the heterojunction is 20%,the composite exhibits the best degradation performance.The degradation rate of Rhodamine B is 90% for 3 h under visible light,which showed great decolorization effect.After four cycles,the degradation efficiency of rhodamine B for g-C₃N₄/CdWO₄ composite did not decrease significantly,demonstrating the good stability of the heterojunction.The degradation mechanism of g-C₃N₄/CdWO₄ was proposed by species trapping experiments and ESR.?2?we firstly construct a novel solid-state Z-scheme MnWO₄/g-C₃N₄ nanocomposites via the facile hydrothermal method,showing that flowerlike MnWO₄ uniformly anchoring on the surface of g-C₃N₄.When the loading amount of MnWO₄ was 10%,the photocatalytic activity was the optimum,which was 2.3 times and 12.7 times higher than that of pure g-C₃N₄ and MnWO₄.The degradation rate of rhodamine B was 73% over 10% MnWO₄/g-C₃N₄ heterojunction during 4 h visible light irradiation,showing a good decolorization effect.After four cycles,the photocatalytic activity of heterojunction over rhodamine B did not significantly reduce,exhibiting excellent stability of MnWO₄/g-C₃N₄ heterojunction,which is beneficial to industrial applications.The degradation mechanism of MnWO₄/g-C₃N₄ was proposed by species trapping experiments and ESR.?3?The g-C₃N₄/O-doped Zn In₂S₄ nanocomposites were prepared by hydrothermal method.The presence of lattice oxygen in ZnIn₂S₄ was confirmed by XPS.HRTEM confirmed that the flaky oxygen-doped ZnIn₂S₄ successfully supported on the surface of the layered g-C₃N₄.When the loading amount of g-C₃N₄ is 20%,the composite material exhibits the best degradation rate over Rhodamine B.The degradation rate of rhodamine B over 20% g-C₃N₄ /O-doped Zn In₂S₄ was 97%,which showed a good photocatalytic performance.After four cycles,the degradation effect did not obviously decrease,which showed the great stability of photocatalyst.