Preparation Of Carbon Nitride Nanosheet-based Novel Photocatalysts And Their Visible Light Photocatalytic Activities

The development of new efficient semiconductor photocatalytic materials is an important prerequisite for the practical application of photocatalytic technology in photocatalytic decomposition of aquatic hydrogen and photocatalytic degradation of pollutants.Graphite phase carbon nitride?g-C₃N₄?nanosheet is a two-dimensional structure photocatalytic material,which has the advantages of visible light absorption,suitable band position,stable physical and chemical properties and low cost.However,single carbon nitride materials still have problems such as narrow visible light absorption,photoelectron and hole recombination,which limits their large-scale applications.In view of the above problems in the g-C₃N₄ nanosheet,a new carbon doped g-C₃N₄ nanoscale,g-C₃N₄/KCa₂Ta₃O₁₀ nanosheet heterojunction material and RGO/CdIn₂S₄/g-C₃N₄ ternary composite have been constructed by non-metallic elements doping and constructing heterojunction strategy.The activities of hydrogen production and degradation of pollutants by visible light photocatalytic catalysis are studied.The mechanisms of photocatalytic action were also investigated.The specific research contents are as follows:1.A new preparation method of carbon doped g-C₃N₄ nanoscale photocatalytic material with glucose as precursor was developed.The characterization results of XRD,FTIR and XPS showed that carbon was uniformly doped into g-C₃N₄ nanosheet materials.UV-DRS spectra show that carbon doping significantly broadens the visible light absorption range of carbon nitride materials.The photocatalytic activity of visible light hydrogen production of the prepared carbon doped g-C₃N₄ nanoscale reached 40.37?molh^-1 and the activity was 2.9 times of pure g-C₃N₄.The result of the fluorescence and photochemical characterization showed that the increase of hydrogen production activity in the carbon self-doped g-C₃N₄ was mainly due to the broadening of the visible light absorption and the enhanced separation of photogenerated carriers induced by carbon self-doping.2.g-C₃N₄/KCa₂Ta₃O₁₀ nanosheet heterojunction photocatalysts were prepared by a simple hydrothermal method.By changing the amount of precursors,the nanosheet heterojunctions of different proportions were constructed.The prepared KCa₂Ta₃O₁₀and g-C₃N₄ form a good two-dimensional 2D-2D heterogeneous interface.The photocatalytic hydrogen evolution under visible light of g-C₃N₄/KCa₂Ta₃O₁₀nanosheetheterojunctionwassignificantlyimproved.Amongthem,30%-g-C₃N₄/KCa₂Ta₃O₁₀ composite showed a high photocatalytic hydrogen production efficiency of 647.19.mol/g,which is 2.07 times than that of pure g-C₃N₄photocatalyst.The results of fluorescence and photochemical characterization showed that the efficiency of photoinduced charge separation in the nanoheterojunction was significantly higher than that of the bare nanosheet material,which is the main reason for the enhancement of the photocatalytic activity for hydrogen production.3.RGO/CdIn₂S₄/g-C₃N₄ ternary composite photocatalyst was synthesized by a hydrothermal synthesis.The structure characterization results show that well-defined heterostructure were formed between the RGO and CdIn₂S₄ nanoparticles and g-C₃N₄nanosheet materials.The visible light absorption performance of the RGO/CdIn₂S₄/g-C₃N₄ ternary system was significantly improved.The prepared RGO/CdIn₂S₄/g-C₃N₄ ternary composite has strong visible light photocatalytic performance.The degradation rate of tetracycline hydrochloride is 74.02%,which is obviously higher than that of CdIn₂S₄/g-C₃N₄,RGO/CdIn₂S₄,RGO/g-C₃N₄ binary material and bare CdIn₂S₄ and g-C₃N₄ materials.The enhanced photocatalytic activity is mainly attributed to the higher charge separation and transfer efficiency of the ternary heterojunction.In addition,photocatalytic mechanism results showed that hole and superoxide free radicals are main active species for the degradation of tetracycline hydrochloride.