Synthesis Of G-C₃N₄-based Nanocomposites And Their Visible Light Photocatalytic Performance

Photocatalytic technology exhibits a great potential for solving globe energy crisis and environmental pollution problems.Graphitic carbon nitrid（g-C₃N₄）has attracted a lot of attentions due to its good thermal and chemical stability,non-toxicity and low cost.However,the photocatalytic performance of bulk g-C₃N₄ is limited greatly due to its low specific surface area,low visible light absorption and high recombination efficiency of photogenerated electron-hole pairs.In this study,the g-C₃N₄ was synthesized by the calcination condensation method.The protonated g-C₃N₄（p-g-C₃N₄）was prepared by the protonation process.Then it was used as the substrates,the p-g-C₃N₄ were combined with the graphene oxide（GO）nanosheet and the Ag/AgCl nanoparticles by the sonochemical and deposition-precipitation method respectively.Finally,the g-C₃N₄ nanosheets were prepared by the thermal oxidation etching method.The structures,morphologies and optical properties of samples were characterized by XRD,TEM,XPS,UV-vis and PL methods.The visible light photocatalytic performances of samples were evaluated by photodegradation of methyl orange（MO）,tetracycline hydrochloride（TC）and ciprofloxacin（CIP）solutions under visible light irradiation.The results of the protonation showed that,the p-g-C₃N₄ possessed a thin layered structure after protonation.The absorption edges of p-g-C₃N₄ showed a increasing blue shift with the increased of hydrochloric acid concentration,and the separation efficiency of photogenerated electron-hole pairs were enhanced obviously when compared to the bulk g-C₃N₄.When the concentration of hydrochloric acid was 3 mol/L,the sample exhibited the highest visible light photocatalytic performance,and the photodegradation rate of MO solution was 30.08% after visible light irradiation for 2 h.The results of the GO/p-g-C₃N₄ nanocomposites showed that,the visible light absorption and the separation efficiency of photogenerated electron-hole pairs of GO/p-g-C₃N₄ nanocomposites were enhanced obviously when compared to the bulk g-C₃N₄.When the concentration of HCl was 3 mol/L,the GO/p-g-C₃N₄ nanocomposite achieved the highest photocatalytic performance,and the photodegradation rate of MO solution was 84.94% after visible light irradiation for 2 h.The photodegradation rate of TC solution was 92.43% after visible light irradiation for 4 h.Besides,the GO/p-g-C₃N₄ nanocomposites showed high photocatalytic stability.The results of the Ag/AgCl/p-g-C₃N₄ nanocomposites showed that,the visible lightabsorption and the separation efficiency photogenerated of electron-hole pairs of Ag/AgCl/p-g-C₃N₄ nanocomposites were enhanced obviously when compared to the bulk g-C₃N₄.When the amount of AgNO3 was 0.7 mmol,the Ag/AgCl/p-g-C₃N₄ nanocomposite achieved the highest photocatalytic performance,and the photodegradation rate of MO solution was 90.37% after visible light irradiation for 1 h.The photodegradation rates of TC and CIP solutions were 92.47% and 76.06% after being visible light irradiated for 2 h respectively.Besides,the Ag/AgCl/p-g-C₃N₄ nanocomposites showed high photocatalytic stability.The results of the thermal oxidation etching process showed that,the g-C₃N₄ nanosheets exhibited an amorphous structures after thermal oxidation etching process.The absorption edge of g-C₃N₄ sheet show a increasing blue shift with the increase of etching temperature,and the separation efficiency of photogenerated electron-hole pairs was enhanced obviously when compared to the bulk g-C₃N₄.When the etching temperature was 475 ℃,the g-C₃N₄ nanosheet achieved the highest photocatalytic performance,and the photodegradation rate of MO solution was 74.43% after visible light irradiation for 2 h.