Study On Preparation And Catalytic Performance Of MXene Based Photocatalyst

With the improvement of human society’s awareness of health and sustainable development,people pay more and more attention to the problem of environmental pollution,especially the problem of water pollution.Semiconductor photocatalysis technology has been widely used in the treatment of pollutants in water because of its green,economic,high efficiency and other advantages.Narrow band gap semiconductor ternary sulphides,such as Cd In₂S₄and Zn In₂S₄,have become one of the most popular photocatalysts due to their low toxicity and cost and chemical stability,but their low photocatalytic activity was limited by the ease of rapid recombination of electron-hole pairs in single component semiconductors.To ameliorate this defect,this study introduces Ti₃C₂,a two-dimensional co-catalyst with excellent physicochemical properties,and uses a simple hydrothermal and solvothermal method to produce three new composite photocatalysts using Ti₃C₂,a two-dimensional lamellar material,as a substrate.Cd In₂S₄/Ti₃C₂complexes,Zn In₂S₄/Ti₃C₂complexes and Cu:Zn In₂S₄/Ti₃C₂complexes.The photocatalytic activity of the composite catalysts for antibiotics（tetracycline hydrochloride and 7-aminocephalosporanic acid）and heavy metals（Cr（Ⅵ））was tested under visible light conditions.The details of the study are as follows:（1）Ultrathin Ti₃C₂nanosheets were fabricated using a mixture of Li F and HCl as etchant,and Cd In₂S₄/Ti₃C₂composite photocatalysts consisting of Cd In₂S₄microspheres and ultrathin nanosheets were synthesized by a solvothermal method.The Cd In₂S₄surface in the composites exposed more highly reactive crystalline surfaces,which resulted in high photocurrent and low impedance compared to pure Cd In₂S₄,and significantly improved photocatalytic performance.The optimum degradation rate constants k for Cr（Ⅵ）and tetracycline hydrochloride of the composites were 0.02999 min^-1and 0.01203 min^-1,respectively,which were 2.492and 2.443 times higher than those of pure CdIn₂S_4.（2）The ZnIn₂S₄/Ti₃C₂composite photocatalyst was synthesized by hydrothermal method using HF（≥40%）solution as etching agent to produce Ti₃C₂nanosheets.Under visible light irradiation,the optimised composite photocatalysts degraded 50 mg/L tetracycline hydrochloride and 25 mg/L 7-aminocephalosporanic acid with 91%and 95%efficiency in 120 min and 90 min respectively.The introduction of Ti₃C₂not only increased the visible light absorption and specific surface area of Zn In₂S₄,but also effectively separated photogenerated electrons and holes.After multiple cycles,the composite photocatalyst still exhibited excellent physicochemical stability and high photocatalytic activity.（3）Cu-doped ZnIn₂S₄nanoflowers were synthesized in situ on ultrathin nanoflakes of Ti₃C₂.Excessive loading of Cu will affect the production of Zn In₂S₄.The doped Cu enhances the carrier density and charge transfer efficiency,and the Cu:Zn In₂S₄composite photocatalyst containing 1%Cu has the best visible light photocatalytic performance for the complete reduction of Cr（Ⅵ）within 40 min.With the further introduction of Ti₃C₂,the Cu:Zn In₂S₄nanoflower has a good interfacial contact with Ti₃C₂,prompting Ti₃C₂to become an electron collector and transporter,effectively extending the lifetime of the photogenerated carriers,leading to a reduction of the composite photocatalyst to 30 min for the complete reduction of Cr（Ⅵ）.