Construction Of Photocatalyst Based 2D Material Mxenes And Its Photocatalytic Performance Study

With the rapid development of society,environmental pollution and energy shortage are two major problems that have been plaguing us.Photocatalysis can provide a promising and environmentally friendly approach to solve the global pollution problem and reduce the dependence on fossil fuels.However,the performance of singlecomponent photocatalysts is limited due to the rapid recombination of photoexcited carriers and insufficient active centers.So,it is necessary to construct efficient composite photocatalysts.In recent reports,MXenes are considered as promising new materials for photocatalytic processes,and it is an attractive 2D material because of its many advantages such as high chemical and mechanical stability and good electrical conductivity.In addition,MXenes surface can be functionalized with various chemical groups.These advantages make MXenes an excellent two-dimensional electron mediator.In this paper,using 2D Ti₃C₂ Mxene as the electron mediator,three types of Z-scheme heterojunction 2D nanomaterials have been constructed.The performance of the photocatalysts was then evaluated by degradation of tetracycline hydrochloride（TC-HCL）and photocatalytic hydrogen production under visible light irradiation as follows:（1）2D/2D/2D materials are widely used in photocatalysis owing to the advantages of high specific surface area,large contact interface,numerous charge transfer channels and ultrashort charge transfer distance.In this work,2D/2D/2D Bi₂WO₆/Ti₃C₂/Sn Nb₂O₆catalysts were successfully constructed via an anaerobic hydrothermal method.As ultrathin 2D Ti₃C₂MXene served as an electron mediator,Z-scheme heterojunction was formed through Ti-O-Bi interface or the combination of2D Sn Nb₂O₆,2D Bi₂WO₆ and Ti-O-Sn interface bond,which could afford charge transfer channels and increase reactive sites.As a result,the Bi₂WO₆/Ti₃C₂/Sn Nb₂O₆composites significantly improved the photodegradation efficiency of TC-HCL due to the high redox ability,and its degradation efficiency in 90 minutes was 7.93 times that of Sn Nb₂O₆.This work provides an effective method to construct 2D/2D/2D Z-scheme heterojunction by tight chemical bond.（2）The construction of heterojunctions is usually considered as the main technological means to produce hydrogen from solar-driven photocatalytic hydrogen production.Among them,Z-scheme heterojunction photocatalysts have received increasing attention in the field of overall water splitting.We have constructed2D/2D/2D Bi₂WO₆/Ti₃C₂/g-C₃N₄ ternary Z-scheme photocatalyst by simple hydrothermal method and electrostatic self-assembly using active g-C₃N₄ as the reduction site,titanium carbide（Ti₃C₂）as the electron mediator and bismuth tungstate（Bi₂WO₆）as the oxidation site.The photocatalytic hydrogen production activity and stability of different samples under visible light（λ≥420 nm）irradiation were investigated.The results showed that the hydrogen production rate of the 3%Bi₂WO₆/Ti₃C₂/g-C₃N₄ composite was 176μmol·h^-1·g^-1,which was 2.33 times higher than that of the pure phase g-C₃N₄.In addition,the catalyst remained highly active and showed good stability after several cycle tests.This study may provide new insights for the practical application of photocatalytic hydrogen production.（3）ZnIn₂S₄ is a novel two-dimensional visible light responsive photocatalyst that has attracted much attention in the photocatalytic evolution of H₂ under visible light irradiation due to its attractive intrinsic photoelectric properties and geometrical configuration.However,ZnIn₂S₄ still suffers from severe charge recombination,resulting in its poor photocatalytic performance.Herein,2D/2D/2D WO₃/Ti₃C₂/ZnIn₂S₄ ternary Z-scheme photocatalyst were successfully constructed.The photocatalytic hydrogen evolution efficiency of nanocomposites with different proportions was evaluated under visible light irradiation.The photocatalytic efficiency of 20%WO₃/Ti₃C₂/ZnIn₂S₄ was the highest,with a hydrogen production rate of7391.97μmol·h^-1·g^-1,which was 7.1 and 3.5 times higher than that of pure ZIS and20%TC/ZIS,respectively.The enhanced photocatalytic activity is mainly due to the tight interfacial contact between the WO₃,Ti₃C₂ and ZnIn₂S₄ nanosheets,which promotes the transfer and separation of photogenerated electrons.This study provides a new idea for the preparation of efficient,stable,and durable 2D/2D/2D heterojunction photocatalysts for solar energy conversion.