Study On The Preparation Of MXene Phase Mb₂CTx And Its Composite Materials And The Performance Of Photolysis Of Water For Hydrogen Production

Governments and enterprises of various countries are actively promoting energy reforms to develop clean and efficient hydrogen energy,in order to replace the non-renewable energy sources that causes pollution to the living environment.In recent years,with the vigorous support and development of electric and hydrogen vehicles,it is injected power into the photocatalytic water splitting hydrogen evolution under the state of scientific research.However,the difficulty of this technology be determined efficient photocatalysts.MXene,with the two-dimensional structure,conductivity,hydrophilicity,and abundant active sites which make it become potential best candidates for cocatalysts.As one of them,Nb2 CTx,is less in photocatalysis research and has a higher work function(4.1 e V).The preparation of 2D Nb2CTx-based heterojunction photocatalysts with adjustable morphology and structure is expected to further improve the hydrogen evolution activity of water splitting.Therefore,this work obtains a two-dimensional structure of MXene phase Nb2 CTx under HF etching firstly,and then adopts electrostatic self-assembly method to build a 1D/2D and 2D/2D heterojunction Cd S and Nb2 CTx composite photocatalysts.The performance of photocatalytic water splitting to hydrogen evolution is further discussed.(1)High-purity MAX phase Nb2 Al C is receive through high-temperature solid-phase sintering,the length of the HF etching time is controlled,the Al layer is selectively etched out of the Nb2 Al C,and then Dimethylsulfoxide(DMSO)is used for intercalation.The XRD test showed that after etching for 120 h,the(002)crystal plane moved at a low angle of 2? ? 7.5 °C,indicating that the Nb2 CTx phase of the MXene phase was successfully transformed.The corresponding SEM,TEM and AFM results demonstate the successful preparation of twodimensional(2D)nanosheets with a layer thickness of about 3 nm.XPS results showed the presence of(-O,-OH and-F)groups on the surface of Nb2 CTx.High-strengh etching will cause damage to the Nb2 CTx nanosheet structure and generated Al F3 particles,which is not conducive to obtaining 2D nanosheet Nb2 CTx.It is proved in another set of etching experiments with high concentration and long time.Therefore,the concentration of the etching solution,as well as the etching temperature and time should be fully consideres when performing etching experiments.(2)1D/2D heterojunction Cd S/Nb2 CTx nanocomposite catalysts are successfully constructed under the action of electrostatically driven self-assembly.In the morphological characterization of SEM and TEM,the morphological characteristics of one-dimensional Cd S nanorods and the close growth of Cd S nanorods on the surface of two-dimensional morphology Nb2 CTx are confirmed.The corresponding crystal structures and chemical components from XRD,FTIR and XPS composition testing further demonstrates the successful construction of 1D/2D heterojunctions,The XPS surface chemical state results show that-F groups on the surface of Nb2 CTx are replaced by-OH or-O in solvothermal synthesis.The successful construction of the Schottky junction of the 1D/2D composite system and the formation of the Schottky barrier can benefit the transport of photogenerated charges from Cd S to Nb2 CTx,effectively reduce the probability of charge carrier recombination and accelerate the photocatalytic reaction process.(3)The construction of 2D/2D heterojunction materials will be contributing to larger-area interface contact.The 2D Cd S/2D Nb2 CTx composite catalysts is still successfully prepared by electrostatic self-assembly.TEM and AFM micromorphological characterization showed that two-dimensional(2D)Cd S is successfully prepared.In situ fabrication of 2D Cd S nanosheets/2D Nb2 CTx MXene nanosheet Schottky junction.The full-spectrum absorption characteristics of Nb2 CTx make the composite sample exhibit enhanced light absorption,which is beneficial to the utilization of sunlight.Layer-to-layer contact is more conductive to the rapid transfer of photogenerated charge to the surface of Nb2 CTx and rapid reaction with adsorbed protons.Compared with Cd S,it shows excellent hydrogen evolution activity.When Nb2 CTx is added at 40 mg,the hydrogen evolution rate is 5040 ?mol g-1 h-1,which is 4.3 times that of single Cd S.Therefore,the introduction of MXene phase Nb2 CTx,nanostructured Cd S,and the fabrication of 2D/2D schottky junction are the main factors for excellent photocatalytic activity.