Preparation Of Transition Metal Chalcogenides And Catalytic Properties Of Their Composite Structures

Two-dimensional transition metal chalcogenides（TMDCs）have the advantages of adjustable energy level structure,fast photogenerated electron migration rate,strong absorption capacity in the visible light range,and huge specific surface area,and are used in optoelectronic devices,nano The huge potential of enzymes,photocatalysis and other directions has become a hot spot of people’s attention in recent years.However,due to the chemical inertness of the base plane of the two-dimensional TMDCs and the rapid recombination of photogenerated electrons and holes,the application in the field of light energy conversion is inhibited.Generally speaking,creating a composite structure on the base surface is one of the effective ways to improve the light energy conversion ability.At the same time,the controllable equipment of two-dimensional TMDCs is a prerequisite for high-efficiency applications,and it has been facing great challenges.Among many processes,chemical vapor deposition（Chemical Vapor Deposition,CVD）is an effective method for growing layer thickness and size controllable,high-quality TMDCs,but CVD technology still has shortcomings in terms of source stability and growth uniformity.How to achieve the controllable growth of two-dimensional TMDCs on different substrates through effective ways is an urgent problem to be solved.Based on the above analysis,this paper uses secondary granulation assisted CVD to prepare two-dimensional TMDCs materials,and further constructs MoSe₂/Porous carbon nanoplates（MoSe₂/PCN）composite structure to study the catalytic properties of light-regulated nanoenzymes.Realize the efficient conversion and utilization of solar energy.To this end,this article carries out the following two researches:1.In this paper,a novel secondary granulation assisted CVD growth method is designed to regulate the sublimation amount of the high melting point oxide source and ensure the uniform supply of the metal reaction source to achieve the appropriate ratio of the metal source to the sulfur powder.Two-dimensional WS₂,Nb S₂and Ti S₂of different sizes and morphologies can be grown on Si O₂/Si substrates.Using photoluminescence spectroscopy（PL）,Raman spectroscopy（Raman）,high-resolution transmission scanning electron microscopy（HRTEM）and other testing methods,it has been verified that after process optimization,high-quality single-layer WS₂Film of more than 50 microns can be grown at about 750°C.At the same time,it is found in the experiment that after the secondary granulation of WO₃particles,WO₃particles of different particle sizes will change the supply of tungsten precursors,so as to controllably adjust the nucleation density,film size and morphology of WS₂.Finally,through the specific surface area test（BET）and X-ray photoelectron spectroscopy（XPS）test,combined with the sintering characteristics of the oxide powder,the growth mechanism was systematically analyzed.In addition,two-dimensional Ti S₂and Nb S₂can be synthesized under the same growth conditions,with the same changing law,indicating that the method has a certain scalability,and further verified that the secondary granulation-assisted CVD growth method has a certain scalability.2.In this paper,a one-step CVD method was used to synthesize MoSe₂/PCN composite structure on a sodium chloride crystal substrate,and the enzyme-like catalytic activity under light regulation was studied.First,the sodium chloride crystal substrate coated with glucose is prepared by recrystallization,and then the MoSe₂/PCN composite structure is synthesized in one step through the secondary granulation assisted CVD growth method.Using SEM,TEM,XRD,XPS and other characterization methods to analyze the structure,morphology,composition and other properties of the catalyst,the results show that the use of the second granulated Mo O₃particles as the precursor can make the thin layer of MoSe₂uniformly grow on the PCN surface.Then,using o-phenylenediamine（OPD）as a nanoenzyme catalytic substrate,the peroxidase-like catalytic activity of the single-component MoSe₂,PCN and MoSe₂/PCN composite structure under light conditions was compared.The study found that the enzyme kinetic behavior of the sample conformed to the Michaelis equation,and the maximum reaction rate（Vmax）after compounding reached 17.81μM min^-1,which was 4.7and 3.7 times that of MoSe₂and PCN,respectively.Finally,through the comparative analysis of the characterization results of Fourier infrared spectroscopy,solid absorption,and active substance detection,it is found that the high catalytic activity of the composite structure comes from the following aspects:it has a large specific surface area,and its own defects provide a lot of The active sites,the abundant hydroxyl functional groups on the sample surface adsorb a large number of reaction substrates,and the appropriate energy level structure and strong visible light absorption capacity make it generate more·OH.