| The catalyst plays an important role in the development of the chemical industry and it is related to all aspects of people's lives.It is one of the hot topics in the field of materials research.In 2011,the platinum monoatomic catalyst Pt1/FeOx produced by Zhang Tao's research team brought catalytic research to the monoatomic field,realizing that the most ideal state of adsorption is that atoms are homogeneous,uniformly distributed on the surface of the substrate and can be more efficient.Play catalytic activity.The design and preparation of high-efficiency catalysts require comprehensive consideration of many factors,among which the choice of substrate is particularly important.In 2009,graphite-like phase carbon nitride?g-C3N4?was discovered,which may be a good substrate material due to its chemical stability and special void structure.The two-dimensional g-C3N4 crystal consists of a triazine ring?C3N4?or heptazine ring?C6N7?formed by sp2-hybridized C and N elements,and connects the ring and the ring through n atoms to form an infinitely large plane.Based on the above factors,this article mainly focuses on the two-dimensional triazine structure-like graphite phase carbon nitride?gt-C3N4?crystals.Based on the density functional theory,the first-principles calculation method was used to analyze the fourth cycle.The geometric structure,electronic properties,adsorption and diffusion of the element over two-dimensional?gt-C3N4?crystal surface,and the catalytic oxidation of monoatomic catalyst Ti/gt-C3N4 by CO,the structure of the full text is as follows:The first chapter briefly introduces the importance of current catalysis research and the development in recent years.At the same time,the advantages and disadvantages of monoatomic catalysts,the high-efficiency catalytic performance of monoatomic catalysts,the relationship between supports,and the structural properties of carbon-like carbon nitrides and their feasibility as a substrate are described.The second chapter is mainly about the first-principles method,the density functional theory and the software and software package used in the calculation process.In the third chapter,taking the two-dimensional gt-C3N4 crystal structure as the research object,the first-principles method based on the density functional theory is used to study the geometric structure of the fourth periodic transition metal atom on the surface of the two-dimensional gt-C3N4 crystal structure,adsorption and diffusion.It was found that the fourth-cycle transition metal atoms were adsorbed on the surface of two-dimensional gt-C3N4 crystals.Except for zinc?Zn?,nickel?Ni?and copper?Co?,the adsorption energy of other metal atoms was comparable to the corresponding formation energy.It is relatively large and can be relatively stable in adsorption.Among the relatively stable metal atoms,only the titanium?Ti?,iron?Fe?and cobalt?Co?atoms have a relatively large diffusion barrier after adsorption.Diffusion is easy,and other adsorbed atomic diffusion barriers are small and easily diffused.In the fourth chapter,the effect of Ti-catalyzed oxidation of Ti/gt-C3N4 on monoatomic catalysts was studied by using the folded structure of two-dimensional GT-C3N4 crystal as the base material.As a result,it was found that the substrate material preferentially adsorbed O2,and then the reaction barrier with gaseous CO was about 2.68 eV.It was difficult to find a relatively stable transition state when co-adsorbed with CO,but the intermediate state formed a reaction barrier of about0.17 eV.It can be seen that the first CO2 is released as a co-adsorption reaction;the?atoms remaining on the base material continue to react with CO,and the barriers to react with gaseous CO and co-adsorb CO are about 0.36 eV,respectively.And 0.94eV,but the initial energy is about 0.45eV higher than the co-adsorption.Therefore,it will eventually be carried out in the form of the reaction of?atoms with gaseous CO molecules.The fifth chapter summarizes the full text. |
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