Design Of Two-dimensional Layered W₂N₃ Supported Metal Clusters And Theoretical Study Of Nitrogen Reduction Catalytic Performance

Since the industrial revolution,coal,oil,natural gas and other fossil energy have occupied the world’s main energy supply sources,which are not renewable once used up.At the same time,the massive use of fossil energy will cause global warming,and some toxic substances discharged will affect the ecological cycle,affecting the health of life on earth.To change the existing energy structure,we need to make efforts and research in many aspects.For example,we need to improve the preparation method of the existing chemical industrial products with high energy consumption and high pollution.To find suitable,efficient,clean and sustainable energy to replace traditional fossil energy;And research and development of efficient energy storage materials and devices.The improvement of these aspects is inseparable from the in-depth study of chemical reaction mechanism,the design of efficient catalyst search,so these work have become the focus of the current scientists.Since the discovery of two-dimensional layered materials like graphene,the research on two-dimensional layered materials has gradually provided us with the answer to break through the research on efficient catalysts.Due to the high specific surface area and excellent optical and electrical properties caused by the structure of such two-dimensional layered materials,such materials have excellent activity in the field of catalysis.In the few decades with the continuous evolution of computer science and the continuous consummate of the related algorithm software,people can not only rely on the experiment,but also use the method of simulation to large-scale screening suitable potential material,composite,and the appropriate modification,and simulate its ground state properties in this materials of various catalytic reaction process,so as to select the appropriate composite two-dimensional material.It also provides theoretical basis and prediction for the possibility of experiment and mass production.At present,the catalyst for efficient nitrogen reduction of electricity has a lot of progress,however,part of the performance of catalyst is still poor,affected the electrocatalysis NRR practical application,at the same time,the existing research in a large number of experiments and calculation based on high-throughput screening good catalyst which need the high cost,so we not only hope to find a kind of catalytic material with good effect,At the same time,it also hopes to use the existing big data high-throughput screening to reduce computational and experimental costs.In this paper,some two-dimensional layered catalytic materials have been designed by means of computational simulation.N vacancies have been created on the surface of two-dimensional layered W2N3,and a series of metal clusters have been loaded.The specific process of such composite materials in nitrogen reduction reaction(NRR)has been simulated,revealing some potential applications in the field of electrocatalysis.The main contents are:1.In nitrogen’s electrocatalytic reaction,nitrogen is chemically inert in its normal state,it is difficult to open the triple bond of nitrogen atoms,resulting in the subsequent H addition step very difficult.Therefore,suitable catalysts with high selectivity and high activity should be sought to promote the occurrence of NRR electrochemical catalytic reaction.Transition metal nitrides(TMN),as a relatively new two-dimensional material in recent years,are promising catalysts for NRR electrocatalytic reactions due to their excellent conductivity and high hardness as well as the properties of twodimensional materials.And clusters materials because of its special size effect with abnormal redox effect,therefore,in order to find an excellent catalytic properties of two-dimensional metal tungsten nitride composites and metal clusters,we preliminary screening of three metal clusters combined by same elements in the fourth cycle embedded in the two-dimensional metal nitrides W2N3 system,and calculate the reaction energy barrier for each system.It is found that V-Ni-Cu@NV-W2N3 has the best catalytic activity,and its rate-determining energy barrier is 0.05 eV.These ratedetermining energy barrier is lower than the noble metal catalysts that are widely studied now,that is,catalysts with stronger catalytic performance than Ru and other noble metals and their derivatives.2.In the calculation of many literatures,the cluster system composed of the same elements has been thoroughly studied,while the cluster system composed of different elements has been rarely studied.The reason may be that there are many permutations and combinations,and the amount of data is large,so more computing power is needed.In this paper,the fourth period transition metals such as Ti,V,Mn,Fe,Co,Ni,Cu,Zn were selected to permutation and combination to load heteronuclear metal clusters at the N vacancy of W2N3 two-dimensional material.The nitrogen reduction catalytic performance of these systems was calculated and evaluated as in part 1.Finally,in Density of States(DOS)analysis,the impact of spin polarization on nitrogen adsorption was demonstrated.Crystal Orbital Hamiltonian Population(COHP)explains the mutual effect between cluster metals and N2.which further proves the activation effect of these systems on nitrogen.3.With the rapid development of computer technology,people are not only simply calculating the catalytic performance of individual systems under the influence of such dividends.With the introduction and gradual realization of the concept of highthroughput computing,more and more kinds of catalysts are calculated,and the related performance data are more and more specific.Thus a descriptor or a set of formulae consisting of basic physical parameters was gradually formed.It can help reduce calculation and experiment,and only a simple physical quantity is used to describe the catalytic effect of the system.In this paper,combined with the large amount of data calculated above and the electronic structure model analyzed in Chapter 2,we continue to try to fit,and finally find three descriptors that can describe the catalytic performance of nitrogen linearly.This study provides theoretical guidance for the composite structure design of transition group metal nitrous compounds and clusters.