Statistical Thermodynamic Analysis And Molecular Dynamics Calculation Of Pt Metal Nanoparticles

Compared with bulk materials,nanomaterials have a larger specific surface area,resulting in excellent catalytic activity,and have been widely used in energy and energy storage fields.Platinum(Pt)nanoparticles are widely used as important electrocatalysts in industrial production and commercial equipment,especially in direct methanol fuel cells,because of their ability to promote both oxidation and reduction reactions.However,two factors restrict its effective use.On the one hand,THE content of Pt in nature is extremely rare and its price is very high.On the other hand,the intermediate CO produced in methanol oxidation reaction can easily poison Pt nanoparticles and inactivate them.Therefore,it is extremely necessary and urgent to explore Pt nanoparticles catalysts with high activity.With the continuous processing of various metal nanoparticles,the research on the properties of metal nanoparticles is becoming more and more extensive.Due to the high cost,complex design and difficulty in operation,it is difficult to observe and determine the microscopic changes of the reaction and the optimal preparation conditions in the experiment.Thanks to the development of computer technology,it is possible to study the microscopic changes of materials through simulation calculation,which provides theoretical guidance for the preparation of high-performance catalysts.In this paper,the surface structural characteristics,adsorption behavior and catalytic mechanism of Pt nanoparticles were studied by combining first-principles analysis and molecular dynamics calculation,and the catalytic mechanism of Pt nanoparticles was explained theoretically.The research content and calculation results of this paper are as follows:(1)In this paper,based on molecular dynamics method and LAMMPS software,the structural characteristics and phase transformation of Pt nanoparticles were studied.Firstly,based on the structural characteristics,the influence of thermodynamic phase transition on surface structure is further explored.Secondly,the surface structure of Pt nanoparticles was subdivided into 30 layers by hierarchical calculation method,and the coordination number and the structural characteristics of active sites on the surface of Pt nanoparticles were analyzed layer by layer,providing theoretical basis for the improvement of catalytic performance of Pt nanoparticles.(2)In this paper,the influence of different sizes on the melting point of metal nanoparticles and the morphologies of the same size in the melting process were studied.It is found that there is a linear relationship between the melting point and the size of Pt nanoparticles in a certain size range,and Pt nanoparticles gradually melt from the surface to the core during the melting process.This indicates that the atomic vibration frequency of the shell is higher than that of the core,which indicates that the structural characteristics of Pt catalyst can be regulated by the phase transformation law,and provides a simulation reference for the regulation of the surface structure.(3)The oxygen reduction reaction(ORR)on strain Pt(100)surface was studied by first principles.The results show that there is a linear relationship between strain and d-band center.The adsorption energy is sensitive to pressure strain.Meanwhile,the calculation results of free energy diagram show that the compression deformation can reduce the overpotential of THE ORR reaction on Pt(100)surface.It should be noted that the OOH* scaling relationship with OH* or O* was limited to fit potential at each step.When the compressive strain reached 10%,the upper limit of OER reaction overpotential was 0.804 V.