Atomic Simulation Of Element Segregation And Thermal Stability Of Ni-Based Alloy Nanoparticles

The dry reforming reaction of methane（DRM）needs to be carried out at a high temperature,and the catalyst is required to have high resistance to carbon deposition and sintering.The bimetallic catalysts made of nickel and noble metals or some transition metals have good catalytic activity,economy and carbon deposition resistance,which is an ideal choice for DRM reaction catalysts.In this thesis,Ni-Rh,Ni-Pd and Fe-Ni nanoparticles were taken as the research objects.Molecular dynamics and Monte Carlo methods were used to simulate the element segregation behavior and thermal stability of Ni-based alloy nanoparticles.By analyzing the experimental data and fitting the potential parameters,the ADP potentials of the three alloys were obtained and compared with the experimental values and the calculated results of EAM potential and MEAM potential to verify the reliability of these potentials.Based on the above ADP potentials,the chemical ordering pattern,composition distribution,inducing factors of element segregation,the effect of size and temperature on surface segregation and the melting point of Ni-based alloy nanoparticles with CO and ICO structure under DRM reaction conditions are simulated.The results show that adding a small amount of Rh into Ni nanoparticles can improve the catalytic activity,carbon deposition resistance,and sintering resistance of the catalyst.Adding a small amount of Pd can improve the catalytic activity and carbon deposition resistance of the catalyst,but it will reduce its sintering resistance.The addition of Fe can improve the catalytic activity,carbon deposition resistance,and sintering resistance of the catalyst.Based on the above results,the optimal ratios of Ni-based alloy nanoparticle catalysts are Ni_0.9Rh_0.1,Ni_0.9Pd_0.1,and Fe_0.375Ni_0.625,respectively.By using numerical calculations to simulate the elemental segregation behavior and thermal stability of Ni-based alloy nanoparticles,the optimal composition of alloy nanoparticles was predicted,providing theoretical support for catalyst design in DRM reactions.It should be noted that the above conclusions were obtained through research under vacuum conditions,without considering changes in the reaction atmosphere.The change in the reaction atmosphere may cause the recombination of bimetallic nanoparticle catalysts,affecting the chemical ordering and elemental segregation of nanoparticles.The impact of these changes on catalyst performance still needs to be studied.