Tailoring The Structures,Electronic,Magnetic And Catalytic Properties For O₂ And H₂O Of Pd_13-nNi_n@Pt₄₂ Nanoparticles By Ni Introduction

The tri-metallic nanoparticles have been attracted many attentions and investigations because tri-metallic nanoparticles have special structures,magnetic and catalytic properties.The structures,electronic,magnetic properties of Pd_13-nNi_n@Pt₄₂?n=0?13?tri-metallic nanoparticles,O₂ and H₂O adsorption and dissociation properties of Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?tri-metallic nanoparticles have been studied by the density functional theory.In addition,the main conclusions are as the follows aspects:1:In order to find the energetically favourable structures of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles,the isomers of every conformations are studied.The excess energy monotonically decreases with the number of Ni atoms increasing,indicating that the addition of Ni atoms can enhance the stability of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles.In addition,the change of excess energy,CNpd-Ni and Ni-Ni bond of Pd_13-nNi_n@Pt₄₂?n=0-13?nanoparticles as a function of Ni atoms are analysed,it is found that the structure which has larger CNpd-Ni and the more number of Ni-Ni have lower excess energy.Thus,the structure stability strongly depends on the CNpd-Ni and the number of Ni-Ni bond.2:With the number of Ni atoms increasing,the more charges transfer from the core Pd and Ni atoms to the shell Pt atoms.It is found that the average bond length of Pt-Pt and average Bader charge of Pt atoms change linearly with the d-band center of Pt atoms,and the linear correlation coefficient is as high as 0.98 and 0.99,respectively.This phenomenon indicates that the structures property have an influence on the electronc property of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles.3:With the number of Ni atoms increasing,the total magnetic moment of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles is increased and obtained the maximum in Pd1Ni12@Pt42?21.21 ?B?nanoparticle.In addition,with the number of Ni atoms increasing,the change tendency of total magnetic moment of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles is consistent with the average Bader charge and d-band center of Ni atoms,except for Pd11Ni2@Pt42,Pd11Ni2@Pt42 and Pd8Ni5@Pt42 nanoparticles.The change of the electronic property has an effect on the total magnetic moment of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles.Thus,it can conclude that the addition of Ni atoms play an important role in the electronic properties and total magnetic properties of Pd_13-nNi_n@Pt₄₂?n=0?13?nanoparticles.4:The adsorption of O₂ on B1 site is favorable in the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?nanoparticles,while the adsorption of O atom on the H1 site is preferred.Moreover,the adsorption energy of O₂ on the B1 site is stronger than that of B2 site.The similar characteristic can be seen that the adsorption energy of O atoms on the H1 site is stronger than that on the H2 site.The characteristics are originated from the effect of coordination number.Moreover,there is an overall trend that the adsorption of O₂ and O atom becomes stronger as d-band center of Pt close to the Fermi level.Moreover,the relationship between adsorption energy and the d-band center is consistent with d-band theory.5:In order to search for the reaction pathway of O₂ dissociation on the nanoparticles,the most stable adsorption nanoparticles structures Pd13?Pt42-B1,Pd12Ni1@Pt42-B1,Pd1Ni12?Pt42-B1,and Ni13?Pt42-B1 are treated as the initial states.The final states are chosen that one O atom locates at the V1 sites and another O atom locates at the B1 sites.Moreover,the negative reaction energy indicates that the reaction of the O₂ dissociation on the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?is exothermic and the energy barrier of the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?is 0.436,0.455,0.586 and 0.221 eV.Furthermore,the Ni13@Pt42 with the lowest energy barrier 0.221 eV yields the maximum rate constant.Thus,the Ni13@Pt42 is the most active catalyst among all the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?nanoparticles consider this work.6:As for H₂O adsorption on Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?nanoparticles,the calculations show that the two stable configurations are both at V1 and V2 sites on the Pd13@Pt42,Pd,2Ni1@Pt42 and Pd1Ni12@Pt42 nanoparticles,and only one stable configuration is V1 on the Ni13@Pt42 nanoparticle.The B1 site is the most stable site for OH adsorbed on the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?nanoparticles.The V2 site is the most stable adsorption site for H adsorbed on Pd13@Pt42 and Pd1Ni,2@Pt42,and B1 and B2 sites are the most stable adsorption site on Pd12Ni1@Pt42 and Ni13@Pt42nanoparticles,respectively.The influence of the coordination number and d-band center of Pt on the adsorption property of OH are mainly discussed.In addition,the adsorption energy of B1 site stronger than that of B2 site.The characteristic is originated from the effect of coordination number.Moreover,the linear coefficient between adsorption energy of OH and d-band center of Pt is as high as 0.99.The adsorption of OH-B2 becomes stronger as d-band center close to the Fermi-level,which is consistent with the d-band theory.7:In order to search for the minimum reaction pathway of H₂O dissociation on the nanoparticles,H₂O dissociation on the V1 of the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?and V2 site of the Pd_13-nNi_n@Pt₄₂?n=0,1,and 12?are taken into account here.Moreover,the stable adsorption structures of Pd13@Pt42,Pd12Ni1@Pt42 and Pd1Ni12@Pt42 on the V1 and V2 sites and Ni13@Pt42 on the V1 site are treated as the initial states.In addition,for the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and 13?nanoparticles catalysts,the H₂O dissociation reaction activity follows the order of Ni13@Pt42>Pd13@Pt42>Pd12Ni1@Pt42>Pd1Ni12@Pt42,illustrating that the Ni13@Pt42 is the strongest catalytic activity for H₂O dissociation reaction among of the Pd_13-nNi_n@Pt₄₂?n=0,1,12,and13?nanoparticles catalysts.8:The relationship among the adsorption energies of H20,energy barriers and reaction energies of H₂O dissociation on the V1 and V2 sites of the Pd_13-nNi_n@Pt₄₂?n=0,1,and 12?nanoparticles are analysed.Compared with the H₂O adsorption energies on the Pd_13-nNi_n@Pt₄₂?n=0,1,and 12?,the weaker adsorption is corresponding to the smaller energy barrier are observed.i.e.H₂O dissociation energy barriers on the V1 and V2 site of the Pd13@Pt42 are 1.280 and 0.691 eV,and the corresponding adsorption energies on the V1 and V2 are-0.774 and-0.716 eV,respectively.Furthermore,the smaller energy barriers and the smaller reaction energies on the Pd_13-nNi_n@Pt₄₂?n=0,1,and 12?nanoparticles.And the relationship between the energy barrier and reaction energy is similar to the Br???nsted-Evans-Polanyi relationships.