Surface Phase Stability of PdAg Nanoalloys and Its Relevance to Atomic Charge in Oxidizing Atmospheres
The oxidation and segregation of nanoalloys can lead to unique electrocatalytic performance in heteroge-neous catalysis.The early stage of oxidation on Pd6@Ag32 and Ag6@Pd32 core-shell nanoalloys was calculated by the sur-face phase stability diagrams using a first-principles atomistic thermodynamics method in oxidizing atmospheres.Ag38 nanoparticle with ΔμO=-0.95 eV is more stable than Pd38 nanoparticle with ΔμO=-1.3 eV.Unexpectedly,Pd6@Ag32 core-shell nanoalloy with ΔμO=-0.9 eV exhibits better surface phase stability than Ag38 nanoparticle but Pd-segregat-ed Pd6@Ag32 nanoalloys have lower stability than Ag38 nanoparticle,and Ag6@Pd32 core-shell nanoalloy with ΔμO=-1.5 eV displays lower surface phase stability than Pd38 nanoparticle but Ag-segregated Ag6@Pd32 nanoalloys show bet-ter surface phase stability than Pd38 nanoparticle.Surface-segregated Pd6@Ag32 and Ag6@Pd32 core-shell nanoalloys with more surface Ag atoms tend to possess the higher surface phase stability.The order of surface phase stability fol-lows the same trend of atomic charges,that is,the more negative charges corresponding to the lower surface phase sta-bility.The results can provide useful information for designing PdAg-based catalyst materials with appropriate surface phase stability towards fuel cells.
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