Structure–property–activity correlations of Pt-bimetallic nanoparticles: A theoretical study

A novel modeling approach based on FEFF8 calculations is developed to study the relationships between the atomic structure, electronic property, and oxygen reduction reaction (ORR) activity of Pt3M nanoparticles (NPs) in combination with experimental results. We have developed a representative cluster model of Pt3M (M = Cr, Mn, Fe, Co, Ni) NPs, namely Pt19M6, based on experimental X-ray absorption spectroscopy (XAS) data, and demonstrated that the calculated Pt surface d-band center ɛd can be directly related to the ORR catalytic enhancement trends exhibited by Pt3M NPs in cathode catalysts. The correlations between ɛd and cluster morphology parameters such as the PtPt bond distance dPtPt (strain effects), the PtM bond distance dPtM (interlayer ligand effects), and the choice of specific element M (pure ligand effects) are established. The results show that strain effects play a dominant role in downshifting ɛd for late 3d elements, and ligand (pure ligand plus interlayer strain) effects can either upshift or downshift ɛd relative to Pt depending on the near-surface morphology. The implications of the complex nature of ligand effects are discussed. This modeling approach complements the XAS technique in understanding structure–property–activity relationships of PtM NPs, and the understanding established here can be used to provide a fundamental basis for the improvement of existing cathode catalysts.

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