Ensemble averaged structure-function relationship for nanocrystals: effective superparamagnetic Fe clusters with catalytically active Pt skin

• Published in: Nanoscale 2017-10, Vol.9 (4), p.1555-15514
• Main Authors: Petkov, Valeri, Prasai, Binay, Shastri, Sarvjit, Park, Hyun-Uk, Kwon, Young-Uk, Skumryev, Vassil
• Format: Article
• Language: English
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; NANOSCIENCE AND NANOTECHNOLOGY
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c7nr05768g

Practical applications require the production and usage of metallic nanocrystals (NCs) in large ensembles. Besides, due to their cluster−bulk solid duality, metallic NCs exhibit a large degree of structural diversity. This poses the question as to what atomic-scale basis is to be used when the structure-function relationship for metallic NCs is to be quantified precisely. We address the question by studying bi-functional Fe core−Pt skin type NCs optimized for practical applications. In particular, the cluster-like Fe core and skin-like Pt surface of the NCs exhibit superparamagnetic properties and a superb catalytic activity for the oxygen reduction reaction, respectively. We determine the atomic-scale structure of the NCs by non-traditional resonant high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Using the experimental structure data we explain the observed magnetic and catalytic behavior of the NCs in a quantitative manner. Thus we demonstrate that NC ensemble-averaged 3D positions of atoms obtained by advanced X-ray scattering techniques are a very proper basis for not only establishing but also quantifying the structure-function relationship for the increasingly complex metallic NCs explored for practical applications. Ensemble-averaged 3D positions of atoms are a very proper basis for not only establishing but also quantifying the structure-function relationship for nanocrystals.