Unexpected compositional and structural modification of CoPt 3 nanoparticles by extensive surface purification

MIZRAHI, MARTÍN D.; KRYLOVA, GALYNA; GIOVANETTI, LISANDRO J.; RAMALLO-LÓPEZ, JOSÉ M.; LIU, YUZI; SHEVCHENKO, ELENA V.; REQUEJO, FÉLIX G.

Nanoscale

Royal Society of Chemistry

Lugar: Londres; Año: 2017 vol. 10 p. 6382 - 6392

2040-3364

We combined synchrotron small angle X-ray scattering, X-ray fluorescence and extended X-ray absorption fine structure spectroscopy to probe the structure of chemically synthesized CoPt3 nanoparticles (NPs) after ligand removal via the commonly accepted solvent/nonsolvent approach. We showed that the improved catalytic activity of extensively purified NPs could not be explained only in terms of a ?cleaner? surface. We found that extensive surface purification results in the substantial leaching of the Co atoms from the chemically synthesized CoPt3 NPs transforming them into CoPt3/Pt core/shell structures with an unexpectedly thick (∼0.5 nm) Pt shell. We indicated that the improved catalytic activity of extensively purified NPs in octyne hydrogenation reaction can be explained by the formation of CoPt3/Pt core/shell structures. Also, we demonstrated that drastic compositional and structural transformation of water transferred CoPt3 NPs was rather a result of extensive removal of native ligands via a solvent/nonsolvent approach than leaching of cobalt atoms in aqueous media. We expect that these findings can be relevant to other transition metal based multicomponent NPs.