Stability, oxidation and shape evolution of PVP-capped Pd nanocrystals

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Collins, Gillian
Schmidt, Michael
McGlacken, Gerard P.
O'Dwyer, Colm
Holmes, Justin D.
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American Chemical Society
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A critical aspect in the practical applications and catalytic performance of shape-controlled nanocrystals is their stability and morphology retention under ambient conditions. Changes to the morphology of shape-controlled Pd nanocrystals capped by PVP are assessed by TEM, and surface oxidation was evaluated by X-ray photoelectron spectroscopy (XPS) over 12 months. Surface oxidation of PVP-capped Pd nanocrystals resulted in the loss of edge and corner sites and a transition to spherical morphologies. The shape stability of the nanocrystals was found to follow the trend cubic < cuboctahedra < octahedral ∼ concave cubes. For low index planes, {111} surfaces were more resistant to oxidation compared to {100} facets, correlating with the surface free energy of the nanocrystals. Cubic and cuboctahedral nanocrystals transitioned to spherical particles while octahedral nanocrystals retained their morphology. The presence of high-energy {110} facets was observed in the cubic nanocrystals which undergo surface reconstruction. The presence of surface defects may also influence the rate of the structural changes. Concave cubic nanocrystals, which possess high index facets and surface energies, were consistently found to display excellent morphology retention. The concave cubic nanocrystals displayed superior shape stability and reduced oxidation compared to cubic and cuboctahedral nanocrystals. XPS analysis further determined that PVP capping ligands on different Pd surface facets strongly influenced the morphological consistency. The stability of the concave cubes can be attributed to the stronger chemisorption of PVP capping ligands to the high index planes, making them less susceptible to oxidation.
Ligands , Morphology , Oxidation , Photoelectrons , Stability , X ray photoelectron spectroscopy , Ambient conditions , Catalytic performance , High index planes , Reduced oxidation , Spherical morphologies , Spherical particle , Surface free energy , Surface oxidations , Nanocrystals
COLLINS, G., SCHMIDT, M., MCGLACKEN, G. P., O’DWYER, C. & HOLMES, J. D. 2014. Stability, Oxidation, and Shape Evolution of PVP-Capped Pd Nanocrystals. The Journal of Physical Chemistry C, 118, 6522-6530.
© 2014 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see