title: Revealing the Formation of Copper Nanoparticles from a Homogeneous Solid Precursor by Electron Microscopy.
abstract: The understanding of processes leading to the formation of nanometer-sized particles is important for tailoring of their size, shape and location. The growth mechanisms and kinetics of nanoparticles from solid precursors are, however, often poorly described. Here we employ transmission electron microscopy (TEM) to examine the formation of copper nanoparticles on a silica support during the reduction by H2 of homogeneous copper phyllosilicate platelets, as a prototype precursor for a coprecipitated catalyst. Specifically, time-lapsed TEM image series acquired of the material during the reduction process provide a direct visualization of the growth dynamics of an ensemble of individual nanoparticles and enable a quantitative evaluation of the nucleation and growth of the nanoparticles. This quantitative information is compared with kinetic models and found to be best described by a nucleation-and-growth scenario involving autocatalytic reduction of the copper phyllosilicate followed by diffusion-limited or reaction-limited growth of the copper nanoparticles. The plate-like structure of the precursor restricted the diffusion of copper and the autocatalytic reduction limited the probability for secondary nucleation. The combination of a uniform size of precursor particles and the autocatalytic reduction thus offers means to synthesize nanoparticles with well-defined sizes in large amounts. In this way, in situ observations made by electron microscopy provide mechanistic and kinetic insights into the formation of supported nanoparticles, essential for the rational design of nanomaterials.
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University , Universiteitsweg 99, 3584 CG Utrecht, Netherlands.
authors.forename: Roy
authors.initials: R
authors.lastname: van den Berg
authors.affiliation: Haldor Topsoe A/S, Haldor Topsøes Allé 1 , DK-2800 Kgs. Lyngby, Denmark.|Department of Physics, Technical University of Denmark , Fysikvej 312, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Christian F
authors.initials: CF
authors.lastname: Elkjaer
authors.affiliation: Department of Chemical Engineering, University of Liège , Allée du 6 août 3, B-4000 Liège, Belgium.
authors.forename: Cedric J
authors.initials: CJ
authors.lastname: Gommes
authors.affiliation: Department of Physics, Technical University of Denmark , Fysikvej 312, DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Ib
authors.initials: I
authors.lastname: Chorkendorff
authors.affiliation: Haldor Topsoe A/S, Haldor Topsøes Allé 1 , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Sehested
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University , Universiteitsweg 99, 3584 CG Utrecht, Netherlands.
authors.forename: Petra E
authors.initials: PE
authors.lastname: de Jongh
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University , Universiteitsweg 99, 3584 CG Utrecht, Netherlands.
authors.forename: Krijn P
authors.initials: KP
authors.lastname: de Jong
authors.affiliation: Haldor Topsoe A/S, Haldor Topsøes Allé 1 , DK-2800 Kgs. Lyngby, Denmark.
authors.forename: Stig
authors.initials: S
authors.lastname: Helveg