Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 48: Nanoparticles and Composite Materials II
CPP 48.10: Vortrag
Freitag, 18. März 2011, 12:45–13:00, ZEU 114
(contribution withdrawn) Effective rate constants for nanostructured heterogeneous catalysts — •Shaun Hendy1,2, Nat Lund2, and Nicola Gaston1,2 — 1Industrial Research Ltd, Lower Hutt 5010, New Zealand — 2MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand
There is currently a high level of interest in the use of nanoparticles for catalysis. With precious metal catalysts such as platinum and palladium in high demand, the use of these materials in nanoparticle form can also substantially reduce the cost of the catalyst through the exposure of more surface area for the same volume of material. When reactants are plentiful, the effective activity of a nanoparticulate catalyst will increase with its surface area, assuming that its shape is held constant and ignoring the effect of corners and edges. However, under diffusion-limited conditions, high surface area and a high density of active sites may bring diminishing returns as sites consume reactant faster than it arrives. Here we apply a mathematical homogenisation approach to derive simple expressions for the effective reactivity of a nanostructured catalyst under diffusion limited conditions that relate the intrinsic rate constants of the surfaces presented by the catalyst to an effective rate constant. When highly active catalytic sites, such as step edges or other defects are present, we show that distinct limiting cases emerge depending on the degree of overlap of the reactant depletion zone about each site. We discuss implications for the optimal design of nanoparticle catalysts.