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Aerosol Catalysis: the Influence of Particle Structure on the Catalytic Activity of Platinum‐Nanoparticle Agglomerates
Author(s) -
Seipenbusch Martin,
Binnig Joachim,
Heim Michael,
Weber Alfred P.,
Kasper Gerhard
Publication year - 2001
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(20011219)84:12<3686::aid-hlca3686>3.0.co;2-0
Subject(s) - agglomerate , chemistry , sticking probability , nanoparticle , adsorption , catalysis , platinum , platinum nanoparticles , particle (ecology) , chemical physics , desorption , aerosol , particle size , molecule , chemical engineering , monte carlo method , nanotechnology , materials science , organic chemistry , oceanography , statistics , mathematics , geology , engineering
The structure of nanoparticle agglomerates can have substantial influence on their catalytic activity, as shown here for the oxidation of hydrogen on platinum nanoparticles. The structure of aerosol agglomerates was varied by thermally induced rearrangement of the so‐called primary particles, which were ca. 5 nm in size. In this way, the fraction of outer surface, which is directly accessible for molecules from the gas phase, was varied from a very open agglomerate structure to massive spheres. A Monte‐Carlo (MC) simulation of the surface phenomena was carried out parallel to the experiments, taking into account models for reactions including adsorption, surface diffusion, and desorption. Comparison of the experimental results with these MC simulations indicated that, for gas‐borne nanoparticles, special features appear. For instance, the time scales of experiments and simulations are not identical. This discrepancy can be explained by altered adsorption kinetics on the nanoparticles compared to the kinetics on bulk surfaces, which was introduced into the MC simulation. The assumption of a lower sticking probability for molecules impinging from the gas phase as proposed before in other investigations leads to a shift in the time scale of the MC simulation as well as an increased sticking probability for O‐atoms relative to the H‐atom sticking probability. In addition, the surface‐normalized catalytic activity, given by the turn‐over rate ( TOR ), is higher for 5‐nm than for 50‐nm particles. Thus, the combination of experiments and simulation may be a useful tool to gain deeper insight into the influence of the properties of catalyst particles on the catalytic activity, whereby the simulation covers the subsecond time range, which is hardly accessible by experimentation.