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- Werdinius, C, et al.
(author)
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Nanofabrication of planar model catalysts by colloidal lithography : Pt/ceria and Pt/alumina
- 2003
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 19:2, s. 458-468
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Journal article (peer-reviewed)abstract
- We present a novel method, called colloidal lithography, to prepare well-defined model catalysts on planar supports. The method facilitates fabrication of monodisperse catalyst particles with variable, well-defined size, shape, and interparticle distance. The chemical and structural composition of the constituents (i.e., catalyst particles and support materials) maybe independently varied. Large batches of model catalysts may be made in short processing times, with the dimensions of the samples only limited by the physical dimension of available support material, the processing vacuum systems, and so forth. Here we employed 2 in. Si wafers cut into 1 x 1 cm(2) pieces as the primary lithography support, onto which the support (ceria and alumina) and active catalyst materials (Pt in this case) were deposited. A detailed chemical and structural characterization is presented of the individual steps in the fabrication process. The oxygen plasma used to remove the colloidal mask residues is shown to lead to substantial but reversible Pt oxidation. As a probe reaction, to validate the nanofabrication process, CO oxidation measurements were performed on 130 nm Pt particles on an alumina or a ceria support. The reactivity measurements are in good agreement with literature data and suggest a satisfactory performance of the colloidal lithography model catalysts.
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| 2. |
- Österlund, Lars, 1967-, et al.
(author)
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Reactivity of Pt/ceria and Pt/alumina planar model catalysts prepared by colloidal lithography
- 2003
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In: Journal of Catalysis. - 0021-9517 .- 1090-2694. ; 215:1, s. 94-107
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Journal article (peer-reviewed)abstract
- We report on the structure, chemical state, and catalytic activity of nanofabricated, planar Pt/ceria and Pt/alumina model catalysts prepared by colloidal lithography. Employing extended etching times, catalyst particles are fabricated that are much smaller than the size of the polystyrene colloidal particle mask. Using CO oxidation as a probe reaction, the influence of various pretreatments has been studied. We find that the H-2/O-2 pretreatment deteriorates the reactivity on Pt/alumina, which is accompanied by blocking of the high-temperature CO adsorption sites as seen by TPD. After prolonged reactions the Pt/ceria particles show pronounced restructuring, indicating a low-temperature, reaction-induced, strong metal-support interaction, where ceria is decorating the Pt particles. In contrast, after an identical reaction history the Pt/alumina particles become facetted. The nanofabrication approach allows us to attribute the structural changes on individual particles to the integrated, macroscopic catalytic response. (C) 2003 Elsevier Science (USA). All rights reserved.
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