The modern automobile uses catalytic converters oxidize dangerous byproducts of combustion and convert them into less dangerous chemicals. Catalytic converts use a platinum based catalyst on an alumina support to achieve this oxidation. After prolonged usage or aging, Ostwald ripening allows the small platinum nanoparticles in the catalyst to sinter together, forming large macroparticles. This process lowers the overall surface area of platinum available, decreasing the total amount of catalytic activity. Ceria, a crystalline oxide forming highly ordered structures, has been shown to stabilize platinum nanoparticles and inhibit sintering. Unfortunately, ceria itself loses its structure after prolonged exposure to heat, limiting its ability to stabilize platinum.
In this research, alumina was tested as a potential support for ceria and its effectiveness for stabilizing aged ceria measured. In addition, the effect of higher ceria loadings on ceria nanoparticle size was observed, as well as preliminary testing to determine the effectiveness of ceria on alumina to stabilize platinum particles. The ceria/alumina supports were analyzed through the use of various characterization techniques. SEM/EDS imaging revealed topographical information about the support structure and measured particle sizes and distribution of the ceria. BET analysis measured the specific surface area of the ceria/alumina support, and XRD measurements provided information about particles sizes.
Results from this study showed that alumina was particularly effective at stabilizing ceria in nanoparticles. Higher loadings of ceria on the alumina resulted in lower specific surface areas and slightly larger particles; however, the alumina was still able to maintain a high degree of dispersion and stability of the ceria nanoparticles. Ceria/alumina supports were found to stabilize platinum nanoparticles at a higher level than just platinum, with a higher degree of dispersion of platinum nanoparticles after aging. Future work will investigate the effect of higher loadings of platinum on ceria/alumina supports, so as to determine the maximum supportable amount platinum in nanoparticle form. This will allow for the creation of longer lasting and more efficiently utilized catalytic converters.
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