Oxygen Reduction Reactivity of Precisely Controlled Nanostructured Model Catalysts

Novel model catalysts to characterize the structural factors related to the activity of the oxygen reduction reaction (ORR) at the thin film electrode of electrocatalysts were proposed. Model catalysts were constructed of mesoporous carbon aerogels (CAGs) and ionomers of various molecular weights in order to estimate the effect of the nanostructure of the catalysts or catalyst layers on their ORR activity. The ORR kinetics of the Pt-deposited mesoporous CAG catalysts clearly depended on their pore sizes in the supports, and the smaller pore size resulted in a lower kinetic current for the ORR. However, the ORR kinetics even for the Pt-deposited CAG catalyst with the smallest pores (∼7 nm) was improved by the addition of an ionomer with a much lower molecular weight than Nafion, compared to that of the commercially available catalyst without rigid mesopores. These results indicated that the introduction of ionomers in the catalyst layer was a key to increasing the utility of a platinum catalyst and to develop a novel design of nanostructured catalyst layers.