(509bv) A General Nanocasting Encapsulation Strategy Promotes High-Temperature Stability of Metal Catalysts.

Stable catalysts are essential to address long-term energy and environmental issues. Strict regulations in the field of exhaust emission control require catalysts to maintain high reaction rates under harsh conditions. Supported noble metals have superior catalytic combustion activity, but deactivate via sintering during prolonged use in a high temperature oxidizing environment. One strategy to prevent metal nanoparticles (NPs) from sintering is to encapsulate them within metal oxides. The encapsulated NPs, however, are less active than their supported counterparts due to the blockage of the active sites by the oxide framework. Therefore, improved stability is achieved by sacrificing catalytic activity. In this talk, I will describe a general strategy to prepare stable alumina-platinum catalysts using a nanocasting strategy, where a polymer template is infiltrated with alumina precursors to yield uniform metal NPs embedded inside the alumina framework. These catalysts maintain their activity for hydrocarbon combustion after hydrothermal aging at 800 °C, while overcoming the activity-stability trade-off and displaying the high activity of a conventional Pt/Al₂O₃ catalyst. By extending the nanocasting approach to palladium-platinum (PdPt) bimetallic NPs encapsulated within alumina, we demonstrate that these materials maintain their activity even after the hydrothermal treatment at 1100°C. This modular nanocasting approach, where each component of an encapsulated catalyst is optimized independently, can be further extended to other metal nanoparticles and metal oxide supports.