As more efficient combustion engines are developed for transportation, it is expected that less heat will be wasted in the exhaust, leading to lower exhaust temperatures. Hence DOE has set a goal of achieving 90% conversion of target pollutants by 150 °C . To meet exhaust emission standards, it is necessary to develop catalysts that provide light off at lower temperatures than the current generation of catalysts (which become active at ~200 °C). The new targets cannot be achieved simply by increasing the loading of noble metals. One way to achieve higher reactivity at low temperatures is by control of the crystallite size of the platinum group metal (PGM) nanoparticles . Smaller particles and sub-nanometer clusters show higher reactivity, and in the limit, we can envision single atom catalysts, which provide the highest atom efficiency to reduce noble metal usage, since every atom is involved in the catalytic cycle. The challenge is to make these single atom and sub-nm structures durable so they can survive high temperature aging protocols and demonstrate performance under realistic conditions. This presentation will highlight our approach to enhance the reactivity and thermal durability of emissions control catalysts using single atom catalysts (SA
Figure 1 a) 1wt% Pt/La-Al2O3 fresh and (b) after aging in flowing air at 800 °C for 10h; (c) CO oxidation activity of the fresh and aged 1 wt% Pt/La-alumina and when polyhedral ceria was physically mixed before aging; (d) AC-STEM image showing atomically dis-persed Pt in the physically mixed ceria; (e) illustration of the process of atom trapping that helps preserve the atomic dispersion of Pt.
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