(366a) Self-Healing Catalysts Via Atom Trapping

The groundbreaking work by Prof. Maria Flytzani-Stephanopoulos on single atom catalysts inspired us to study ways to make single atom catalysts thermally stable. Our initial work was focused on Pt which sinters when heated in air due to formation of volatile PtO₂. Trapping the Pt ions in ceria, a process we termed atom trapping [1], allows atomically dispersed Pt to be stable at 800 °C in air, achieving the goal of creating a thermally stable single atom catalyst. However, the ability of ceria to stabilize Pt ions is limited to specific sites on the surface of the oxide support. Here we show that PdO can trap Pt ions at much higher concentrations because Pt ions can be accommodated into the PdO lattice forming a solid solution. When heated in air to 800 °C, we find that biphasic particles are formed where the oxide phase is conjoined to the metal, in apparent thermodynamic equilibrium [2]. This composite biphasic particle represents a prototypical self-healing catalyst where the Pd oxide can trap Pt ions and recycle them to the metallic phase. We will show how atom trapping is critical to understanding how Pd helps to stabilize Pt in diesel oxidation catalysts.