Tailoring the Local Environment of Pt in Single-Atom Pt1/CeO2 Catalysts for Robust Low-Temperature CO Oxidation
Dong Jiang, Washington State University
A major challenge for automotive catalysts is attaining high reactivity while simultaneously demonstrating high thermal stability. Single-atom catalysts (SACs) have received increasing research interest for achieving maximum atom efficiency and unique reactivity. Single-atom Pt1/CeO2 synthesized by atom trapping (AT, 800 oC in the air) shows excellent thermal stability, however, it is inactive for CO oxidation at low temperatures due to over-stabilization of Pt2+ in a highly symmetric square-planar Pt1O4 coordination. Reductive activation of Pt SACs forming Pt clusters/nanoparticles (NPs) results in enhanced activities, however, these clusters/NPs are easily oxidized leading to drastic activity loss.
Here we show by tailoring the local environment of isolated Pt2+ on CeO2 via thermal-shock (TS) synthesis, it is possible to achieve high reactivity as well as high thermal stability. Ultrafast (~ 500 ms) shockwaves (> 1200 oC) in an inert atmosphere induce surface reconstruction of CeO2, allowing the formation of Pt single atoms in an asymmetric Pt1O4 configuration. Originating from this unique coordination, isolated Pt1δ+ in a partially reduced state (Pt1O4-x) is dynamically formed during CO oxidation, resulting in an exceptional low-temperature performance. The CO oxidation reactivity on the Pt1/CeO2_TS catalyst is retained under oxidizing conditions, unlike metallic Pt clusters/NPs which lose the activity.