Identification of Ru/Ceria Among Single Atom Ceria Catalysts as a Stable and Superior Material for Abatement of Diesel and Gasoline Engine Pollutants

23 July 2020, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Atomically dispersed transition metals (Ru, Pd and Pt) have been prepared on CeO2 and evaluated for NOx/CO abatement applications for diesel and gasoline engines, such as low temperature passive NOx adsorption (PNA), NO and CO oxidation, and three-way-catalysis (TWC). 0.5 wt% Ru/CeO2 catalyst (Ru is ~27 and ~7 times cheaper than Rh and Pd) shows remarkable PNA performance, better than 1 wt% Pd/Zeolite: it achieves 100% removal of NOx during vehicle cold start. FTIR measurements reveal the formation of stable Ru(NO) complexes as well spill-over of NO to CeO2 surface via the Ru-O-Ce shuttle, explaining high NO storage. Notably, Ru/ceria survives hydrothermal aging at 750 ⁰C without loss of PNA capacity. It is also a robust NO oxidation catalyst, considerably more active than Pt or Pd/CeO2. Expanding the repertoire of Ru/CeO2 catalytic applications, we further find 0.1 and 0.5 wt% Ru/CeO2 to be excellent TWC catalysts, rivaling best single-atom Rh supported materials. Our study pushes the frontier of precious metal atom economy for environmental catalysis from uber expensive Rh/Pd/Pt to more sustainable cheaper Ru and highlights the utility of single-atom catalysts for industrially relevant applications.

Keywords

diesel and gasoline engine pollution abatement
low temperature passive NOx adsorber
three way catalyst
NO oxidation catalyst
CO oxidation catalyst
single atom heterogeneous ceria catalsysts
palladium platinum ruthenium Pd Pt Ru on ceria CeO2
Ruthenium ceria as a superior catalyst

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