Economizing on Precious Metals in Three-Way Catalysts: Thermally Stable and Highly Active Single-Atom Rhodium on Ceria for NO Abatement under Dry and Industrially Relevant Conditions*

Konstantin Khivantsev; Carlos Garcia Vargas; Jinshu Tian; Libor Kovarik; Nicholas R Jaegers; Janos Szanyi; Yong Wang

doi:10.1002/anie.202010815

Economizing on Precious Metals in Three-Way Catalysts: Thermally Stable and Highly Active Single-Atom Rhodium on Ceria for NO Abatement under Dry and Industrially Relevant Conditions*

Angew Chem Int Ed Engl. 2021 Jan 4;60(1):391-398. doi: 10.1002/anie.202010815. Epub 2020 Oct 28.

Authors

Konstantin Khivantsev¹, Carlos Garcia Vargas^{1

2}, Jinshu Tian¹, Libor Kovarik¹, Nicholas R Jaegers^{1

2}, Janos Szanyi¹, Yong Wang^{1

2}

Affiliations

¹ Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.
² Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA, 99163, USA.

PMID: 32881353
DOI: 10.1002/anie.202010815

Abstract

We show for the first time that atomically dispersed Rh cations on ceria, prepared by a high-temperature atom-trapping synthesis, are the active species for the (CO+NO) reaction. This provides a direct link with the organometallic homogeneous Rh^I complexes capable of catalyzing the dry (CO+NO) reaction. The thermally stable Rh cations in 0.1 wt % Rh₁ /CeO₂ achieve full NO conversion with a turn-over-frequency (TOF) of around 330 h^-1 per Rh atom at 120 °C. Under dry conditions, the main product above 100 °C is N₂ with N₂ O being the minor product. The presence of water promotes low-temperature activity of 0.1 wt % Rh₁ /CeO₂ . In the wet stream, ammonia and nitrogen are the main products above 120 °C. The uniformity of Rh ions on the support, allows us to detect the intermediates of (CO+NO) reaction via IR measurements on Rh cations on zeolite and ceria. We also show that NH₃ formation correlates with the water gas shift (WGS) activity of the material and detect the formation of Rh hydride species spectroscopically.

Keywords: ceria; nitric oxide; rhodium; single atom; three-way catalyst.

Abstract

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