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*.

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 RhI 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.