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 ah igh-temperature atomtrapping synthesis,a re the active species for the (CO + NO) reaction. This provides ad irect 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 %R h 1 /CeO 2 achieve full NO conversion with at urnover-frequency (TOF) of around 330 h À1 per Rh atom at 120 8 8C. Underdry conditions,the main product above100 8 8Cis N 2 with N 2 Ob eing the minor product. The presence of water promotes low-temperature activity of 0.1 wt %R h 1 /CeO 2 .I n the wet stream, ammonia and nitrogen are the main products above120 8 8C. 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 NH 3 formation correlates with the water gas shift (WGS) activity of the material and detect the formation of Rh hydride species spectroscopically.

Identification of single Ru(II) ions on ceria as a highly active catalyst for abatement of NOx pollutants

“…S1). Doping ceria with these ions produces stable materials that can survive heating in air at 800 ºC in agreement with our latest findings [42]. HAADF-STEM images of Pd, Pt and Ru supported ceria materials (Fig.…”

“…To confirm the versatility of Ru/ceria materials for NOx related environmental catalysis, we now turn our attention to another challenging reaction for gasoline engines called NO reduction. TWC materials should perform catalytic removal of NOx in the presence of CO and water vapor under stoichiometric conditions [39][40][41][42]. We recently discovered that isolated Rh(I) ions on ceria can perform low temperature NO reduction by CO [42] effectively.…”

Single atom catalysis poised to transition from an academic curiosity to an industrially relevant technology

“…The promise of single-atom catalysts is to lower the requirements for platinum group metals by utilizing these metals more efficiently. This was achieved recently by Khivantsev et al at PNNL through the use of Rh at ultralow loadings (0.1 wt%) prepared via atom trapping for NO reduction 19 . In summary, recent research shows pathways for scalable synthesis of single-atom catalysts that might deliver catalysts meeting the thermal durability requirements of industry, while yielding reactivity improvements over conventional supported metal nanoparticle catalysts.…”

Elucidating the role of CO in NO storage mechanism on Pd/SSZ-13 with in situ DRIFTS

“…The global air pollution crisis poses a substantial challenge for the automotive industry to develop improved emission technologies. [1][2] Current and future regulations aim for nearly zero emissions, which requires the development of effective technologies for NOx abatement during the cold start period of a vehicle operation. Current NOx control for lean-burn diesel exhaust is achieved by either NOx storage and reduction (NSR) catalysts or selective catalytic reduction (SCR) catalysts using urea as the reducing agent.…”