Catalytic conversion of NO and CO into N2 and CO2 by rhodium–aluminum oxides in the gas phase

Abstract

The increasingly stringent emission regulations make it urgent to get a fundamental understanding on the catalytic behaviors of rhodium, the most efficient component in three-way catalysts (TWCs) to convert NO_x into N₂. Herein, the catalytic conversion of NO and CO into N₂ and CO₂ by gas-phase rhodium-aluminum oxide species (RhAlO_0–3 and RhAl₂O_1–4) was identified by mass spectrometry and quantum chemical calculations. This finding represents a significant step in the field of gas-phase catalysis, given that only elementary reactions for this conversion are commonly observed because it is extremely challenging to rupture the strong N–O bond and couple the N–N bond as well as drive the resulting product to oxidize CO. It emphasized that a polarized Rh–Al bond in gas-phase species is indispensable and the RhAlO_0,1 and RhAl₂O_1,2 species with direct Rh–Al bonding can be involved in catalytic NO reduction by CO.