Detailed mechanism of the NO + CO reaction on Rh(1 0 0) and Rh(1 1 1): A first-principles study

Abstract Through DFT calculations, the detailed mechanism of the catalytic NO + CO reaction, a prototypical system with great practical applications especially in the automobile-exhaust aftertreatment, was determined on Rh(1 0 0) and Rh(1 1 1). The elementary steps and their energy evolution were revealed. These steps include NO dissociation, N2 formation through N recombination, CO2 formation, and N2O formation, transformation, and dissociation. The reaction steps of NO2 formation and direct reaction between NO and CO were also studied, and were verified to be relatively insignificant in this reaction system. Results shed light on the atomic-level origin why Rh(1 0 0) is more active for this reaction system and more selective for the production of N2 versus N2O compared with Rh(1 1 1). Meanwhile, the preference between the two routes for N2 production, i.e., N atoms recombination and N2O as intermediate, was found to be dependent on the distribution of surface species and the interaction among them intricately. This work provides a basis for further kinetic modeling to investigate the catalytic properties on a realistic scale.