Combined insights from DFT and microkinetics into NO reduction by CO over an LaFeO3 perovskite

Abstract

Herein, the relationship between the selective catalytic activity of CO in the reduction of NO and the active site of LaFeO₃ perovskite was established through the combination of density functional theory and microkinetic studies. A reaction network consisting of various possible elementary reactions was built to reveal the pathway of CO₂, N₂ and N₂O formation during CO-SCR on LaFeO₃. The results indicated that the Fe site was active for reactant adsorption, which followed a chemisorption mechanism. The intermediate N₂O₂-mediated path was dominant for CO-SCR. Firstly, N₂O₂* was produced via the bimolecular reaction of NO-coupling with an energy barrier of 0.26 eV. Subsequently, N₂O₂* easily reacted with the adsorbed CO molecules to form an N₂O₂CO* intermediate (N₂O₂* + CO* → N₂O₂CO* + *), which required an activation energy of 0.65 eV. Finally, the formed N₂O₂CO* intermediate was reduced by CO* to generate N₂ and CO₂ (N₂O₂CO* + CO* → 2CO₂ + N₂ + 2*) with an energy barrier of 1.22 eV. Besides, the formation and decomposition of N₂O were considered. N₂O might have been formed via N–NO disproportionation reaction (NO* + N* → N₂O + 2*) and decomposition of N₂O₂CO* (N₂O₂CO* → N₂O + CO₂ + *). Microkinetic results indicated that the conversion rate of CO and NO and the temperature showed a volcanic curve, and the N₂ selectivity reached 100% at temperatures between 200 and 420 K. Thus, this work provides a detailed description of the CO-SCR reaction mechanism and lays the foundation for the development of high-performance LaFeO₃ catalysts.