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

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.