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

Herein, the relationship between the selective catalytic activity of CO in the reduction of NO and the active site of LaFeO 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 CO, N and NO formation during CO-SCR on LaFeO. The results indicated that the Fe site was active for reactant adsorption, which followed a chemisorption mechanism. The intermediate NO-mediated path was dominant for CO-SCR. Firstly, NO* was produced the bimolecular reaction of NO-coupling with an energy barrier of 0.26 eV. Subsequently, NO* easily reacted with the adsorbed CO molecules to form an NOCO* intermediate (NO* + CO* → NOCO* + *), which required an activation energy of 0.65 eV. Finally, the formed NOCO* intermediate was reduced by CO* to generate N and CO (NOCO* + CO* → 2CO + N + 2*) with an energy barrier of 1.22 eV. Besides, the formation and decomposition of NO were considered. NO might have been formed N-NO disproportionation reaction (NO* + N* → NO + 2*) and decomposition of NOCO* (NOCO* → NO + CO + *). Microkinetic results indicated that the conversion rate of CO and NO and the temperature showed a volcanic curve, and the N 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 LaFeO catalysts.