A catalytic reaction scheme for NO reduction by CO over Mn-terminated LaMnO3 perovskite: A DFT study

Abstract

Abstract LaMnO3 perovskite has been regarded as a promising catalyst for the selective catalytic reduction of NOx with CO. The relationship between the active sites and CO-SCR activity of LaMnO3 perovskite was investigated through density functional theory calculations. All possible reaction steps were proposed to comprehend the CO-SCR catalytic mechanism of NO on LaMnO3 catalyst. The results show that the Mn site at LaMnO3 surface is the dominant active site of NO reduction. The adsorption of reactants (NO and CO) on LaMnO3 surface is controlled by the chemisorption mechanism. N2O2* produced from NO coupling reaction is a crucial reaction intermediate of SCR reaction. N2O2* further reacts with the chemisorbed CO to form CO2 and N2O* intermediate with an activation energy barrier of 50.20\xa0kJ/mol. The activation energy barrier of NO decomposition on LaMnO3 surface is larger than that of N2O2* formation, which suggests that the bimolecular mechanism is responsible for the CO-SCR of NO over LaMnO3 catalyst. The reaction pathway of CO-SCR on LaMnO3 surface contains three steps: 2NO*\xa0→\xa0N2O2*, N2O2*\xa0+\xa0CO*\xa0→\xa0N2O*\xa0+\xa0CO2 and N2O*\xa0+\xa0CO*\xa0→\xa0N2\xa0+\xa0CO2*. The rate-limiting step of CO-SCR reaction on LaMnO3 surface is the reduction of N2O.