Orchestrating dual adsorption sites and unravelling Ce-Mn interaction and reaction mechanisms for efficient NH3-SCR

Abstract

Mechanism insight is suggested to be one of the most challenging issues in selective catalytic reduction of NO with NH3 (NH3-SCR), and the development of efficient NH3-SCR catalysts for industrial application needs a deep understanding of the catalytically active sites, reaction pathways and rate-determining steps. Herein, we study the NH3-SCR reaction mechanism on CeMn oxide catalyst. Mn3+ ions enter the CeO2 lattice to generate a Mn-O-Ce structure with a strong interaction, and Ce can synergize Mn species to orchestrate co-adsorption and accelerate the reaction rate. Theoretical studies verify that Ce and Mn sites act as double adsorption sites for NH3 and NOx, respectively. The proposed two reaction pathways including NH3 with NO and NH3 with NO2 may occur simultaneously owing to the same rate-determining step and the similar energy barriers. More interesting, the simulation results suggest that oxygen vacancies can automatically generate and supplement during the NH3-SCR reaction. This present work highlights the importance of elaborately modulating the double adsorption sites for NH3 and NOx and proposes the possible reaction mechanisms.