Exploring the dynamic evolution of lattice oxygen on exsolved-Mn 2 O 3 @SmMn 2 O 5 interfaces for NO Oxidation.

Lattice oxygen in metal oxides plays an important role in the reaction of diesel oxidation catalysts, but the atomic-level understanding of structural evolution during the catalytic process remains elusive. Here, we develop a Mn 2 O 3 /SmMn 2 O 5 catalyst using a non-stoichiometric exsolution method to explore the roles of lattice oxygen in NO oxidation. The enhanced covalency of Mn-O bond and increased electron density at Mn 3+ sites, induced by the interface between exsolved Mn 2 O 3 and mullite, lead to the formation of highly active lattice oxygen adjacent to Mn 3+ sites. Near-ambient pressure X-ray photoelectron and absorption spectroscopies show that the activated lattice oxygen enables reversible changes in Mn valence states and Mn-O bond covalency during redox cycles, reducing energy barriers for NO oxidation and promoting NO 2 desorption via the cooperative Mars-van Krevelen mechanism. Therefore, the Mn 2 O 3 /SmMn 2 O 5 exhibits higher NO oxidation activity and better resistance to hydrothermal aging compared to a commercial Pt/Al 2 O 3 catalyst.