Exploring the dynamic evolution of lattice oxygen on exsolved-Mn2O3@SmMn2O5 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 Mn2O3/SmMn2O5 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 Mn3+ sites, induced by the interface between exsolved Mn2O3 and mullite, lead to the formation of highly active lattice oxygen adjacent to Mn3+ 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 NO2 desorption via the cooperative Mars-van Krevelen mechanism. Therefore, the Mn2O3/SmMn2O5 exhibits higher NO oxidation activity and better resistance to hydrothermal aging compared to a commercial Pt/Al2O3 catalyst

Hydrothermal synthesis and characterization of lanthanide oxalates: <i style="">In situ</i> oxalate formation from tartaric acid in presence of KI

708-713Two new three-dimensional lanthanide oxalates [Pr2(C2O4)3(H2O)4]·2H2O (1) and [Nd2(C2O4)3(H2O)4]·2H2O (2) and a two-dimensional oxalate [Pr2(C2O4)3(H2O)6]·3H2O (3) have been prepared by hydrothermal process and characterized by single crystal X-ray analysis. Compound (1) crystallizes in monoclinic crystal system with P21/c space group whereas (2) crystallizes in triclinic crystal system with Pī space group. Although Pr and Nd are twin lanthanides, they have produced different crystal structures under the same reaction conditions. Compound (3) is produced by the in situ hydrothermal degradation of tartaric acid to oxalate ions in presence of KI. In this reaction, the iodide anion instead of metal cation, acts as the reducing agent during the degradation of tartaric acid to oxalate. Thermogravimetric, elemental analysis and IR studies have also been carried out for these compounds