Experimental and DFT studies on Sr-doped LaMnO₃ catalysts for NO_x storage and reduction

Abstract

The idea of rational design of perovskite catalysts for NO x storage and reduction (NSR) starts from DFT studies on Sr-doped LaMnO 3 (001) plane models: a Mn-terminated plane (Mn-ter) has a higher activity than La-or Sr-ter planes; the number of A-site defects increases when Sr is doped on the surface; O-vacancy formation energies for both La-and Mn-ter gradually decrease with increased Sr loading, and the values for La-ter are always larger than for Mn-ter with the same Sr loading, indicating that the O-vacancy formation is facile on Mn-ter with Sr-doping. This model yields the highest reactivity for oxidation and the lowest energy barrier for O-vacancy formation. A surface tuning method for La 0.5 Sr 0.5 MnO 3 is introduced. With the exception of the promotion of surface area and pore volume, the ratio of Sr/La and the number of surface-active oxygen atoms and Mn 4+ cations exposed on the outermost layers are improved with an increased contact time between the raw materials and dilute HNO 3 . However, overtreatment leads to a less stable phase of MnO 2 with a high reducibility but significantly restrained NO x adsorption. NSR performances under lean-burn/fuel-rich cycles are measured, and the results correspond well with the NO adsorption or oxidation behaviors and DFT calculations.Catal. Sci. Technol. This journal is

Physico-chemical properties and catalytic activity of the sol-gel prepared Ce-ion doped LaMnO3 perovskites

“…Perovskite materials mostly applied for removing common exhaust pollutants including carbon monoxide, hydrocarbon, ammonia oxidation, water dissociation, and NOx, etc. 1–3 . Amongst different perovskite, Mn-containing oxide materials have been growing a considerable interest from the researchers because of the large specific external area, high thermo-chemical durability and extraordinary catalytic performance even at environmental conditions 2–9 .…”

Promotion of Oxygen Reduction with Both Amorphous and Crystalline MnOx through the Surface Engineering of La0.8Sr0.2MnO3‐δ Perovskite

“…Obviously, according to the characterizations in this research, the greater exposure of B-site transition-metal cations on the surface is the main factor for the ORR catalytic activity. It has been also noted that the surface with Mn has higher activity than those with La or Sr via the calculation with density functional theory [59]. In addition, the increased specific surface area and the mesoporous structure improve the ORR activity by providing more active sites and mass-transfer channels.…”

Perovskite-Based Catalysts as Efficient, Durable, and Economical NOx Storage and Reduction Systems

“…Some of the studies reported in Table 1 have been focused on understanding the electronic structure of perovskites [54,69,71]. Specifically, Density Functional Theory (DFT) calculations have been carried out to analyze the NO-to-NO 2 reaction on LaCoO 3 -type perovskites.…”