Defect-Engineered Perovskites: Atomic Scale Nature of A-Site Vacancy-Stabilized Catalytically Active Phase.

Area of Science:

• Materials Science
• Catalysis
• Surface Science

Background:

• Perovskite oxides are crucial catalysts for environmental applications.
• Controlling defects in perovskites is key to enhancing catalytic performance.
• A-site deficiency in perovskites influences their structural and electronic properties.

Purpose of the Study:

• To investigate the atomic-scale structure and catalytic function of A-site-deficient perovskite La_0.7Fe_0.7Mn_0.3O₃.
• To understand the role of defects in NO reduction by CO.
• To establish a structure-property relationship for defect engineering in perovskites.

Main Methods:

• Aberration-corrected electron microscopy and spectroscopy.
• In situ surface characterization.
• Catalytic measurements (NO reduction by CO).

Main Results:

• Identified a highly A-site-deficient layer (2-3 unit cells thick) at the surfaces and interfaces.
• Observed stabilization of catalytically active sites and formation of FeO_x nanoparticles (1-10 nm).
• Demonstrated that interfacial FeO_x nanoparticles are active sites for NO reduction via the Mars-van Krevelen mechanism.

Conclusions:

• A direct relationship exists between nanoscale A-site nonstoichiometry and redox-driven catalytic activity.
• Defect engineering offers a strategy for tailoring perovskite reactivity.
• Findings provide insights into designing efficient catalysts for environmental remediation.