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

## TL;DR

This paper shows how specific atomic-scale defects in perovskite materials enhance catalytic activity for reducing NO with CO.

## Contribution

The study reveals how A-site vacancies in perovskites create catalytically active FeO_x nanoparticles via defect engineering.

## Key findings

- A-site-deficient layers at surfaces and interfaces stabilize FeO_x nanoparticles.
- These nanoparticles act as active sites for NO reduction via the Mars–van Krevelen mechanism.
- Defect engineering offers a new strategy to tailor catalytic reactivity.

## Abstract

Using aberration-corrected electron microscopy and spectroscopy,
we reveal the atomic scale structure and catalytic function of the
A-site-deficient perovskite La0.7Fe0.7Mn0.3O3, uncovering a heterogeneous defect landscape
that governs its activity in reducing NO by CO. We identified a layer
of La0.7–x
Fe0.7Mn0.3O3 that is highly A-site-deficient. This layer
is just two to three unit cells thick at the surfaces and the interfaces
of the perovskite particles and transitions toward the bulk into stoichiometric
LaFe0.7Mn0.3O3. These confined defect
layers stabilize catalytically active sites, enabling the formation
of FeO
x
inclusions ranging from approximately
1  nm to several nanometers in size at the surfaces. In situ
surface characterization and catalytic measurements reveal that these
interfacial FeO
x
nanoparticles serve as
active sites during the NO reduction by CO via the Mars–van
Krevelen mechanism. Our findings establish a direct relationship between
the structure and properties of nanoscale A-site nonstoichiometry
and redox-driven catalytic activity. This relationship offers a new
design strategy for tailoring reactivity through defect engineering.