Synergistic engineering of A-site defects and grain boundaries in LaCoO3 for efficient catalytic oxidation of chlorobenzene and toluene.

Defect engineering has recently emerged as a pivotal strategy in the design of perovskite catalysts. Atomic disorder at grain boundaries, characterized by abundant coordinatively unsaturated atoms and oxygen vacancies, generates active sites that facilitate reactant adsorption and activation. However, the concurrent catalytic removal of toluene and chlorobenzene on perovskite catalysts, along with their mutual influence and interaction mechanisms, remains inadequately elucidated. Consequently, the rational design of LaCoO3 catalysts with controlled grain boundary structures represents a significant research challenge. In this research, we developed a one-pot, urea-modified LaCoO3 perovskite catalyst that enables in-situ regulation of lanthanum vacancies (VLa) and promotes grain boundary growth. We elucidated the fundamental relationship between grain boundary density and oxygen adsorption capacity in LaCoO3 and employed the catalyst for the simultaneous oxidation of chlorobenzene and toluene. Moderate urea modification induced La vacancies at the grain boundaries, providing a driving force for complex structural reconstruction, while the grain boundaries accommodated these vacancies and associated lattice distortions. The abundant grain boundaries facilitated the adsorption and activation of chlorobenzene, toluene, and O2, which is critical for the Mars-van Krevelen mechanism. Furthermore, these boundaries could effectively host or disperse chlorine species, thereby mitigating catalyst deactivation. As a result, LaCoO3-2U exhibited superior low-temperature activity, reducing the temperature required for 90% chlorobenzene conversion (T90) by more than 45 °C compared to the unmodified perovskite, while also accelerating the deep oxidation of chlorinated byproducts. These findings highlight the critical role of rational A-site defect engineering in the design of efficient catalysts for the abatement of chlorinated and non-chlorinated volatile organic compounds (CVOCs and VOCs).