Intrinsic synergy mechanism of oxygen vacancy and Lewis acid site over LaCoO₃ for enhanced catalytic NO oxidation

Discerning intrinsic catalytic-site activity enables the rational design of high-performance perovskite-based catalysts for diesel oxidation. Herein, three representative LaCoO₃ catalysts with different surface properties were fabricated via sol-gel, coprecipitation, and hydrothermal methods (labelled as LCO-S, LCO-C, and LCO-H, respectively) to unravel the fundamental mechanisms governing NO oxidation. Characterization results reveal that metastable single-electron-trapped oxygen vacancies (VOs) can provide coordinatively unsaturated sites for O₂ absorption and produce reactive oxygen species (ROS: O₂^2– and O₂^–) via the electron transfer processes. Additionally, adjacent low-coordinated Co²⁺ Lewis acid sites preferentially adsorb and activate NO molecules through d-orbital hybridization, enabling the efficient oxidation with neighboring ROS. Impressively, the dynamic cooperation of this dual-site configuration drives LCO-S to achieve a remarkable specific reaction rate (28.9 nmol s^-1 m⁻²), which is respectively 1.4 and 7.8 times higher than that of LCO-C and LCO-H. This dual-site cooperation mechanism establishes a new paradigm for rationalizing efficient non-precious oxidation catalysts.