Herein,we report the high De-NOx performance of the A-site defective perovskite-based Pd/La0.5Sr0.3MnO3 catalyst.The formation of the defective perovskite structure can be proved by both the increased Mn4+/Mn3+ ratio and serious lattice contraction due to cationic nonstoichiometry.It promotes the Sr doping into perovskite lattice and reduces the formation of the SrCO3 phase.Our results demonstrate that below 300 ℃ the A-site defective perovskite can be more efficiently regenerated than the SrCO3 phase as NOx storage sites due to the latter's stronger basicity,and also exhibits the higher NO oxidation ability than the A-site stoichiometric and excessive catalysts.Both factors promote the low-temperature De-NOx activity of the Pd/La0.5Sr0.3MnO3 catalyst through improving its NOx trapping effi-ciency.Nevertheless,above 300 ℃,the NOx reduction becomes the determinant of the De-NOx activity of the perovskite-based catalysts.A-site defects can weaken the interactions between perovskite and Pd,inducing activation of Pd sites by in-situ transformation from PdO to metallic Pd in the alternative lean-burn/fuel-rich atmospheric alternations,which boosts the De-NOx activity of the Pd/La0.5Sr0.3MnO3 catalyst.The Pd/La0.5Sr0.3MnO3 catalyst exhibits the high sulfur tolerance as well.These findings provide insight into optimizing the structural properties and catalytic activities of the perovskite-based catalysts via tuning formulation,and have potential to be applied for various related catalyst systems.