Defect-engineered nonstoichiometric perovskite hosting high-activity PdO sites for enhanced hydrocarbon oxidation

Supported noble metal catalysts are central to industrial, environmental, and energy applications, yet precisely constructing active sites with optimized geometry remains a formidable challenge beyond conventional particle size control. Here, we introduce a perovskite-based surface defect engineering strategy that enables atomic-level regulation of noble metal active sites. By tailoring La stoichiometry in LaAlO₃, we engineer three distinct surface morphologies (planar, stepped, and crater-like) that serve as templates for anchoring and replicating supported PdO nanoparticles. Among these, the step-rich PdO configuration on La_0.9AlO_3-δ exhibits the highest methane oxidation activity, with a linear correlation between Pd step-site density and catalytic performance. The enhancement arises from low-coordination Pd atoms at step sites, which form stable Pd-C(CH₃) covalent bonds and facilitate C-H bond activation, the rate-determining step in methane oxidation. This work establishes a generalizable approach to precisely tailor noble metal active sites through perovskite surface engineering, providing a robust framework for the rational design of efficient and durable oxidation catalysts.