Atomically Engineered Defect‐Rich Palladium Metallene for High‐Performance Alkaline Oxygen Reduction Electrocatalysis

Abstract Defect engineering is a key chemical tool to modulate the electronic structure and reactivity of nanostructured catalysts. Here, it is reported how targeted introduction of defect sites in a 2D palladium metallene nanostructure results in a highly active catalyst for the alkaline oxygen reduction reaction (ORR). A defect‐rich WO _x and MoO _x modified Pd metallene (denoted: D‐Pd M) is synthesized by a facile and scalable approach. Detailed structural analyses reveal the presence of three distinct atomic‐level defects, that are pores, concave surfaces, and surface‐anchored individual WO _x and MoO _x sites. Mechanistic studies reveal that these defects result in excellent catalytic ORR activity (half‐wave potential 0.93 V vs. RHE, mass activity 1.3 A mgPd ⁻¹ at 0.9 V vs. RHE), outperforming the commercial references Pt/C and Pd/C by factors of ≈7 and ≈4, respectively. The practical usage of the compound is demonstrated by integration into a custom‐built Zn‐air battery. At low D‐Pd M loading (26 µgPd cm ⁻² ), the system achieves high specific capacity (809 mAh g _Zn ⁻¹ ) and shows excellent discharge potential stability. This study therefore provides a blueprint for the molecular design of defect sites in 2D metallene nanostructures for advanced energy technology applications.