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 WOx and MoOx 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 WOx and MoOx 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 gZn−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.