Ultrathin and defect-rich intermetallic Pd2Sn nanosheets for efficient oxygen reduction electrocatalysis†
Atomic ordering engineering has been a promising strategy to improve the catalytic activity and stability of Pt-based alloy catalysts for the oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs). However, the synthesis of shape-controlled ordered nanocrystals, especially in a two-dimensional (2D) architecture, still remains a great challenge. Herein, 2D Pd2Sn nanosheets (NSs) with unique Pd–Sn ordering are developed as efficient ORR electrocatalysts for the first time. The ordered Pd2Sn NSs exhibit a mass activity of 2.5 A mgPd−1 at 0.9 ViR-free vs. the reversible hydrogen electrode and outstanding durability, much superior to that of their disordered counterparts, commercial Pt/C, and most of the reported Pd-based ORR catalysts. The outstanding activity and stability can be ascribed to the unique 2D defect-rich morphology, the thermodynamically stabilized intermetallic structure, and the optimized Pd–O binding due to Sn incorporation.