Sub‐Nanometer PtSn Interlayer Tuning Ligand and Strain Effects Boosts Oxygen Reduction Electrocatalysis

ABSTRACT The integration of ligand and strain effects in core/shell architectures offers a compelling avenue for boosting the catalytic efficiency of noble metals. However, conventional thin‐Pt‐shell catalysts incorporating small‐radius transition metals suffer from an over‐compressed Pt lattice, leading to limited oxygen reduction reaction (ORR) performance toward fuel cell devices. Herein, we report a class of PdSn/PtSn/Pt sandwich‐structured nanowires based on large‐radius Sn elements, taking advantage of its diffusion inclination to Pt, to construct the sub‐nanometer PtSn interlayer so as to address this trade‐off issue. We demonstrate that the intermetallic Pt‐Sn bonds with elevated covalency downshift the d‐band center of Pt through strengthened ligand effect, and the diffusion of large‐radius Sn atoms from PdSn core to Pt shell surprisingly offsets an optimally compressive strain for surface Pt. Thanks to such two‐tier tuning from PtSn interlayer, the resulting PdSn/(PtSn/Pt) 2‐3L NWs with the thinnest Pt shell exhibit exceptional catalytic behaviors by achieving a mass activity of 4.26 A mg Pt+Pd −1 (13.91 A mg Pt −1 ) at 0.9 V RHE , with < 30% decay after 20 000 cycles, overweighing most reported Pt/Pd‐based ORR catalysts. The corresponding H 2 ‐O 2 anion‐exchange‐membrane fuel cell device delivers a very high peak power density of 1.64 W cm −2 , with an impressive Pt utilization up to 11.71 W mg Pt −1 .