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

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) NWs with the thinnest Pt shell exhibit exceptional catalytic behaviors by achieving a mass activity of 4.26 A mg (13.91 A mg ) at 0.9 V, with < 30% decay after 20 000 cycles, overweighing most reported Pt/Pd-based ORR catalysts. The corresponding H-O anion-exchange-membrane fuel cell device delivers a very high peak power density of 1.64 W cm, with an impressive Pt utilization up to 11.71 W mg .