Coupling macro-strain and micro-strain for high-performance PtCo fuel cell catalysts

Macro-strain is introduced by synthesizing single-crystal PtCo nanodendrites, whereas acid etching introduces micro-strain to the surface. Macro-strain lowers the d -band center of Pt and improves oxygen reduction reaction (ORR), while micro-strain produces surface configuration of richer active sites, enhancing ORR activity and stability. Limited by the sluggish kinetics at the cathode of proton exchange membrane fuel cells (PEMFCs), optimizing platinum-based alloy catalysts for oxygen reduction reaction remains a key target toward industrialization. Strain engineering is widely employed to tune Pt-M catalysts, but its impact on the structure-property relationship is often interwoven with multiple factors. In this work, we propose a bi-stage strain tuning method and demonstrate it on the most common PtCo catalysts. Macro-strain is introduced by synthesizing single-crystal PtCo nanodendrites, whereas mild acid etching introduces micro-strain to the surface. The half-wave potential of as-treated catalysts reaches 0.959 V, and mass activity is up to 0.69 A mg −1 Pt . A minimal decrease of 2 mV is observed for half-wave potential after 10,000 cycles. Detailed analysis using advanced transmission electron microscopy, wide-angle X-ray scattering, etc. provides direct evidence that surface disorder at the atomic scale accounts for the enhanced activity and stability. In contrast, the simplicity of this approach allows for scaling up on Pt-M catalysts, as demonstrated on PEMFCs. The bi-stage strain tuning strategy provides a new perspective and reference for improving the activity and durability of Pt-M catalysts.