Tailoring lattice strain in ultra-fine high-entropy alloys for active and stable methanol oxidation

High-entropy alloys (HEAs) have been widely studied due to their unconventional compositions and unique physicochemical properties for various applications. Herein, for the first time, we propose a surface strain strategy to tune the electrocatalytic activity of HEAs for methanol oxidation reaction (MOR). High-resolution aberration-corrected scanning transmission electron microscopy (STEM) and elemental mapping demonstrate both uniform atomic dispersion and the formation of a face-centered cubic (FCC) crystalline structure in PtFeCoNiCu HEAs. The HEAs obtained by heat treatment at 700°C (HEA-700) exhibit 0.94% compressive strain compared with that obtained at 400°C (HEA-400). As expected, the specific activity and mass activity of HEA-700 is higher than that of HEA-400 and most of the state-of-the-art catalysts. The enhanced MOR activity can be attributed to a shorter Pt-Pt bond distance in HEA-700 resulting from compressive strain. The nonprecious metal atoms in the core could generate compressive strain and down shift d-band centers via electron transfer to surface Pt layer. This work presents a new perspective for the design of high-performance HEAs electrocatalysts.