A collaborative diffusion mechanism of multiple atoms during Cu-Ag bimetal surface reconstruction.

The reconstruction of bimetals under reaction conditions is critical for precisely controlling the catalytic performance of bimetallic catalysts. The surface diffusion mechanisms of Cu@Ag nanoparticles before and after CO adsorption were studied in this work. The diffusion patterns with the lowest energy barrier were determined by using ab initio molecular dynamics and meta-dynamics simulations. The effects of nanoparticle size, surface species and CO adsorption were taken into account. We present a mechanism of multiple atom collaborative diffusion during Cu@Ag bimetal reconstruction: surface atoms diffuse outward to form adatoms first, with nearby atoms occupying the original position of the outward diffused atom, and the outward diffusion can accelerate the inward diffusion of nearby surface atoms. The surface diffusion mechanisms of Cu@Ag under a CO atmosphere are different from those of Pd@Au that we previously presented, due to the different diffusion abilities of metal atoms. Our study provides a potential strategy to control the beginning of reconstruction to change the stability of bimetals under reaction conditions.