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.

A highly accurate high-dimensional neural network potential (HDNNP), trained using more than 180,000 DFT-calculated structures, is used to investigate the structure or realistic Cu-Ag bimetallic particles, as this is the dominant species during the CO₂ reduction process. The structural transition of Cu and Ag nanoparticles of increasing size, ranging from hundreds of atoms to tens of thousands of atoms, has been studied. Global optimization shows that all Cu and Ag nanoparticles containing 100 to 1000 atoms have an icosahedral core. Upon increasing the number of atoms to 6000 and 10,000 for Cu and Ag, respectively, the nanoparticles' structural transitions from icosahedral to truncated-octahedral. For even larger nanoparticles, the (100)/(111) surface ratio in truncated-octahedral structures increases, which finally leads to a transformation into the cuboctahedral shape as observed in experiments.

We have realized the simultaneous recovery of phosphorescence and mechanical properties for polymeric films based on covalent cross-linking between the chromophore binders and polymer matrix.