Structure and adsorption properties of Cu-Au nanoparticles in harsh reactive environments

The reactivity of nanoparticles is governed by their surface composition, which tends to vary significantly under reactive conditions. In this study, the impacts of temperature and the presence of a CO or O2 atmosphere on the structures of Au79, Cu19Au60, Cu39Au40, Cu60Au19, and Cu79 nanoparticles were investigated using a combination of global optimization, machine learning interatomic potentials, and density functional theory. We find that increasing gold content weakens CO and O adsorption and limits oxygen-induced structural changes, while copper-rich particles undergo pronounced oxidation and reconstruction. Bader charge analysis shows that, in bare nanoalloys, Au withdraws electron density from Cu due to their electronegativity difference. In oxidized Cu-Au nanoalloys, the charge on Cu atoms depends on the number of O neighbors and can reach values typical of Cu2O (0.6 e) and CuO (1.1 e). On average, the Cu atoms exhibit positive effective Bader charges of ∼0.9 e in these nanoalloys. Our results indicate that models of Cu-Au catalysts under oxidizing conditions must incorporate the full ensemble of metallic and oxidized configurations rather than a single most probable structure to predict true catalytic activity.