Influence of adsorbates on the segregation properties of Au–Pd bimetallic clusters

• Surface segregation upon adsorption is studied by Monte Carlo simulations.
• Pd atoms occupy the surface sites for Au–Pd clusters upon CO and O adsorption.
• The Au surface segregation of free cluster is completely reversed at the high CO and O coverage.

In this work, we investigate the surface segregation phenomena of 923-atom Au–Pd bimetallic clusters upon CO and O adsorption by using Monte Carlo simulations. The metal–metal interaction was modeled by the Johnson’s embedded atom method (EAM) and the metal–adsorbate interaction potential was developed by density functional theory (DFT) calculations. It is found that Pd atoms would like to occupy the surface sites for Au–Pd clusters upon adsorption, which is different to the surface segregation of Au on the surface of free Au–Pd clusters. This phenomenon may be due to a competition between surface energies of Au and Pd metals and their interaction strength with CO and O for the clusters upon adsorption. It is expected that our results can be used to understand and explain the experimental results of Pd atoms occupying the surface layer of Au–Pd bimetallic clusters in reactive environments.