Insight into the diffusion mechanism of Cu cluster over Cu(111) surface: Effect of syngas and H2S atmosphere on Cu diffusion

Abstract

Understanding the diffusion mechanism of Cu cluster over Cu surface is one of the important issues to predict and improve the stability of Cu-based catalyst. The diffusion of Cu adatom, Cu2 and Cu3 cluster over Cu(111) surface under different atmospheres (vacuum, CO, H2 and H2S atmosphere) at different temperatures have been investigated using density functional theory calculations. The results suggest that CO accelerates Cu surface diffusion at different temperatures, while H2 atmosphere has little effect depending on the temperature. Further, under H2S atmosphere, the negative formation energy of Cu-S complexes indicate that Cu-S species are more facile to form on Cu(111) surface. The diffusivity of CuS complex increases significantly with the decreasing of temperature and the increasing of H2S concentration, which suggests that ppm H2S results in the fast sintering of Cu surface significantly. This is consistent with the experimental result.