(318e) Influence of Chlorine Adsorption on the Thermodynamic Wulff Shape of Ag Nanocrystals

It has been shown experimentally that chlorine can promote the formation of monodisperse Ag nanocubes with sharp corners and edges in the polyol synthesis. However, the role of Cl in the shape-control mechanism of Ag nanocubes remains elusive. Here, we examine how the adsorption of Cl influences the thermodynamic Wulff shape of Ag nanocrystals, where we use density functional theory and ab initio thermodynamics to calculate the surface energy as a function of the Cl chemical potential / solution-phase concentration of Cl. At each Cl chemical potential, the minimum surface energies of Cl-adsorbed Ag(100) and Ag(111) surfaces at different Cl coverages are used to construct the Wulff shape of Ag nanocrystals. Our calculations show that Cl adsorption can change the ratio of surface energies such that the formation of cubes with small truncated corners is thermodynamically favorable, in contrast with the Wulff shape of bare Ag surfaces which is a cubooctahedron. In addition, we find that mixed substitutional+on-surface adsorption becomes more stable than on-surface adsorption at high Cl coverages, which could facilitate the formation of AgCl structures at large solution-phase concentrations of Cl. Our study indicates that the adsorption of Cl can impart significant thermodynamic-shape change, favoring the formation of Ag nanocubes.