Adsorption and diffusion of sulfur on the (111), (100), (110), and (211) surfaces of FCC metals: Density functional theory calculations.

Abstract

We have studied the adsorption and diffusion of sulfur at the low-coverage regime of 0.25 ML on the (111), (100), (110), and (211) surfaces of Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au using density functional theory calculations. Sulfur adsorbed preferentially on three-fold or four-fold high-coordination sites over most of the studied surfaces. On the Ir(110), Pt(110), and Au(110) surfaces, sulfur is more stable on the two-fold sites. Calculations of the minimum energy diffusion pathway show that the energy barrier for the surface diffusion of sulfur depends on the orientation and nature of the metal surfaces. On the (100), sulfur shows the highest diffusion energy, ranging from 0.47 eV in Au(100) to 1.22 eV in Pd(100). In the (110) surface, the diffusion of sulfur is along the channel for Ni, Cu, Rh, Pd, and Ag, and across the channel for Ir, Pt, and Au. In the case of the (211) surfaces, the diffusion is preferentially along the terrace or step-edge sites. Our work provides data for the adsorption of sulfur on many surfaces not previously reported. The present work is a reference point for future computational studies of sulfur and sulfur-containing molecules absorbed on face center cubic metal surfaces.