Ab initio molecular dynamics study of wet H2S adsorption and dissociation on Fe(100) surface

Abstract

Oil and gas pipeline transportation media often contain acidic media, such as H2S and CO2. The corrosion behavior of oil and gas equipment in wet H2S environment affects its service life. In this paper, ab initio molecular dynamics (AIMD) is used to study the dynamic behavior of wet H2S on Fe(100) surface in 300 K, including adsorption, dissociation and diffusion. Besides, the influences of surface defects and H2S coverage are also considered. The calculation results show the primary dissociation and secondary dissociation of H2S occur successively in perfect and defective Fe(100) surface. The presence of surface defects will reduce the dissociation energy of H2S, making it more prone to dissociation to generate H and S atoms, while the increase of H2S coverage will promote the primary dissociation of H2S but inhibit the secondary dissociation. The entire simulation process suggests that the SH, H and S generated from the dissociation of H2S adsorbed preferentially in the hollow site. The adsorption of S atoms is more stable than H atoms since H could diffuse between adjacent hollow site. In addition, no H atoms diffusion into subsurface region was observed during the whole simulation process.