The reaction pathways for HSCH3 adsorption on Au(111): a density functional theory study

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• Methanethiol (CH3SH) adsorption on metal surfaces is crucial for understanding catalysis and material functionalization.
• Previous studies have explored various adsorption states, but the dissociation pathways remain incompletely understood.

Purpose of the Study:

• To investigate the adsorption and dissociation reaction pathways of methanethiol (CH3SH) on the Au(111) surface using density functional theory.
• To determine the energetic favorability and activation barriers for different reaction pathways.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Investigated adsorption states, dissociation processes, and transition states on the Au(111) surface.
• Considered surface relaxation effects for improved accuracy.

Main Results:

• A stable molecular adsorbed state of CH3SH was identified, with the sulfur atom bonded to Top sites, and adsorption is nonactivated.
• The dissociation of CH3SH into methylthiolate (CH3S) and hydrogen (H) is energetically unfavorable, becoming slightly exothermic only with surface relaxation.
• All reaction pathways exhibit significant activation energy barriers, with the lowest calculated barrier being approximately 0.52 eV (0.41 eV with slab relaxation).
• The transition state for dissociation features the sulfur atom on a Top site and the hydrogen atom near a Bridge site.

Conclusions:

• The high activation energy barrier for dissociation explains the experimental observation of minimal reactive methanethiol dissociation on Au(111).
• DFT calculations provide valuable insights into the surface chemistry of methanethiol on gold, guiding future experimental and theoretical studies.