Adsorption and decomposition of SOx (x = 1, 2, 3) on Au(001) surface: A DFT-based study with van der Waals correction

Abstract

Using the first-principles density functional theory (DFT) calculation, including the effect of van der Waals (vdW) dispersion, we investigate the adsorption and decomposition of sulfur oxides SOx (x = 1, 2, 3) molecules on the gold (Au) surface, i.e., Au(001). Two coverages (θ) of SOx have been considered, which are 0.11 ML and 0.22 ML. We determine the adsorption energy, charge transfer, and the nature of bonding between the Au surface and the molecule. Also, we employ thermochemistry to study the SOx decomposition. We have found that for all the configurations of SOx (x= 2, 3) on the Au(001), the use of the standard GGA-PW91 functional results in an unstable SOx/Au(001) structures, irrespective of the coverage. Including the vdW dispersion however stabilizes the respective SOx/Au(001) structural configurations. Also, there is a charge transfer from the molecule to the Au (001) surface in the case of SOx/Au (001) (x =1, 2), for the two coverages considered. However, for SO3 /Au (001) configurations, charge transfer is dependent on the molecular coverage such that for θ = 0.11 ML, charges are transferred from the surface to the molecule while the reverse occurs for θ = 0.22 ML. Furthermore, we found that while the calculated adsorption energy suggests that the Au (001) surface is able to adsorb the molecules, it may not be energetically feasible to decompose the SOx (x= 1, 2, 3) molecules on the Au (001) surface. This study contribute to computational efforts aim at finding suitable substrates to capture and decompose hazardous sulfur oxide molecules from industrial processes, vehicle emission or similar sources.