The configuration and electronic state of SO 3 adsorbed on Au surface

Abstract

We evaluated the adsorption of SO 3 molecule on Au (1 1 1) surface using first principles calculation by a slab model with a periodic boundary condition. We find that there are six stable adsorption configurations on an Au surface, where the SO 3 molecule is adsorbed above the three-fold fcc and hcp hollow sites and on the atop site. In two of these configurations, S and two O atoms are bound to the Au atoms, the next two configurations have all the three O atoms bound to the Au surface atoms, and the last two configurations have the S atom bound to an Au surface atom on the atop site and O atoms situated above the hollow sites. In these configurations, the electronic structures of SO 3 on the Au surface show that molecular orbitals of SO 3 and those of the Au surface are hybridized in the active metal d-band region, that the localized molecular orbitals in SO 3 are stabilized, and that charge is transferred from Au to S 3p by SO 3 adsorption on the Au surface though there is little other interaction of the S and O (bound to Au) component with Au. Moreover, the bond between the S and O atoms bound to Au is weakened due to SO 3 adsorption on the Au surface due to the charge polarization of the O–Au bond. This interaction is likely to encourage the S–O bond to break.