Adsorption and dissociation of H2O on Au(1 1 1) surface: A DFT study

Abstract

Periodic density functional theory (DFT) calculations using plane waves were performed to systematically investigate the stable adsorption of H2O on Au(111) surface and the corresponding dehydrogenated reaction. The equilibrium configuration on top, bridge, and hollow (fcc and hcp) site were determined by relaxation of the system. The adsorptions of H2O on top site and OH on bridge site are favorable on Au(111) surface, while the adsorption of O on hollow(fcc) site is preferred. The adsorbates are adsorbed on the gold surface due to the interaction between p orbital of adsorbates and d orbital of gold atoms, and the interaction is more evident on the first layer than that on any others. We also investigated the dissociation reaction of H2O on clean and oxygen-covered gold surface. The results show that the hydrogen atom dissociating from H2O need the energy of 255.54kJ/mol on clean gold surface, while the dissociating energy decreases to 44.61kJ/mol with the aid of adsorbed O atom (Oads). These phenomena indicate that the dehydrogenated reaction energy barrier on the pre-covered oxygen gold surface is lower and Oads can promote the dehydrogenation of H2O.