Hydroxyl Chain Formation on the Cu(110) Surface: Watching Water Dissociation

Abstract

The formation of hydroxyl chains from water dissociation on the Cu(110) surface has been studied by using a combination of scanning tunneling microscopy (STM), electron stimulated desorption ion angular distribution (ESDIAD), temperature programmed desorption (TPD), and density functional theory (DFT) calculations. Annealing the D2O-covered surface to a temperature of ∼200 K leads to desorption of D2O molecules and produces a zigzag structure due to adsorbed OD groups with a periodicity of 5 A along the direction in the STM image. Coadsorption of O2 promotes the water dissociation reaction and produces hydroxyl chains with much higher coverage. ESDIAD measurements show a two-beam pattern consistent with OD(a) species inclined ∼40° with respect to the surface normal and orientated along the azimuth. The calculations reveal the existence of stable chain structures comprised solely of hydroxyl groups as well as of interacting water and hydroxyl groups that are consistent with the observed STM image.