Enhancing Dissociative Adsorption of Water on Cu(111) via Chemisorbed Oxygen

We have used X-ray photoelectron-spectroscopy to study the dehydrogenation of H2O molecules on the clean and oxygenated Cu(111) surfaces. The clean surface does not show reactivity toward H2O dehydrogenation. By contrast, H2O molecules on the oxygenated Cu(111) dissociate into OH species by reacting with chemisorbed oxygen until the complete consumption of the chemisorbed oxygen at which the surface loses its reactivity toward H2O dehydrogenation. Increasing the temperature to 200 degrees C and above decreases molecularly adsorbed H2O for dehydrogenation, thereby resulting in less loss of chemisorbed O. In conjunction with density-functional theory calculations, a three-step reaction pathway is proposed to account for the chemisorbed O assisted dehydrogenation of H2O molecules and the net loss of surface oxygen. These results provide insight into understanding the elemental steps of the dehydrogenation of H2O molecules and the controllable conditions for tuning H2O dissociation on metal surfaces.