Thermal Chemistry of Water Adsorbed on Clean and Oxygen-Predosed V(100) Single-Crystal Surfaces

The adsorption of water on V(100) single-crystal surfaces was characterized by temperature programmed desorption and X-ray photoelectron spectroscopy. On clean surfaces, the adsorption of water was determined to be dissociative, and dissociation to be favored at low coverages. With the aid of deuterium and 18 O isotope labeling, it was found that coadsorbed surface oxygen blocks this dissociation but also opens a new reaction channel that relies on hydrogen bonding to enhance the generation of hydroxide surface species. The new reaction channel is seen throughout all stages of oxygen uptake, even after the formation of a thin surface oxide film. Three water desorption states were identified in the oxygen-treated substrates, corresponding to recombination of hydroxide surface groups, decomposition of hydrogen-bonded stabilized water, and molecular desorption, respectively.