Towards a Realistic Surface State of Ru in Aqueous and Gaseous Environments

Identifying the surface species is critical towards a realistic understanding of supported metal catalysts working in water. To this end, we have characterized the surface species present at a Ru/water interface by employing a hybrid computational approach involving an explicit description of the liquid water and a possible pressure of H2. On close-packed, most stable Ru(0001) facet, the solvation tends to favor the full dissociation of water into atomic O and H in contrast with the partially-dissociated water layer reported for ultra-high vacuum conditions. The solvation stabilization was found to be as high as -0.279 J.m2 which results in stable O and H species on Ru(0001) in presence of liquid water even at room temperature. Conversely, introducing even a small H2 pressure (10−2 bar) results in a monolayer of chemisorbed H at the interface, a general trend found on the three most exposed facets of Ru nanoparticles. While hydroxyls were often hypothesized as possible surface species at the Ru/water interface, this computational study clearly demonstrates that they are not stabilized by liquid water and are not found in realistic reductive catalytic conditions.