Supported ruthenium is an important heterogeneous catalyst that is used in many transformations involving biomass valorization. Most of these transformations are performed in liquid water under the presence of other gas phase species i.e. a pressure of hydrogen. It is, therefore, imperative to investigate the surface state of the underlying Ru catalyst under varying conditions of temperature, pressure and solvent. Using periodic-DFT aided ab-initio thermodynamics, we have studied the surface state of the Ru catalyst in both liquid or gas water with or without an external pressure of hydrogen. More than 800 configurations involving adsorption of H/O/OH/H2O species on 3 different Ru surfaces were randomly generated and were converted into thermodynamic maps in terms of temperature and pressure of H . The solvation effects were considered using the in-house developed Solvhybrid package which implements a hybrid QM/MM approach and makes use of fitted UFF parameters, point charges from DFT calculation and an alchemical transformation based on thermodynamic integration. Our results show that under a pressure of hydrogen the most stable phase is a monolayer of H both with and without solvation effects. However, if little or no hydrogen pressure is supplied, the surface tends to oxidize by O/OH species reaching a monolayer of oxygen at temperatures above 400 K. Surprisingly, the monolayers of H/O are more solvated compared to the intact or partially dissociated monolayer of H O. Then, those results are compared and contrasted with the one obtained on small supported Ru particles (Ru10) on TiO2. These results should help in our understanding of the Ru-based catalysts and help rationalize the increased reactivity of Ru catalysts in water in terms of its ability to generate O/OH moieties on the surface.