One of the most central challenges of this century is undoubtedly to address the energy dilemma effectively, where sustainability and environmental footprints must be addressed without one aspect outweighing the other. This mandates a multidisciplinary approach to develop and commercialize several novel technologies that produce sufficient energy to meet the ever-growing global demand yet reducing the greenhouse gas (GHG) emissions worldwide. Catalysis plays a key role in this transformation by enabling sustainable production of energy, fuels, and chemicals with lower costs and environmental impacts. In this work, development of an active and stable catalyst for activating water is explored, for abstracting hydrogen towards carrying out hydroprocessing reactions for the in-situ upgrading technology, ISUT, a technique that integrates in-reservoir upgrading and recovery in one single process. In this method, the lowest quality fraction of oil is being separated aboveground and being re-injected with hydrogen, in the presence of nano-catalyst, to carry out hydroprocessing reactions downhole to produce upgraded quality oil. In this work, a highly active hydrogenating catalyst, sulfide bimetallic NiMo catalyst, is prepared using a novel method that employs ultrasonication for production of oil-in-water micro-emulsions in order to obtain particle size as small as 30 nm. The small particle size in return offers high catalytic activity, as evidenced by analyzing reduction of heteroatoms in oil and improving viscosity and density and suppressing tendency to form coke. Next, this active catalyst is tested in hybrid environments that consist of water in different molar ratios to that of hydrogen. The sulfide NiMo catalyst hydrogenation activity was closely followed using model molecules under different environments. The NiMo catalyst was found to be intolerant to the presence of water and its hydrogenation of capability was considerably suppressed in the presence of water. It is proposed that water may oxidize the sulfide phase of the catalyst. However, removal of water and under the presence of hydrogen, the hydrogenation activity of the catalyst was progressively retrieved. Since it was evidenced the NiMo catalyst suffered from instability in the presence of water, a cubic molybdenum carbide catalyst was synthesized and used for carrying out ISUT experiments with different steam partial pressures. Several control experiments including thermal, catalytic under hybrid environments where an inert gas such as nitrogen replaces either of the two reacting gases, hydrogen or steam, were carried out to evidence water dissociation on the α-MoC1-x catalyst. In addition, O atom in water were isotopically labelled, i.e. H218O, to elucidate the mechanism of water activation during ISUT reactions. Using the isotopically labelling of O atom in water, it was verified that the α-MoC1-x catalyst is capable of water dissociation at the process conditions in this work. In addition, the catalyst showed capability for simultaneous hydrogenation and water dissociation. However, studying several experiments the co-presence of hydrogen showed to have an impeding effect on water activation, yet it does not completely stop water dissociation. These studies include ISUT reactions and adsorption reactions to better understand such effects.