Computational Insight into Selective Hydrogenolysis over Monomeric MoOx-Modified Rh Catalysts in the Aqueous Phase

The reaction mechanism of hydrogenolysis over monomeric MoO_x-modified Rh catalysts is investigated by density functional theory-based molecular dynamics simulations. By explicitly treating the surrounding water molecules, the free energy surfaces are constructed for the aqueous-phase hydrogenolysis reaction. Ethylene glycol is employed as a model substrate, and it is shown that the attack of surface hydride-like species on the carbon atom at a position adjacent to the alkoxide ad-species via the S_N2 reaction facilitates the cleavage of the C–O bond and it is more efficient than the attack on the carbon atom of alkoxide ad-species. Our study of the S_N2 mechanism of the Rh–MoO_x catalyst offers insight into the reaction mechanism of hydrogenolysis in the aqueous phase for metal nanoparticles modified with metal-oxide species and the design of selective catalysts for hydrogenolysis and other related reactions of biomass-derived feedstocks.