Elucidating the Role of the Mo₂C/MgO Catalyst Interface in the Mechanism of the Reverse Water Gas Shift Reaction

The reverse water gas shift reaction (RWGS) is a key step in the valorization of CO₂ to value-added products such as fuel. Metal carbides, particularly molybdenum carbide (Mo₂C), supported on transition metal oxide supports have been reported as promising materials to be used as catalysts for the low-temperature RWGS reaction. A deeper understanding of catalyst support interactions can be greatly beneficial for the development of better and more efficient catalysts in the future. To this end, this study computationally investigated the effect of the interaction between the Mo₂C(001) surface and the MgO(001) surface on the RWGS mechanism. The RWGS mechanisms were explored at the Mo₂C/MgO interface, as well as on the bare surface of Mo₂C. While the pathway at the interface went through an associative-type mechanism and a carboxylate intermediate, the Mo₂C surface was found to go through a redox-type mechanism. Interestingly, both the kinetics and thermodynamics of each pathway were similar, suggesting that the observed differences in the CO₂ hydrogenation pathways were primarily limited by the diffusion of CO₂ across the MgO surface rather than inhibitory energetics resulting from the interplay of the Mo₂C material and MgO support.