Theoretical Study of the Reverse Water Gas Shift Reaction on Copper Modified β-Mo2C(001) Surfaces

The reverse water gas shift (RWGS) reaction has attracted great attention in recent years. It is well-known that supported catalysts, especially single-atom catalysts (SACs), exhibit good catalytic activity in many reactions. Thus, we designed the single-atom catalyst (SAC) Cu@Mo2C(001) and the smallest copper cluster catalyst Cu4@Mo2C(001) for the RWGS reaction. In this study, density functional theory (DFT) calculations were used to explore the reaction mechanisms of the RWGS reaction on the surfaces of Cu@Mo2C(001) and Cu4@Mo2C(001). The dissociative adsorption of H2 on these two surfaces is barrier-free and highly exothermic, which is beneficial to the RWGS reaction. Importantly, three possible mechanisms—the COOH mechanism, HCOO mechanism, and redox mechanism—have been discussed. The results illustrated that the redox mechanism is the most feasible pathway among the Cu@Mo2C(001) and Cu4@Mo2C(001) surfaces. By comparing the activation barrier of the rate-limiting step of the redox mechanism on the two surfaces, the results showed that the activation barrier of the rate-limiting step on the Cu4@Mo2C(001) surface is smaller, which is more conducive to the progress of the RWGS reaction. Therefore, the tactic of introducing non-noble copper could be a promising way to design highly efficient catalysts.