Theoretical study of the catalytic performance of Fe and Cu single-atom catalysts supported on Mo2C toward the reverse water-gas shift reaction.

The reverse water-gas shift (RWGS) is an attractive process using CO2 as a chemical feedstock. Single-atom catalysts (SACs) exhibit high catalytic activity in several reactions, maximizing the metal use and enabling easier tuning by rational design than heterogeneous catalysts based on metal nanoparticles. In this study, we evaluate, using DFT calculations, the RWGS mechanism catalyzed by SACs based on Cu and Fe supported on Mo2C, which is also an active RWGS catalyst on its own. While Cu/Mo2C showed more feasible energy barriers toward CO formation, Fe/Mo2C presented lower energy barriers for H2O formation. Overall, the study showcases the difference in reactivity between both metals, evaluating the impact of oxygen coverage and suggesting Fe/Mo2C as a potentially active RWGS catalyst based on theoretical calculations.

2D carbon nitride as a support with single Cu, Ag, and Au atoms for carbon dioxide reduction reaction.

The electrochemical conversion of CO2 into value-added chemicals is an important approach to recycling CO2. In this work, we have combined the most efficient metal catalysts for this reaction, namely Cu, Ag, and Au, as single-atom particles dispersed on a two-dimensional carbon nitride support, with the aim of exploring their performance in the CO2 reduction reaction. Here, we report density functional theory computations showing the effect of single metal-atom particles on the support. We found that bare carbon nitride needed a high overpotential to overcome the energy barrier for the first proton-electron transfer, while the second transfer was exergonic. The deposition of single metal atoms enhances the catalytic activity of the system as the first proton-electron transfer is favored in terms of energy, although strong binding energies were found for CO adsorption on Cu and Au single atoms. Our theoretical interpretations are consistent with the experimental evidence that the competitive H2 generation is favored due to the strong CO binding energies. Our computational study paves the road to finding suitable metals that catalyze the first proton-electron transfer in the carbon dioxide reduction reaction and produce reaction intermediates with moderate binding energies, promoting a spillover to the carbon nitride support and thereby serving as bifunctional electrocatalysts.