Hexagonal Cu(111) Monolayers for Selective CO₂ Hydrogenation to CH₃OH: Insights from Density Functional Theory

Cu-based heterogeneous catalysts are the most active and promising catalysts for selective CO2 hydrogenation. Density functional theory (DFT)-based calculations have been performed to gain insight into the suitability of Cu monolayer (ML)-based catalysts for selective CO2 hydrogenation. Four different types of Cu MLs [hexagonal and orthorhombic; Cu(111) and Cu(110)] have been modeled, and the stabilities of the such ML-based structures have been investigated from formation energy, cohesive energy, and phonon dispersion calculations. The catalytic activities of the most stable hexagonal Cu(111) ML have been investigated for CO2 hydrogenation reactions. All of the possible CO2 hydrogenation pathways have been systematically studied on the Cu(111) ML surface, and then our results are compared with that of the bulk Cu(111) suface and Cu nanocluster (NC)-based catalysts. Our detailed investigation shows that such a ML-based catalyst is highly selective (CH3OH vs CH4) compared to the previously reported Cu-based catalysts. Besides, it works under a low working potential (0.46 V) compared to the previously reported bulk Cu(111) surface (0.71 V) and Cu NC-based (0.53 V) catalysts.