Electrochemical reduction of CO2 at the earth-abundant transition metal-oxides/copper interfaces

Electrochemical reduction of CO2 to value-added fuels and chemicals suffers from high overpotentials and poor product selectivity due in part to lack of high-performance catalysts. In this study, we investigated CO2 reduction to C1 products at the metal-oxide/copper interface, focusing on the earth-abundant transition metals, including Fe, Co and Ni, based on the results of density functional theory (DFT) calculations. Our results indicate that CO2 reduction to CO(g), HCOOH(l) and H2CO(l) is not favorable at the interfacial sites, modeled as (MO)4/Cu(100). CO2 reduction on (FeO)4/Cu(100) leads to the formation of CH4(g) at a low limiting potential of - 0.18 V. On (CoO)4/Cu(100), CO2 can be reduced to CH4(g) at a limiting potential of - 0.48 V but a solvent with permittivity constant (epsilon r) less than 70 (e.g. in propylene carbonate) can steer the reaction to produce CH3OH(l). On (NiO)4/Cu (100), CH3OH(l) is the most favorable product at a limiting potential of - 0.28 V. These results demonstrate that the presence of the metal oxide/Cu interface lowers significantly the limiting potentials of electrochemical CO2 reduction from that on Cu. Furthermore, the activity and product selectivity can be regulated by tuning the nature of (MO)4/Cu(100) and selecting appropriate solvent.