First-principles study of copper nanoclusters for enhanced electrochemical CO2 reduction to CH4

The conversion of carbon dioxide (CO2) into usable hydrocarbon fuels is important for recycling carbon resources and mitigating environmental problems. However, converting CO2, which is a stable compound, requires a high additional energy. Therefore, it is essential to understand the electrochemical reduction mechanisms of CO2 and develop more efficient catalysts. In this study, density functional theory calculations were performed to examine electrochemical CO2 reduction on copper nanoclusters (NCs) (ails NCs and Cuss NCs) and the Cu(1 11) surface to verify the effect of the surface geometry and size of the NCs on the conversion of CO2 into CH4. The highest energy barriers to CO2 reduction (i.e., the potential-limiting step) on the Cu-13 NCs (0.64 eV), Cuss NCs (0.83 eV), and Cu(1 11) surface (0.86 eV) lie in the CO* -> CHO* step. The formation of an adsorbed CHO intermediate depending on the catalyst surface geometry may significantly influence the energy barrier, as demonstrated by analyses of the electronic properties, such as the density of states, charge density difference, and highest occupied molecular orbital and lowest unoccupied molecular orbital band gap. (C) 2017 Elsevier B.V. All rights reserved.