(273a) Theoretical Insights Into the Electrochemical Reduction of CO2 Into Hydrocarbon Fuels

The production of hydrocarbons from carbon dioxide and a renewable electricity source has obvious appeal. Experimentally, copper has been shown to be the only pure metal electrode that produces hydrocarbons from the electrochemical reduction of CO₂. However, a large overpotential of ~1 V is needed to accomplish this, and the full product spectrum includes not only CH₄ and C₂H₄, but also H₂, HCOOH, and CO. In contrast, other pure metal electrodes do not produce hydrocarbons, but instead produce formic acid (Pb, Hg, Tl, In, Sn, Cd, Bi), carbon monoxide (Au, Ag, Zn, Pd, Ga), or do not react with CO₂ and instead just produce H₂ (Ni, Fe, Pt, Ti). The reason for the unique ability of Cu to catalyze the production of hydrocarbons is unknown, as is the reason for the large overpotential requirement. In the current work, we use density functional theory (DFT) calculations coupled with a computational hydrogen electrode model in order to explain the reaction mechanisms of the product spectra observed via this electrochemical reaction. The model has been found to do a remarkable job in explaining the overpotential as well as in capturing the order of appearance of the product spectra observed experimentally at copper electrodes. From this model, descriptors for electrochemical reduction of CO₂ at other surfaces are being developed.