(507a) Electrocatalytic Conversion of CO2 to Fuels On Metal Surfaces

In order to fully understand the electro-reduction of CO2 on metal surfaces, one must investigate a wide range of metals with differing electronic and geometric structures, and study reaction activity and selectivity under a wide range of applied potentials as mechanistic pathways can change drastically.   An experimental setup for running reproducible electrocatalytic CO₂ reduction with on-stream gas analysis and ex-situ liquid analysis is presented; our results lead to a greater understanding of catalytic processes at the metal surfaces.  The combination of gas chromatography, proton nuclear magnetic resonance (NMR), and 13C-NMR yields accurate quantitative analysis of H₂, CO, hydrocarbons, formate, and alcohols.  Using our optimized CO₂ reduction setup, we proceeded to look at a variety of metal surfaces including Au, Pt, Cu, Ag, Zn, Ni and Fe, measuring all reaction products, major and minor, down to 0.01% current efficiency.  As previously reported, these materials can be grouped into three categories: Au and Ag which have selectivity for CO formation, Ni, Fe and Pt which produce primarily H₂ and Cu which yields a high fraction of hydrocarbons.  We aim to elucidate the reaction pathways which lead to the observed selectivity, and propose ways to improve selectivity and reduce the required overpotential for production of desirable products, namely hydrocarbons or alcohols.