Sequential Cascade Electrocatalytic Conversion of Carbon Dioxide to C-C Coupled Products

Cascade catalytic processes perform multi-step chemical transformations without isolating the intermediates. Here, we demonstrate a sequential cascade pathway to convert CO2 to C2+ hydrocarbons and oxygenates in a two-step electrocatalytic process using CO as the intermediate. CO2 to CO conversion is performed by using Ag and further conversion of CO to C-C coupled products is performed with Cu. Temporal separation between the two reaction steps is accomplished by situating the Ag electrode upstream of the Cu electrode in a continuous flow reactor. Convection-diffusion simulations and experimental evaluation of the electrodes individually were performed to identify optimal conditions. With the upstream Ag electrode poised at -1 V vs RHE in a flow of CO2-saturated water in aqueous carbonate buffer, over 80% of the CO can be converted on the downstream Cu electrode. When the Ag electrode is on, a supersaturation of CO is achieved near the Cu electrode, which leads to a relative increase in the formation rate of C2 and C3 oxygenates as compared to ethylene.