Selective electrocatalytic reduction of carbon dioxide to formate by a trimetallic Sn-Co/Cu foam electrode

The selectivity of electrochemical reduction of CO2 to formate in an aqueous NaHCO3 solution was investigated with a series of trimetallic electrodes composed of different weight percentages of SnCo coated on copper foam (Cu-f). The maximum Faradaic efficiency of 72.2% was obtained with a Sn-95-Co-5/Cu-f electrode at a potential of -1.36 V. The Sn-95-Co-5/Cu-f electrode has a formate production rate of 1.12 mmol h(-1), which is 16.7, 1.2, and 2.3 times higher than uncoated Cu-f, Cu-f coated with Sn, and Cu-f coated with Co, respectively. Analysis of the surface of the Sn-95-Co-5/Cu-f electrode shows the formation of a composite layer of SnOx and Co3O4 ensuring good electrical conductivity and CO2 absorption. These results in combination with linear sweep voltammetry indicate that the coating of SnCo on a porous copper scaffold resulted in the fabrication of a promising electrochemical catalyst, which can greatly increase the electrocatalysis selectivity for CO2 reduction to formate.