Electrochemical Reduction of Carbon Dioxide to Formate on Tin-Lead Alloys

Electrochemical reduction of carbon dioxide (CO2) to formate (HCOO-) in aqueous solution is studied using tin-lead (Sn-Pb) alloys as new electrocatalysts. In electrochemical impedance spectroscopy (EIS) measurements, lower charge-transfer resistance is observed for the alloy electrodes when compared to the single metal electrodes such as Sn and Pb. The results of X-ray photoelectron spectroscopy (XPS) and cyclic voltammetric (CV) analysis show that the Sn in the Sn-Pb alloys facilitates the formation of oxidized tin (SnOx) and metallic lead (Pb-0) on the alloy surface by inhibiting the formation of low-conductive lead oxide (PbO) film. The CV analysis confirms that the Sn-Pb alloys exhibit higher reduction current than the single metal electrodes under CO2 atmosphere. The Faradaic efficiency (FE) and the partial current density (PCD) of HCOO- production on the alloy electrodes is investigated by electroreduction experiments at -2.0 V (vs Ag/AgCl) in an H-type cell. As results, respectively more than 16% and 25% higher FE and PCD of HCOO- are obtained from the Sn-Pb alloys compared to the single metal electrodes. A Sn-Pb alloy including surface composition of Sn56.3Pb43.7 exhibits the highest FE of 79.8% with the highest PCD of 45.7 mA cm(-2).