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 (Pb0) 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.