Efficient Conversion of CO₂to Formate Using Inexpensive and Easily Prepared Post-Transition Metal Alloy Catalysts

Developing affordable electrocatalysts to facilitate the reduction of carbon dioxide (CO 2 ) to high-value products with high selectivity, efficiency, and large current densities is a critical step for the production of liquid carbon-based fuels. In this work, we show that inexpensive post-transition metals [tin (Sn) and lead (Pb)] and their alloys (PbSn) are excellent cathode materials to reduce CO 2 in an ionic liquid/acetonitrile/water electrolyte media. Electrochemical impedance spectroscopy measurements show that the PbSn alloys exhibit lower charge-transfer resistance when compared to the pure metal electrodes, as supported by electronic structure calculations. Current densities as high as 60 mA/cm 2 are observed with optimal mixtures of ionic liquid, acetonitrile, and water. Reduction product analysis identifies carbon monoxide (CO) and formate (HCOO−) as primary reduced products, with higher selectivity toward formate. Faradaic efficiency for formate on pure Pb and pure Sn was determined to be 80 ± 4 and 86 ± 3%, respectively. FE % improves as either Pb is incorporated into Sn or vice versa, and there is a maximum FE of 91 ± 3% for both 50 and 40% Pb composition.