Developing
affordable electrocatalysts to facilitate the reduction
of carbon dioxide (CO2) 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
CO2 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/cm2 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.