The development of affordable electrocatalysts that can facilitate the reduction of carbon dioxide (CO2) to value-added products with high selectivity, efficiency, and large current densities is a critical step for the renewable production of liquid carbon-based fuels. In this work, we show that inexpensive post-transition metals (tin (Sn) and lead (Pb)) and their alloys are excellent cathode materials to reduce CO2 in an ionic liquid/acetonitrile/water electrolyte media. Room temperature ionic liquids (RTILs), especially those featuring cations that interact with CO2, may be advantageous in terms of (i) lowering the overpotential for CO2 reduction by activating CO2 via complexation and (ii) suppressing the hydrogen evolution reaction (HER) on the surface of the electrode by site blocking. The amphiphilic properties of acetonitrile allow it to better solvate the ionic liquid than pure water via improved interactions with the polar and nonpolar regions of the RTIL. Water is still important to the electrolyte mixture as a potential proton source. Electrochemical impedance spectroscopy (EIS) measurements show that the Sn/Pb alloys exhibit lower charge-transfer resistance when compared to the pure metal electrodes. Current densities as high as 50 mA/cm 2 are observed with optimal mixtures of ionic liquid, acetonitrile, and water. Reduction product analysis reveal carbon monoxide (CO) and formate (HCOO-) as reduced products. CO is an important C1 precursor for Fischer–Tropsch synthesis (FTS) for a sustainable production of carbon-based fuels. Formate or formic acid (HCOOH) is a valuable product which can be used directly in a formic acid fuel cell.

Electrochemical reduction of carbon dioxide to formate and carbon monoxide on lead−tin alloys

2019 Fall National Meeting

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