Electrochemical CO 2 Reduction to Methyl Formate/Formic Acid in a Dual Non-Aqueous/Aqueous Flow Cell Electrolyzer

Electrochemical conversion of CO 2 has been very promising in neutralizing existing carbon in the atmosphere as well as creating a pathway to produce various fuels and chemicals. The use of a CO 2 flow electrolyzer makes it possible to achieve high faradaic efficiencies at high current densities from pure CO 2 or dilute flue gas feeds. CO 2 solubility in methanol is higher than in aqueous solutions and with acidic methanol as a solvent, it is possible to generate a unique product, methyl formate. This work describes the use of mixed propylene carbonate/methanol solutions as a solvent for CO 2 reduction using a gas diffusion electrode and an aqueous anolyte and optimization of a high mass flux CO 2 electrolyzer to produce methyl formate using a Pb-catalyst at higher current densities. pH-dependent product distribution is also described. The partial current densities varied depending on the cell design; cells where charge passes through more solvent result in lower current density because methanol has a higher solution resistance than aqueous solutions. The methanolic catholyte is paired with an aqueous anolyte to promote a sustainable water oxidation half-reaction.