Electrochemical\nConversion of CO<sub>2</sub> to Methyl\nFormate in a Flow Electrolyzer with Mixed Propylene Carbonate/Methanol\nCatholyte

Despite the promise of electrochemical carbon dioxide\nreduction\nas a technology for the production of clean fuels and decarbonization\nof the chemical industry, research has mostly focused on aqueous systems\nwith a relatively limited set of products that have been achieved\nvia electrosynthesis. Increasingly, CO<sub>2</sub> electroreduction\nin nonaqueous solvents is being pursued to develop new avenues for\nexpanding the suite of products that can be made with high selectivity.\nCO<sub>2</sub> reduction in alcohols coupled with in situ esterification\nto produce esters is one such route that utilizes nonaqueous electrolyte.\nTo be practical, such electrochemical syntheses need to be translated\nto a high-performance reactor such as a flow electrolyzer. However,\nmany organic solvents, such as alcohols, wet and flood porous electrodes,\nthus impeding reactor performance. In this work, methanol was mixed\nwith propylene carbonate as a catholyte for a gas-fed CO<sub>2</sub> flow electrolyzer that avoided cathode flooding. Simultaneously,\na dual aqueous anolyte was used for water oxidation as a scalable\nand sustainable anodic half-reaction. The performance effect of methanol\nconcentration, catholyte acidity, CO<sub>2</sub> flow rate, and dilute\nwater in the catholyte were investigated. With 10 vol % methanol in\n90 vol % propylene carbonate, 63% faradaic efficiency for methyl formate\nester product was sustained without cathode flooding. However, improvements\nare still needed to lower the cell resistance and further increase\nthe operating current density.