Conventional production of carbon-based fuels and chemicals contributes significantly to greenhouse gas emissions and climate change, increasing the urgency to develop mitigation or capture technologies. Electrochemical carbon dioxide/monoxide reduction (COxRR) is a promising alternative route for production of carbon-based fuels and chemicals; it requires mild electrolyzer operating conditions, integrates well with renewable energy sources, and enables flexibility of possible product selectivity. Engineering tunable systems is necessary to ensure critical chemicals and fuels are produced according to their relative demand. Although products with one or two carbons can be formed with reasonable selectivity on copper (Cu), tunability must be improved to enable production of longer carbon chain molecules. Ethylene acts as a chain initiator itself as well as a source of C1 monomer species which promote chain propagation and can potentially improve COxRR tunability as in Fischer-Tropsch. A custom cell was designed to perform COxRR experiments with ability to control flow rates of COx and ethylene separately. Preliminary data suggests that ethylene increases the amount of methane, ethane, and propane formed and generates higher current compared to baseline COxRR with only CO2, both on Cu and in 0.1M potassium bicarbonate. Longer chain products also begin forming at lower absolute potentials than that of the baseline. Gaseous and liquid products are analyzed as a function of COx and ethylene flow rates, applied potential, and reaction environment. Considering other possible additives, biofuel production generates byproducts like oxalates, acetaldehydes, and glyoxylic acids. These bioprivileged molecules can be repurposed and added to COxRR feedstreams to act as chain propagators. Co-electroreduction of COx and oxalate are investigated for novel product distributions as a function of electrolyte concentration and pH. Both additive strategies ultimately inform the viability of CO2RR as a greener pathway to carbon-based fuels and chemicals.

COx electrochemical reduction with additive molecules towards longer chain products

ACS Fall 2021

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