Electrochemical Reduction of CO2 to Ethylene with Coproduction of Glycolic Acid Via Glycerol Oxidation

We are in a race against time to implement technologies for carbon capture, conversion, and utilization (CCU) to create a closed anthropogenic carbon cycle. Renewable energy powered electrochemical CO 2 reduction (eCO 2 R) to fuels and chemicals is an attractive technology in this context. Here, we demonstrate a strategy to drive economic feasibility of eCO 2 R to ethylene (C 2 H 4 ), the largest produced organic chemical, by coupling with glycerol oxidation on anode. Our gold nano-dendrite anode catalyst demonstrated very high activity (J ~377 mA/cm 2 at 1.2 V vs RHE) and selectivity (~50% to glycolic acid (GA)) for glycerol oxidation. The co-electrolysis process demonstrated record high selectivity of ~60% for C 2 H 4 production at a very low cell voltage of ~ 1.7 V, translating to 32% reduction in required energy compared to conventional eCO 2 R with water oxidation reaction on anode. The experimental results were complemented with a detailed technoeconomic analysis that indicated economic feasibility will depend on several factors such as price of organic feed, selectivity of anode electrode, market value of chemicals produced and most importantly cost of separation and purification. Our results indicate that C 2 H 4 produced via conventional eCO 2 R would require electricity price to plummet to <1 cents/kWh to be cost-competitive, while a co-electrolysis process to produce C 2 H 4 and GA will help reduce C 2 H 4 production cost by ~ 80 % to ~1.08 $/kg, reaching cost parity at electricity price of 5 cents/kWh. This study may trigger research efforts for design of electrochemical processes with low electricity requirement using cheap industrial waste streams.