Electrochemical Reduction of CO2 to Ethylene with 32% Lower Energy at 80% Lower Cost via Coproduction of Glycolic Acid

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 CO₂ reduction (eCO₂R) to fuels and chemicals is an attractive technology in this context. Here, we demonstrate a strategy to drive economic feasibility of eCO₂R to ethylene (C₂H₄), 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/cm² at 1.2 V vs reversible hydrogen electrode) and selectivity (~50% to glycolic acid (GA)) for glycerol oxidation. The co-electrolysis process demonstrated record high selectivity of ~60% for C₂H₄ production at a very low cell voltage of ~ 1.7 V, translating to 32% reduction in required energy compared to conventional eCO₂R 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 C₂H₄ produced via conventional eCO₂R would require electricity price to plummet to <1 cents/kWh to be cost-competitive, while a co-electrolysis process to produce C₂H₄ and GA will help reduce C₂H₄ 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.