Ethylene Electrosynthesis via Selective CO₂ Reduction: Fundamental Considerations, Strategies, and Challenges

The electrochemical carbon dioxide reduction reaction (CO₂RR) is a promising approach for reducing atmospheric carbon dioxide (CO₂) emissions, allowing harmful CO₂ to be converted into more valuable carbon-based products. On one hand, single carbon (C₁) products have been obtained with high efficiency and show great promise for industrial CO₂ capture. However, multi-carbon (C₂₊) products possess high market value and have demonstrated significant promise as potential products for CO₂RR. Due to CO₂RR's multiple pathways with similar equilibrium potentials, the extended reaction mechanisms necessary to form C₂₊ products continue to reduce the overall selectivity of CO₂-to-C₂₊ electroconversion. Meanwhile, CO₂RR as a whole faces many challenges relating to system optimization, owing to an intolerance for low surface pH, systemic stability and utilization issues, and a competing side reaction in the form of the H₂ evolution reaction (HER). Ethylene (C₂H₄) remains incredibly valuable within the chemical industry; however, the current established method for producing ethylene (steam cracking) contributes to the emission of CO₂ into the atmosphere. Thus, strategies to significantly increase the efficiency of this technology are essential. This review will discuss the vital factors influencing CO₂RR in forming C₂H₄ products and summarize the recent advancements in ethylene electrosynthesis.