One-step electrosynthesis of ethylene and ethanol from CO₂ in an alkaline electrolyzer

Electroreduction of CO₂ has potential for storing otherwise wasted intermittent renewable energy, while reducing emission of CO₂ into the atmosphere. Identifying robust and efficient electrocatalysts and associated optimum operating conditions to produce hydrocarbons at high energetic efficiency (low overpotential) remains a challenge. In this study, four Cu nanoparticle catalysts of different morphology and composition (amount of surface oxide) are synthesized and their activities towards CO₂ reduction are characterized in an alkaline electrolyzer. Use of catalysts with large surface roughness results in a combined Faradaic efficiency (46%) for the electroreduction of CO₂ to ethylene and ethanol in combination with current densities of ∼200 mA cm^-2, a 10-fold increase in performance achieved at much lower overpotential (only < 0.7 V) compared to prior work. Compared to prior work, the high production levels of ethylene and ethanol can be attributed mainly to the use of alkaline electrolyte to improve kinetics and the suppressed evolution of H₂, as well as the application of gas diffusion electrodes covered with active and rough Cu nanoparticles in the electrolyzer. These high performance levels and the gained fundamental understanding on Cu-based catalysts bring electrochemical reduction processes such as presented here closer to practical application.