The impact of flue gas impurities on the electrochemical reduction of carbon dioxide with copper catalysts

Abstract

The direct electrochemical reduction of CO₂ to C₂₊ products from flue gases is a promising route to convert waste CO₂ into valuable products without expensive capture and purification steps. However, impurities may hamper the efficiency and stability. Here we investigate the impact of N₂, O₂, SO₂ and NO on CO₂ electrolysis with Cu catalysts. While N₂ causes a diluting effect without side reactions, O₂ is responsible for a parasitic reduction reaction that accounts for > 85 % Faradaic efficiency at 5 % O₂. The development of a PTFE GDE architecture prevents all oxygen reduction on the carbon substrate and achieves 40.1 % Faradaic efficiency to C₂₊ at 350 mA/cm² with a 4 % O₂ impurity. Finally, stability measurements with NO or SO₂ were conducted at 100 mA/cm² and show that ∼200 ppm NO has a negligible influence on the performance, but ∼200 ppm SO₂ irreversibly shifts the product distribution from C₂₊ products to formate. This work comprises crucial information to potentially bypass the CO₂ purification steps, increasing economical viability.