Paired electrochemical synthesis of Cl2 from alkali chloride and CO from CO2

In order to bring electrochemical CO 2 reduction (eCO 2 R) to economical feasibility on an industrial scale, the conventional oxygen evolution reaction (OER) can be replaced with a value added reaction. In this work, we replace OER with chlorine evolution reaction (CER) in a paired synthesis with CO from CO 2 . Hereby, the reaction system is assessed at industrial relevant current densities with respect to electrolyte species & concentration and stability of up to 24 h. We report constant anodic FEs to Cl 2 of > 97 % for up to 400 mA / cm 2 with concurrent FEs to CO of 90 % at 100 mA / cm 2 and 74 % at 200 mA / cm 2 over 4.5 h, significantly exceeding previous studies for comparable systems. The FE for CER did not show any decline over 24 h of operation. KCl showed superior results over NaCl and CsCl in terms of cathodic FE and cell potential. CER is affected by educt limitation with FE dropping below 95 % at an electrolyte concentration of 0.8 mol/L at 400 mA / cm 2 . By successfully pairing eCO 2 R and CER with stable and high FEs at industrially relevant current densities, this work marks an important step towards an industrial application. • Paired electrochemical synthesis of Cl 2 from alkali chloride and CO from CO 2 . • Concurrent FE of > 97 % to Cl 2 and 75 % to CO at 200 mA / cm 2 . • Online analytics of anodic chlorine evolution with Faraday efficiency (FE) > 97 % at 400 mA / cm 2 . • KCl superior over NaCl and CsCl in terms of cathodic FE to CO and cell potential. • Anodic FE drops below 95 % as anolyte concentration falls below 0.8 mol/L at 400 mA / cm 2 .