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

Abstract

In order to bring electrochemical CO₂ reduction (eCO₂R) 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 CO₂. 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 Cl₂ of $>$97$\text{\%}$ for up to 400 $\mathrm{mA}/{\mathrm{cm}}^2$ with concurrent FEs to CO of 90$\text{\%}$ at 100 $\mathrm{mA}/{\mathrm{cm}}^2$ and 74$\text{\%}$ at 200 $\mathrm{mA}/{\mathrm{cm}}^2$ 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$\text{\%}$ at an electrolyte concentration of 0.8 mol/L at 400 $\mathrm{mA}/{\mathrm{cm}}^2$. By successfully pairing eCO₂R and CER with stable and high FEs at industrially relevant current densities, this work marks an important step towards an industrial application.