CO-mediated organocatalytic chlorine evolution under industrial conditions.

During the chlor-alkali process, in operation since the nineteenth century, electrolysis of sodium chloride solutions generates chlorine and sodium hydroxide that are both important for chemical manufacturing. As the process is very energy intensive, with 4% of globally produced electricity (about 150 TWh) going to the chlor-alkali industry, even modest efficiency improvements can deliver substantial cost and energy savings. A particular focus in this regard is the demanding chlorine evolution reaction, for which the state-of-the-art electrocatalyst is still the dimensionally stable anode developed decades ago. New catalysts for the chlorine evolution reaction have been reported, but they still mainly consist of noble metal. Here we show that an organocatalyst with an amide functional group enables the chlorine evolution reaction; and that in the presence of CO, it achieves a current density of 10 kA m and a selectivity of 99.6% at an overpotential of only 89 mV and thus rivals the dimensionally stable anode. We find that reversible binding of CO to the amide nitrogen facilitates formation of a radical species that plays a critical role in Cl generation, and that might also prove useful in the context of Cl batteries and organic synthesis. Although organocatalysts are typically not considered promising for demanding electrochemical applications, this work demonstrates their broader potential and the opportunities they offer for developing industrially relevant new processes and exploring new electrochemical mechanisms.