Self-adaptive amorphous CoOxCly electrocatalyst for sustainable chlorine evolution in acidic brine

Electrochemical chlorine evolution reaction is of central importance in the chlor-alkali industry, but the chlorine evolution anode is largely limited by water oxidation side reaction and corrosion-induced performance decay in strong acids. Here we present an amorphous CoOxCly catalyst that has been deposited in situ in an acidic saline electrolyte containing Co2+ and Cl- ions to adapt to the given electrochemical condition and exhibits similar to 100% chlorine evolution selectivity with an overpotential of similar to 0.1 V at 10 mA cm(-2) and high stability over 500 h. In situ spectroscopic studies and theoretical calculations reveal that the electrochemical introduction of Cl- prevents the Co sites from charging to a higher oxidation state thus suppressing the O-O bond formation for oxygen evolution. Consequently, the chlorine evolution selectivity has been enhanced on the Cl-constrained Co-O* sites via the Volmer-Heyrovsky pathway. This study provides fundamental insights into how the reactant Cl- itself can work as a promoter toward enhancing chlorine evolution in acidic brine.

Automated summary

In this study, an amorphous CoOxCly catalyst was deposited in situ in an acidic saline electrolyte containing Co2+ and Cl- ions to enhance the selectivity and stability of chlorine evolution in the chlor-alkali industry. In situ spectroscopic studies and theoretical calculations revealed that Cl- acted as a promoter to enhance the chlorine evolution by preventing the higher oxidation state of Co sites, thus suppressing the oxygen evolution reaction.