Confining chlorine in the cation solvation sheaths towards stable and sustainable seawater electrolysis

Abstract

Abstract Chlorine electro-oxidation represents the primary anode side reaction during direct seawater electrolysis, causing corrosion and permanent deactivation of catalyst and thereby insufficient stability. We report that in situ segregated fluorine can actuate the desolvation of cations and Cl − ions via strong H ∙ ∙ ∙ F bonding, leading to the formation of intimate cation-Cl − contact ion pairs that make Cl − migration toward electrode surface prohibited. Meanwhile, fluorine remaining in the cobalt-based catalyst shortens the Co–Co distance, attributable to its large electronegativity, triggering an oxide path mechanism that circumvents the nonideal scaling between OH * and OOH * during oxygen-evolving reaction. Direct seawater electrolysis (with 1 M NaOH) incorporating this catalyst achieves 1 ampere per square centimeter (A cm −2 ) at 1.7 volts and maintains at 0.5 A cm −2 and 60 °C over 2,450 hours degrading at 24.9 microvolts per hour. Our catalyst even survives repeatedly switched current densities (0.25, 0.5, and 1 A cm −2 ) for more than 1,250 hours, manifesting compatibility with fluctuating renewable electricity.