Hard Lewis acid CeO2 and Cl− intercalation induce OH− enriched and strong Cl− repulsive microenvironment for ultra-stable industrialized seawater electrolysis

Abstract

Direct electrolysis of seawater offers a transformative technology for sustainable hydrogen production, circumventing the constraint of freshwater scarcity. However, the serious electrode corrosion and competitive chloride oxidation reactions make oxygen evolution reaction (OER) in seawater extremely challenging. Herein, the low-cost and scalable CoFe layered double hydroxides with Cl⁻ intercalation and decorated with Ce(OH)₃ (named as CoFe-Cl⁻/Ce(OH)₃) catalyst is synthesized via rapid electrodeposition under ambient conditions, which is quickly reconstructed into a CeO₂ decorated and Cl⁻ intercalated CoFeOOH (CoFeOOH-Cl⁻/CeO₂) during OER. Theoretical investigation reveals that Cl⁻ intercalation weakens the adsorption ability of Cl⁻ on Co/Fe atoms and hinders unfavorable coupling with chloride, thereby preventing the chlorine corrosion process and enhancing catalytic stability and activity. The CeO₂ with hard Lewis acidity preferentially binds to OH⁻ with harder Lewis base to ensure the OH⁻ rich microenvironment around catalyst even under high current operating conditions, thus further enhancing stability and improving OER activity. The functionalized CoFe-Cl⁻/Ce(OH)₃ delivers 1000 mA cm⁻² current density at only 329 mV overpotential with excellent stability for 1000 h under alkaline seawater. Electrochemical experiments elucidate the OER catalytic mechanism in which CeO₂ serves as a co-catalyst for enriching OH⁻ and CoFeOOH-Cl⁻ is the active species. Our work is a substantial step towards achieving massive and sustainable production of hydrogen fuel from immense seawater.