Joule-Heating-Driven Encapsulation of FeCo Nanoparticles in Ion-Selective Carbon Shell for Stable Seawater Electrolysis

The oxygen evolution reaction (OER) in seawater is notoriously hindered by slow kinetics and high overpotential, compounded by chloride-induced corrosion, which impedes efficient hydrogen production via seawater electrolysis. A key challenge is to devise an OER catalyst that not only mitigates chlorine oxidation and corrosion but is also cost-effective. In this work, the bimetallic iron-cobalt (FeCo) nanoparticles are swiftly encapsulated within N-doped carbon shells in mere seconds using the Joule-heating technique, a process significantly faster than the several hours required by traditional furnace heating. Meanwhile, the high temperature could offer the necessary activation energy for Fe/Co atom redispersion on the carbon shell via forming abundant metal-nitrogen (Co/Fe-N-C) active sites. These Co/Fe-N-C sites exhibit exceptional activity for OER catalysis. Consequently, the sample prepared by Joule-heating at 800 °C for 5 seconds (FeCo@CN-J-5) demonstrates superior OER performance, achieving a current density that is 35 times greater than that prepared without N doping and 6 times higher than that prepared via furnace heating. Moreover, FeCo@CN-J-5 operates stably for 100 hours at 200 mA cm-2 with negligible degradation in the highly corrosive electrolyte of 0.1 M KOH + 0.6 M NaCl, demonstrating its promising potential for practical seawater splitting.