Fe-doped cobalt carbonate hydroxide nanowire array stabilized by chromium‑nickel hydroxide boosting electrochemical...

Seawater electrolysis as a route for green hydrogen production holds great promise in advancing carbon neutrality. However, chloride ions (Cl^-) in seawater can severely corrode catalytic active sites, significantly reducing system durability. Here, we report the synthesis of an Fe-CoOCH@CrNi(OH)_x catalyst, in which a protective layer is engineered via electrochemical methods. The process involves electrochemical pre-oxidation of Fe-doped cobalt carbonate hydroxide (Fe-CoCH) precursors followed by electrodeposition. Owing to its large active surface area and excellent catalytic activity, the electrode for oxygen evolution reaction (OER) achieves low overpotentials of 265 mV and 277 mV in alkaline freshwater and seawater, respectively, at a current density of 100 mA cm^-2. Moreover, with the protection of the CrNi(OH)_x layer, Fe-CoOCH@CrNi(OH)_x exhibits almost no activity decay at a current density of 100 mA cm^-2 in alkaline seawater over 30 h. This pre-oxidation-induced surface reconstruction combined with electrodeposited protection offers a new strategy for in-situ construction of advanced non-noble metal OER catalysts.