Iron‐Cobalt Co‐Doped Nickel Sulfides: A Robust Electrocatalyst for High‐Current‐Density Seawater Splitting

Abstract Nickel–iron‐based sulfides have recently attracted considerable attention as promising candidates for water oxidation. However, the high concentration of chloride ions (Cl − ) in seawater poses a major challenge, as they readily corrode active sites and significantly compromise long‐term durability. Most nickel–iron‐based sulfides suffer from poor stability under these conditions, particularly at high current densities, which greatly hinders their practical application in large‐scale seawater electrolysis. In this study, an innovative iron and cobalt co‐doped nickel sulfide (NiFeCoS) electrode is introduced, produced via a simple fabrication method, which effectively protects the active sites from Cl − attack during alkaline seawater oxidation, even under high current densities. The NiFeCoS catalyst exhibits remarkable stability, maintaining stable performance for over 148 h at a current density of 1 A cm −2 in alkaline seawater electrolytes. In an alkaline electrolyte, it achieves low overpotentials of 261, 312, and 342 mV to reach current densities of 100, 500, and 1000 mA cm −2 . This research presents a novel approach for constructing NiFeCoS electrodes through a straightforward two‐step synthesis process, offering a promising and efficient strategy for large‐scale hydrogen production via seawater electrolysis.