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

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. © 2025 Wiley-VCH GmbH.