Sulfur‐Doped High‐Entropy Spinel Oxide (FeCoNiCuCrAlZn) ₃ O ₄ Electrocatalyst for Seawater Electrolysis

Natural seawater electrolysis represents a promising approach to green hydrogen production. However, it faces major challenges such as kinetically sluggish oxygen evolution reaction (OER) and competing chlorine evolution reaction. In this study, a sulfur(S)‐doped high entropy spinel ((FeCoNiCuCrAlZn) 3 O 4 ‐S) electrocatalyst was synthesized on nickel foam (NF) via a hydrothermal method as the anode for seawater splitting. The obtained (FeCoNiCuCrAlZn) 3 O 4 ‐S/NF electrode exhibited a low OER overpotential of 266 mV at 10 mA·cm −2 and maintained stable operation for over 200 h at a current density of 100 mA·cm −2 . When it was employed in an anion exchange membrane electrolyzer as the anode, a current density of 500 mA·cm −2 at a voltage of 2.3 V was achieved with a stable operation for over 40 h in 1.0 M KOH natural seawater, showing a great potential for achieving high‐efficiency and low‐cost seawater splitting. It is considered that the superior OER performance of (FeCoNiCuCrAlZn) 3 O 4 S is attributed to sulfur‐induced electronic structure reconfiguration, which boosts the intrinsic activity of active sites and accelerates reaction kinetics. This provides valuable insights for designing efficient and stable non‐noble metal electrocatalysts for seawater splitting.