Improved Activity and Corrosion Resistance in Seawater Oxidation: Harnessing the Synergy between the Phosphide Layer and Nickel–Iron Hydroxide

Developing high-performance and cost-effective electrocatalysts for seawater oxidation is highly desirable yet remains a significant challenge. Herein, Fe-doped Ni(OH)2 with a Ni5P4 protective layer anchored on nickel foam (Fe–Ni(OH)2@Ni5P4/NF) has been successfully synthesized by partial phosphorization of nickel–iron-layered double hydroxide (LDH). The as-constructed catalyst exhibits low oxygen evolution reaction (OER) overpotentials of 260 and 265 mV at a current density of 100 mA cm–2 in alkaline water and seawater, respectively, as well as long-term durability at a high current density of 500 mA cm–2 for over 200 h toward seawater oxidation. More impressively, the Fe–Ni(OH)2@Ni5P4/NF(+)||Pt/C/NF(−) electrolyzer also exhibits an outstanding performance for overall seawater electrolysis, with a low cell voltage of 1.70 V at 100 mA cm–2 and operating steadily at 200 mA cm–2 for 100 h, outperforming the commercial RuO2/NF(+)||Pt/C/NF(−) (1.82 V at 100 mA cm–2) and most reported advanced electrocatalysts. Theoretical calculations reveal that an interfacial electronic redistribution induces a downshift of the Ni d-band center, effectively weakening *O intermediate adsorption and reducing the energy barrier for the rate-limiting *O→*OOH transition. The desirable activity and corrosion resistance of the Fe–Ni(OH)2@Ni5P4/NF catalyst could be attributed to the plentiful exposed active sites, the interfacial interactions between hydroxides and phosphides, and a negatively charged PO43– anionic layer. This work provides a universal strategy for designing robust heterostructured electrocatalysts through interface engineering.