Mo-Mediated Dynamic Fe–Ni Nitride Heterointerfaces for Stable Ampere-Level Direct Seawater Electrolysis

Achieving stable ampere-level direct seawater electrolysis critically requires electrocatalysts capable of simultaneously resisting chloride-induced corrosion and suppressing the competing chlorine evolution reaction. Here, we report a nitrogen-rich, Fe-modified, and Mo-mediated Fe3N/Ni3N/MoOx heterostructured catalyst constructed in situ on a nickel foam, which enables efficient and durable alkaline freshwater and seawater electrolysis at ampere-level current densities. The coordinated Fe/Ni–N bonding and Mo-mediated interfacial coupling synergistically regulate the interfacial electronic structure, accelerating charge transfer while suppressing chloride adsorption and catalyst degradation. Operando Raman spectroscopy, operando X-ray photoelectron spectroscopy, and density functional theory calculations reveal that Fe incorporation and Mo mediation induce dynamic structural reorganization and multilevel heterointerface formation (Fe3N/MoO2 and Ni3N/MoO2), which collectively optimize water adsorption and dissociation, modulate hydrogen/oxygen-intermediate binding, and facilitate interfacial proton–electron transfer. Benefiting from this cooperative electronic and structural regulation, the catalyst delivers OER current densities of 1000 mA cm–2 at low overpotentials of 303 and 347 mV in alkaline freshwater and seawater, respectively, together with ultrahigh HER current densities of 2850 and 2420 mA cm–2 at 100 mV. When assembled into a two-electrode electrolyzer, the Fe3N/Ni3N/MoOx catalyst requires only low cell voltages of 1.577/1.602 and 1.617/1.656 V to achieve 500 and 1000 mA cm–2 in alkaline freshwater/seawater, respectively, and maintains stable operation for over 130 h at 500 mA cm–2 in alkaline seawater. This work establishes Fe-modified, Mo-mediated nitrogen-rich heterointerfaces as a powerful and generalizable strategy for developing non-noble, corrosion-resistant electrocatalysts toward practical large-current-density seawater electrolysis.