Self-Inhibiting Corrosion Protection through Dynamic Oxyanion Interfacial Regulation for Industrial Seawater Electrolysis

Direct seawater electrolysis offers a sustainable pathway for large-scale hydrogen production but is fundamentally challenged by chloride-induced corrosion, which rapidly destroys conventional transition-metal electrodes (Ni, Fe, Co, Cu, etc.) within 10 h. Herein, we report a self-inhibiting corrosion protection strategy enabled by a Ni-Fe-Cr-Mo superalloy (Hastelloy C-276) for durable alkaline simulated seawater electrolysis. When combined with the NiFe catalyst, the C-276 alloy substrate significantly improves electrode durability. Under a current density of 1.0 A cm-2, the NiFe/C-276 electrode achieves stable operation over a cumulative testing period of more than 10,800 h in alkaline simulated seawater. Integrated into an anion-exchange membrane (AEM) electrolyzer, the system delivers a current density of 5.0 A cm-2 at 2.01 V and maintains stable operation for over 500 h at 500 mA cm-2. Under the same operating current density, an OER Faradaic efficiency of 99.1% is achieved, with strongly suppressed formation of chlorine-derived byproducts. Detailed characterizations reveal that under anodic conditions, Hastelloy C-276 provides a sustained source of Mo- and Cr-derived oxyanionic species, which accumulate at the positively polarized NiFe oxyhydroxide interface. TOF-SIMS analysis and theoretical calculations further indicate that the resulting oxyanion-enriched interface suppresses chloride adsorption while optimizing the adsorption energetics of OER intermediates. The C-276 substrate therefore functions not only as a corrosion-resistant support but also as a reservoir that sustains interfacial oxyanion regulation during long-term operation. Distinct from conventional passive protection strategies, this work proposes a universal approach for integrating corrosion-resistant substrates with catalytic activity, providing a general framework for designing durable electrochemical systems operating in highly corrosive environments.