Unlocking superior stability in high‑salinity oxygen evolution reaction: A Ru stabilized NiFeOOH/Ni anode with over 2000 h durability

As the demand for green hydrogen production continues to grow, the limitations of freshwater scarcity and anode corrosion in saline water electrolysis become more pronounced. Now, researchers from the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, led by Professor Yichao Lin, Professor Yayun Zhao, and Professor Liang Chen, have presented a breakthrough strategy for stabilizing NiFe-based anodes in highly corrosive chloride-rich environments. This work offers valuable insights into the development of next-generation anode materials that can overcome the durability challenges in saline water electrolysis.

Why This Dual Stabilization Strategy Matters

· Energy Sustainability: Saline water electrolysis enables hydrogen production from abundant seawater and salt lake resources, addressing the "freshwater scarcity" barrier in traditional water electrolysis.

· Industrial Viability: By achieving over 2000 hours of stable operation at industrial current densities, this strategy overcomes the "durability wall" that has limited commercial deployment of saline water electrolysis.

· Green Hydrogen Economy: Mimicking the chlor-alkali industry's use of ruthenium, this approach enables corrosion-resistant anodes essential for scaling up carbon-free hydrogen production.

Innovative Design and Features

· Dual-Function Stabilizing Agent: Ruthenium incorporation serves dual roles—promoting formation of a protective Ru-enriched surface layer at the catalyst-substrate interface, and atomically dispersed Ru (RuSA) within the NiFeOOH matrix to shield active sites from chloride attack.

· Functional Materials: The selection of ruthenium ions is crucial for achieving both structural protection and electronic modulation. Ion transport dynamics, phase reconstruction behavior, and interfacial engineering are discussed as key components for anti-corrosion anode design.

· Structural Characteristics: The RuSA-NiFeOOH/Ni features a dense nanosheet morphology with crack-free structure, contrasting with the rod-dominated morphology of conventional NiFeOOH/Ni. Cross-sectional analysis reveals Ru concentration at the catalyst-Ni foam interface forming a protective barrier.

Mechanistic Insights and Performance

· Exceptional Durability: The RuSA-NiFeOOH/Ni anode exhibits operational stability exceeding 2000 hours at 0.5 A cm−2 in chloride-enriched alkaline medium (1 M KOH + 2 M NaCl), whereas state-of-the-art NiFe-LDH/Ni and NiFeOOH/Ni anodes fail within 15 hours under identical conditions.

· Enhanced Catalytic Activity: The optimized anode demonstrates an ultralow overpotential of 220 mV at 100 mA cm−2 in simulated saline water (1 M KOH + 0.5 M NaCl), with fast OER kinetics indicated by a Tafel slope of 37.12 mV dec−1.

· Structural Evolution: In situ vibrational spectroscopy and electrochemical analysis reveal that Ru promotes irreversible oxidation of Ni2+ to Ni3+, leading to formation of a robust and compact catalyst layer that effectively blocks chloride penetration toward the substrate.

· Electrostatic Protection: Atomically dispersed Ru creates a localized chloride-enriched region around Ru sites, which electrostatically repels chloride ions and thereby shields adjacent catalytic sites (Ni/Fe) from corrosive attack.

Applications and Future Outlook

· Industrial Electrolyzer Integration: The RuSA-NiFeOOH/Ni anode, paired with commercial Pt/Ni cathode, achieves stable operation for over 500 hours in a custom alkaline electrolyzer using highly concentrated alkaline saline electrolyte (6 M KOH + saturated NaCl) at 55°C.

· Real Seawater Compatibility: The system maintains stable operation for at least 500 hours in alkaline seawater (6 M KOH + natural seawater from Ningbo Beilun coast) with minimal degradation, confirming practical applicability.

· Scalable Fabrication: The synthesis is readily scalable—a uniform electrode measuring 35×35 cm2 was successfully fabricated, underscoring strong potential for commercialization of saline water electrolysis.

· Challenges and Opportunities: The study highlights the need for optimizing synthesis routes and exploring non-precious metal dopants to achieve similar dual stabilization effects while reducing cost. Future research will focus on translating this atomic-level protection strategy to earth-abundant catalyst systems.

This comprehensive study establishes a robust dual stabilization strategy that significantly enhances anode stability in saline water electrolysis. It highlights the importance of interdisciplinary research in materials science, electrochemistry, and chemical engineering to drive innovation in green hydrogen production. Stay tuned for more groundbreaking work from Professor Yichao Lin, Professor Yayun Zhao, and Professor Liang Chen at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences!

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