Key Takeaways & Executive Findings
- •• • RuCr-Ni3P achieves >4000 h operational stability under industrially relevant conditions (likely >200 mA cm−2), addressing the critical durability bottleneck for seawater electrolysis anodes. • • Cl− ions are selectively captured by Ru sites, forming a dynamic Ru–Cl coordination motif that electronically modulates adjacent Ni centers, promoting high-valent Ni>3+ species and switching the OER pathway from LOM to AEM, enhancing intrinsic activity. • • Cr sites act as Lewis acid centers, promoting Cr–OH formation and creating a localized alkaline microenvironment that further boosts OER kinetics on high-valent Ni centers. • • The dual-site synergistic mechanism (Ru for Cl− regulation, Ni/Cr for catalysis) effectively converts Cl− from a performance-limiting species into a chemical switch, simultaneously improving activity and stability, offering a new design paradigm for direct seawater electrolysis.
Abstract
Direct seawater electrolysis offers a promising route to green hydrogen production, circumventing freshwater scarcity. However, the presence of chloride ions (Cl−) poses severe challenges, including competing chlorine evolution reaction (CER) and corrosion of anode catalysts. Here, we report a dual-atom catalyst design, RuCr-Ni3P, where Ru atoms with strong chloride affinity and Cr atoms as Lewis acid centers are co-doped into a nickel phosphide matrix. This catalyst exhibits outstanding oxygen evolution reaction (OER) activity and selectivity in alkaline seawater, achieving stable operation for over 4000 hours at industrially relevant current densities. Mechanistic studies reveal that Cl− ions are selectively captured by Ru sites, forming a dynamic Ru–Cl coordination motif that electronically modulates adjacent Ni centers, promoting the formation of high-valent Ni>3+ species. This switches the OER pathway from the lattice oxygen mechanism (LOM) to the more efficient adsorbate evolution mechanism (AEM). Concurrently, Cr sites facilitate the formation of Cr–OH species, creating a localized alkaline microenvironment that further enhances OER kinetics. This dual-site synergistic mechanism transforms Cl− from a detrimental impurity into a beneficial chemical switch, concurrently enhancing both activity and stability. Our findings provide a paradigm shift in seawater electrolysis catalyst design, turning a longstanding challenge into an opportunity for efficient and durable hydrogen production.
1. Introduction
Direct seawater electrolysis for hydrogen production is a cornerstone of the sustainable energy transition, yet its commercial deployment is hindered by the aggressive chloride environment at the anode. The competing chlorine evolution reaction (CER) and chloride-induced corrosion of conventional catalysts lead to poor selectivity and rapid degradation, limiting operational lifetimes to a few hundred hours under practical current densities. Prior mitigation strategies, such as physical barriers or protective overlayers, have proven insufficient, as they either impede mass transport or lack long-term stability under high-voltage operation.
Here, we introduce a fundamentally different approach: instead of excluding Cl−, we exploit its presence through rational catalyst design. By co-doping Ru and Cr into a nickel phosphide matrix, we create dual active sites that cooperatively harness Cl− to enhance OER performance. Ru sites selectively bind Cl−, forming a dynamic coordination motif that electronically tunes neighboring Ni centers, promoting high-valent Ni species and switching the reaction mechanism to a more efficient pathway. Simultaneously, Cr sites generate a localized alkaline microenvironment, further accelerating OER. This synergistic design transforms Cl− from a poison into a beneficial regulator, achieving exceptional stability exceeding 4000 hours and high activity, directly addressing the critical bottlenecks of seawater electrolysis.
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Guiping Zheng, Zijian Li, Shizheng Zhou, Haeseong Jang, Min Gyu Kim, Qing Qin, Liqiang Hou, Xien Liu (2026). Cl−-Driven Pathway Switching Enables Efficient Industrial-Current Seawater Oxidation on Dual-Atom Catalysts. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4153-2
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Frequently Asked Questions
What is the specific role of Ru in the RuCr-Ni3P catalyst, and how does it interact with chloride ions to enhance OER?
Ru sites possess strong chloride affinity, selectively capturing Cl− ions to form a dynamic Ru–Cl coordination motif. This interaction electronically modulates adjacent Ni active centers, promoting the formation of high-valent Ni>3+ species. This electronic modulation switches the OER pathway from the lattice oxygen mechanism (LOM) to the more efficient adsorbate evolution mechanism (AEM), thereby enhancing intrinsic activity.
How does the presence of Cr contribute to the catalyst's performance in alkaline seawater?
Cr acts as a Lewis acid center, promoting the formation of Cr–OH species on the catalyst surface. These Cr–OH species cooperatively create a localized alkaline microenvironment favorable for OER on the high-valent Ni centers. This synergistic effect enhances the overall OER kinetics and stability.
What is the significance of the >4000 h operational stability, and what current density was used?
The >4000 h stability is a critical milestone for industrial application, as it demonstrates the catalyst's resistance to chloride-induced corrosion and structural degradation under prolonged operation. While the exact current density is not specified in the provided text, it is described as 'industrially relevant conditions,' typically implying current densities in the range of 200–1000 mA cm−2. This longevity addresses a major bottleneck for commercial seawater electrolyzers.
How does the Cl−-driven pathway switching from LOM to AEM improve OER efficiency?
The LOM involves direct participation of lattice oxygen, which can lead to structural instability and dissolution. In contrast, the AEM proceeds via adsorbate evolution on metal sites, which is generally more kinetically favorable and less destructive to the catalyst lattice. By switching to AEM, the catalyst achieves higher OER activity and stability, as evidenced by the enhanced performance and long-term durability.
What are the potential scalability challenges for RuCr-Ni3P in industrial seawater electrolyzers?
Scalability challenges include the cost and scarcity of Ru, which is a precious metal. However, the dual-atom doping strategy minimizes Ru loading while maximizing its utilization. Additionally, the synthesis method needs to be cost-effective and reproducible for large-scale production. The catalyst's stability and performance under industrial conditions suggest it is a promising candidate, but further techno-economic analysis and scale-up studies are required.
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