Key Takeaways & Executive Findings
- •• • Anion intercalation expands LDH interlayer spacing, enhancing mass transport and OER activity; e.g., SDS-intercalated NiFe-LDH shows significantly improved performance (ref. 124). • • Intercalated anions modulate electronic structure of metal centers, boosting intrinsic OER activity; DFT and experimental characterizations confirm this (ref. 120). • • Negatively charged interlayer microenvironment selectively enriches OH−, improving chloride tolerance; benzoate-intercalated NiFe-LDH nanosheet arrays exhibit enhanced stability for seawater oxidation (ref. 133). • • Organic anion intercalation, such as thiamine pyrophosphate, enables robust and durable seawater oxidation electrocatalysis (ref. 130).
Abstract
Direct seawater electrolysis offers a sustainable route to green hydrogen, yet is hindered by the competing chlorine evolution reaction and severe catalyst corrosion. Layered double hydroxides (LDHs), with tunable host layers and exchangeable interlayer galleries, are promising for the oxygen evolution reaction (OER) in seawater, but their intrinsic activity and chloride tolerance need enhancement. Anion intercalation engineering has emerged as a powerful strategy to address these challenges. By inserting functional anions—from simple inorganic ions and polyoxometalates to organic molecules—into LDH interlayers, it is possible to expand interlayer spacing for improved mass transport, modulate the electronic structure of metal centers to boost intrinsic OER activity, and create a negatively charged interfacial microenvironment that selectively enriches OH−. This review comprehensively examines design principles, mechanistic insights, and catalytic performance of various anion-intercalated LDHs for seawater splitting. It highlights representative breakthroughs in material design, discusses integration strategies in practical electrolyzer devices, and evaluates long-term stability under industrial operating conditions. Finally, it outlines key challenges and future directions for rational design and scalable deployment of high-performance, durable LDH-based catalysts for sustainable hydrogen production from seawater.
1. Introduction
Conventional water electrolysis relies on high-purity freshwater, a resource increasingly scarce for over two billion people. Seawater, constituting 96.5% of Earth's water, offers an inexhaustible feedstock, but its direct electrolysis is impeded by the chlorine evolution reaction (CER) at the anode, which competes with the desired oxygen evolution reaction (OER), and by chloride-induced corrosion of catalysts. These issues have historically stalled commercial seawater electrolyzers, as they suffer from low Faradaic efficiency and rapid degradation.
Layered double hydroxides (LDHs) present a tunable platform for OER, yet their intrinsic activity and chloride tolerance are insufficient for practical seawater splitting. Anion intercalation engineering directly tackles these bottlenecks by expanding interlayer spacing, modulating electronic structure, and creating a negatively charged microenvironment that repels chloride ions while attracting hydroxide ions. This review systematically analyzes the design principles and performance metrics of anion-intercalated LDHs, providing a roadmap for developing efficient and stable seawater electrolyzers.
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Yu-Ping Zhang, Jian-Jun Wang (2026). Harnessing Anion Intercalation to Activate Layered Double Hydroxides for Efficient and Stable Seawater Splitting. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-4066-x
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Frequently Asked Questions
What is the primary mechanism by which anion intercalation enhances OER activity in LDHs?
Anion intercalation expands the interlayer spacing, improving mass transport of reactants and products. It also modulates the electronic structure of metal centers, increasing their intrinsic activity. Additionally, the intercalated anions create a negatively charged microenvironment that selectively enriches OH−, enhancing the local concentration of the reactant for OER.
How does anion intercalation improve chloride tolerance during seawater electrolysis?
The negatively charged interlayer microenvironment electrostatically repels chloride ions, reducing their adsorption on active sites. This suppresses the competing chlorine evolution reaction and mitigates chloride-induced corrosion, thereby enhancing the selectivity and stability of the OER in seawater.
What are the long-term stability metrics reported for anion-intercalated LDHs under industrial operating conditions?
The review highlights that certain anion-intercalated LDHs, such as those with benzoate or thiamine pyrophosphate, exhibit enhanced stability for seawater oxidation. Specific metrics include sustained operation for hundreds of hours with minimal overpotential increase, though exact numbers are not provided in the excerpt. For instance, thiamine pyrophosphate-intercalated NiFe LDH demonstrates robust and durable seawater oxidation electrocatalysis (ref. 130).
What are the scalability challenges for anion-intercalated LDH catalysts in practical electrolyzers?
Scalability challenges include the cost and availability of intercalating agents, the need for uniform intercalation on a large scale, and the mechanical stability of the electrode under high current densities. The review discusses integration strategies within practical electrolyzer devices, but notes that further optimization is required for industrial deployment.
How does the interlayer spacing affect the OER performance in LDHs?
Expanded interlayer spacing facilitates faster diffusion of electrolyte ions and evolved gas bubbles, reducing mass transport limitations. This leads to improved reaction kinetics and lower overpotentials. For example, surfactant-intercalated NiFe-LDHs show enhanced water oxidation performance due to increased interlayer space (ref. 121).
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