Seawater Electrolysis for Hydrogen Production

Seawater electrolysis offers a sustainable pathway to green hydrogen by utilising the planet’s most abundant electrolyte. Unlike freshwater splitting, direct seawater electrolysis must overcome chloride-driven corrosion, competing chlorine evolution, and precipitation of magnesium and calcium compounds at electrodes. Advances in membrane design, electrode architecture and electrocatalyst formulation have mitigated many of these challenges, enabling efficient separation of oxygen and hydrogen while preserving catalyst integrity. Anion-exchange and pH-asymmetric electrolysers exploit tailored ion transport to prevent chloride crossover and reduce energy consumption. Novel catalyst surfaces repel harmful ions or harness their adsorption to enhance oxygen evolution reaction rates. At the cathode, three-dimensional structures promote bubble detachment and inhibit scale formation. Combined with renewable electricity sources and integrated desalination schemes, seawater electrolysis promises cost-competitive hydrogen for maritime fuelling, remote islands and large-scale energy storage, transforming the global hydrogen economy.

Research from Nature Portfolio

A corrosion-resistant RuMoNi electrocatalyst has been developed for alkaline seawater electrolysis in an anion-exchange membrane electrolyser. In situ formation of molybdate species repels chloride ions, enabling stable operation at 500 mA cm⁻² for over 3 000 hours and achieving 77.9 % energy conversion efficiency at 1 000 mA cm⁻² and 1.72 V. The system meets US Department of Energy targets for hydrogen cost.

A pH-asymmetric electrolyser incorporating a Na⁺ exchange membrane prevents Cl⁻ corrosion and Ca²⁺/Mg²⁺ precipitation by exploiting chemical potential differences between acidified and alkalinised streams. Atomically dispersed Pt on Ni–Fe–P nanowires lowers the energy barrier for hydrogen evolution, achieving 100 mA cm⁻² at 1.46 V and 400 mA cm⁻² at 1.66 V (80 °C), with electricity costs below US$1.40 kg⁻¹ H₂.

A microscopic bubble/precipitate traffic system (MBPTS) built into honeycomb-type three-dimensional cathodes ensures uniform release of hydrogen bubbles to dislodge Mg²⁺/Ca²⁺ scales. This design delivers 1 A cm⁻² stable operation for 1 000 hours in alkaline seawater and near-100 % Faradaic efficiency at 500 mA cm⁻² for 150 hours, with estimated hydrogen costs under US$1.80 kg⁻¹.

Seawater Electrolysis for Hydrogen Production publication trend

The graph below shows the total number of articles in seawater electrolysis for hydrogen production across all publications each year (not limited to Nature Index journals).

Technical terms

Electrocatalyst: A material that lowers the energy barrier for electrochemical reactions at an electrode surface, improving rate and selectivity.

Oxygen Evolution Reaction (OER): The anodic half-reaction in water splitting, producing oxygen gas through multi-electron transfer steps.

Hydrogen Evolution Reaction (HER): The cathodic half-reaction in water splitting, generating hydrogen gas via proton reduction.

Anion-Exchange Membrane (AEM): A polymer membrane that selectively transports anions, preventing crossover of undesired species.

Faradaic Efficiency: The ratio of charge used for the desired electrochemical reaction to the total charge passed, indicating selectivity.

References

1. Sustainability assessment of seawater splitting: Prospects, challenges, and future directions. EcoEnergy (2024).
2. A corrosion-resistant RuMoNi catalyst for efficient and long-lasting seawater oxidation and anion exchange membrane electrolyzer. Nature Communications (2023).
3. High‐Performance Alkaline Seawater Electrolysis with Anomalous Chloride Promoted Oxygen Evolution Reaction. Angewandte Chemie International Edition (2023).
4. A sodium-ion-conducted asymmetric electrolyzer to lower the operation voltage for direct seawater electrolysis. Nature Communications (2023).
5. Efficient bubble/precipitate traffic enables stable seawater reduction electrocatalysis at industrial-level current densities. Nature Communications (2024).
6. Recent advances in non-noble metal-based bifunctional electrocatalysts for overall seawater splitting. Journal of Alloys and Compounds (2022).