Hainan University Team Breaks New Ground: Direct Seawater Electrolysis for Hydrogen Production and Magnesium Extraction

From “Scale Buildup” to Resource Recovery: A Dual-Benefit Innovation

Conventional electrolysis for hydrogen production relies heavily on high-purity freshwater. Using seawater directly has long been a challenge because its complex ionic composition—especially the high concentration of magnesium and calcium ions—can severely damage electrolysis equipment.

“It’s like the scale that builds up in a kettle over time,” explains Feng Suyang, a member of the research team. “In seawater electrolysis, the fouling happens much faster. Magnesium ions rapidly form precipitates on the electrode surface, causing it to deactivate in just a few hours.”

To overcome this issue, mainstream industry solutions typically involve desalinating seawater before electrolysis—an approach that adds significant process complexity and capital costs, keeping green hydrogen expensive.

But the team at Hainan University asked a different question:

“Instead of removing magnesium ions, why not collect them?”

A New Electrode Design Turns Waste into Value

Led by Professor Tian Xinlong, the research group recognized that the magnesium hydroxide precipitate accumulating on electrodes could be a valuable resource. Magnesium reserves in seawater are tens of thousands of times greater than on land, and magnesium hydroxide is a key raw material for flame retardants and aerospace applications.

The challenge was to cause magnesium ions to precipitate without sticking to the electrode surface.

After four years of research, the team developed a novel electrode material.

By introducing specific iodide ions onto the platinum electrode surface, they created an electrostatic repulsion effect—essentially giving the electrode a “protective shield.”

“The magnesium hydroxide produced during electrolysis can no longer adhere to the electrode,” says Feng Suyang. “Instead, it falls away in flocculent form and settles out as a precipitate.”

One Process, Two Products: Hydrogen + High-Purity Magnesium

The results go beyond technical feasibility.

In the laboratory, bottles of white powder—purified magnesium hydroxide with a purity exceeding 99%—demonstrate the output of the process.

“Previously, producing one kilogram of hydrogen came with a significant processing cost,” notes Professor Tian. “With this new approach, for every kilogram of hydrogen produced, we can theoretically co-generate about 15 kilograms of high-purity magnesium hydroxide. The value of the magnesium product can largely cover the cost of hydrogen production.”

Importantly, the technology operates in natural seawater at ambient temperature, significantly lowering the barriers for real-world deployment.

Scaling Up and Looking Ahead

From tiny one-square-centimeter electrodes to current 900-square-centimeter units, the team is steadily advancing toward larger-scale prototypes at Hainan University’s Collaborative Innovation Center.

Their vision is to integrate the technology with offshore wind power, enabling direct seawater electrolysis using renewable energy.

The green hydrogen produced could be used to synthesize green methanol, providing clean fuel for ocean-going vessels at ports like Yangpu.

The co-generated high-purity magnesium hydroxide could serve high-end new material supply chains, from specialty chemicals to lightweight alloys.

Source: People’s Daily (March 9, 2026, Page 14)

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