Solar Hydrogen: DGIST Cuts Coating Voltage From 200 V to 4 V

Researchers in South Korea have found a cleaner way to make electrodes for solar hydrogen, cutting the voltage needed to coat them from 200 volts or more to just 4 volts. A team led by Professor Jongmin Choi of the Department of Energy Science and Engineering at DGIST, working with Professor Younghoon Kim’s team in the Department of Chemistry at Kookmin University, developed a water-based, low-voltage process that also raised photocurrent roughly tenfold.

The findings were published in Small, a materials science journal. Dr. Jin Young Park and PhD student Haejeong Kim of DGIST are co-first authors.

The problem with today’s solar hydrogen electrodes

Many systems that use sunlight to produce hydrogen rely on titanium dioxide (TiO2). It is very stable, but it absorbs only ultraviolet light, which limits efficiency.

To capture more of the spectrum, researchers have tried pairing titanium dioxide with silver- and bismuth-based nanomaterials. The catch is in manufacturing. Attaching these nanomaterials to an electrode has typically required 200 V or more and toxic organic solvents, which runs against the goal of environmentally friendly hydrogen production.

How DGIST cut the voltage to 4 V

The joint team took a two-step approach:

• Hydrophilic surfaces: They replaced the molecules on the surface of the nanocrystals with hydrophilic molecules that mix readily with water.
• Aqueous electrophoretic deposition: They then applied a low voltage in a water solution so the particles would stick to the electrode.

The result was a process voltage of just 4 V, which DGIST compares to the voltage of a battery. Coating took about three minutes in a safe aqueous solution with no toxic organic solvents. The low voltage also avoided the surface damage and oxidation byproducts that occur under high-voltage conditions.

Solar hydrogen performance results

According to DGIST, the new photoelectrode delivered:

• About a tenfold or greater increase in photocurrent under illumination compared with conventional single-material electrodes
• A photocurrent density of 3.0 mA/cm² under conditions similar to natural sunlight
• 65.1% of its initial performance retained after two hours of continuous light exposure
• Gas analysis confirming that hydrogen was produced

The materials exclude hazardous elements such as lead and cadmium, and the process sharply reduces the use of organic solvents and high voltages.

“The significance of this study lies in achieving high hydrogen production efficiency through a safe and clean water-based, low-voltage process, overcoming the limitations of conventional processes that relied on high voltages and toxic solvents,” Choi said. “This achievement will serve as an important foundation for accelerating the practical application of eco-friendly hydrogen production technology.”

What still needs work

The stability figure shows there is room to improve. Keeping 65.1% of performance after two hours is a lab result, and practical systems would need to run far longer. The release does not give a commercialization timeline. Still, a manufacturing route that is cleaner and simpler could matter as much as raw efficiency when it comes to scaling up.

The research was supported by the Nano and Material Technology Development Program of the Ministry of Science and ICT, the National Research Foundation of Korea and the Ministry’s InnoCORE Program.

As a writer, I like that this work fixes the manufacturing side of green hydrogen, not just the chemistry, because a clean fuel made with toxic solvents is a hard sell. For more hydrogen research, see our stories on UNIST’s organic tandem photocathode, KAIST’s ruthenium catalyst and Groningen’s protonic ceramic electrolyzer.

FAQ

What is solar hydrogen?

It is hydrogen produced using sunlight, here through a photoelectrode that absorbs light and drives the reaction that splits water to make hydrogen.

What did DGIST change?

The team made nanocrystal surfaces water-friendly so they could be deposited onto electrodes in water at 4 V, instead of 200 V or more with toxic organic solvents.

Does the new electrode use lead or cadmium?

No. DGIST says it uses silver- and bismuth-based nanomaterials and excludes hazardous substances such as lead and cadmium.