“Eliminating hazardous substances and boosting efficiency tenfold”: DGIST develops eco-friendly solar hydrogen production technology

□ A research team led by Professor Jongmin Choi of the Department of Energy Science & Engineering at DGIST (President Kunwoo Lee), in collaboration with a team led by Professor Younghoon Kim of the Department of Chemistry at Kookmin University, has developed a highly efficient photoelectrode that produces hydrogen using sunlight through a water-based, low-voltage process.

□ Technologies that produce hydrogen—a clean energy source—using sunlight primarily employ titanium dioxide (TiO₂). Although highly stable, titanium dioxide has limited efficiency because it can absorb only ultraviolet light. To overcome this limitation, researchers have been exploring ways to combine it with silver- and bismuth-based nanomaterials that absorb a broader spectrum of light. However, conventional methods require high voltages of 200 volts (V) or more and toxic organic solvents to attach these materials to electrodes, posing a problem that runs counter to the original goal of “environmentally friendly hydrogen production.”

□ The joint research team completely resolved this problem by replacing the molecules on the surfaces of nanocrystals with “hydrophilic molecules” that mix readily with water, and then introducing the “aqueous electrophoretic deposition” process in which a low voltage is applied in an aqueous solution to induce the adherence of particles to the electrode.

□ Consequently, the team dramatically reduced the process voltage from the previous 200 V to merely 4 V, comparable to the voltage of a battery. Additionally, the researchers successfully coated the electrode with the material in just three minutes in a safe aqueous solution, without using toxic organic solvents, completely eliminating the problems of surface damage and impurity (oxidation byproduct) formation that occurred under high-voltage conditions.

□ The newly developed photoelectrode exhibited an approximately tenfold, or greater, increase in photocurrent under illumination compared with conventional single-material electrodes. In experiments conducted under conditions similar to natural sunlight, it achieved an excellent photocurrent density of 3.0 milliamperes per square centimeter (mA/cm²). It consistently retained 65.1% of its initial performance after two hours of continuous light exposure, while gas analysis confirmed that hydrogen was successfully produced.

□ This achievement is expected to make a significant contribution to the commercialization of truly “eco-friendly green hydrogen” production, as it uses materials that completely exclude hazardous substances such as lead and cadmium while substantially reducing the use of organic solvents and reliance on high voltages during the deposition process.

□ “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,” said Professor Jongmin Choi of DGIST’s Department of Energy Science & Engineering. “This achievement will serve as an important foundation for accelerating the practical application of eco-friendly hydrogen production technology.”

□ This research was supported by the Nano & Material Technology Development Program of the Ministry of Science and ICT and the National Research Foundation of Korea, as well as the InnoCORE Program of the Ministry of Science and ICT. The findings were published in Small, a prestigious international journal in materials science, with Dr. Jin Young Park and Ph.D. student Haejeong Kim of DGIST participating as co-first authors.