An "artificial leaf" that produces hydrogen from indoor lighting—just as plants absorb sunlight to create energy—has been developed. Experts say this opens a pathway to recycle lighting electricity, which accounts for 19% of global power consumption, into clean hydrogen energy.
A research team led by Professor Jang Ji-hyun at UNIST's Department of Energy and Chemical Engineering announced on the 19th that they developed an artificial leaf that produces hydrogen from LED lighting by combining an efficient photoelectrode with a hydrogen production catalyst.
The core of the artificial leaf is the photoelectrode. Like chlorophyll in plants, the photoelectrode absorbs light to generate charge particles.
The photoelectrode developed by the research team is made of cadmium sulfide (CdS), a material that can absorb indoor lighting—which is weaker than sunlight—and generate charge particles. The produced charge particles pass through a titanium dioxide (TiO₂) layer and are transferred to a hydrogen production catalyst layer (3D nickel) on the back. When charge particles react with water on this catalyst layer surface, hydrogen is produced.
During the artificial leaf design process, the research team focused on achieving both stability and efficiency under indoor lighting conditions. Sulfide materials undergo "photocorrosion," where the material gradually degrades when exposed to strong light, but weak indoor lighting can minimize this. The team also designed an electrode structure with titanium dioxide bonded to the sulfide to compensate for reduced charge particles due to weak light. This enables limited charges to be fully used for hydrogen production without recombination losses. Additionally, by coating the sulfide surface with phosphate (Pi) as a protective layer, they prevented photocorrosion while increasing charge transfer speed.
Cost-performance is also excellent. The artificial leaf developed by the research team recorded a photocurrent of 119-120 microamperes (µA/cm²) using only indoor lighting without external voltage, maintaining 94% of initial performance after 12 hours. This is comparable to using expensive platinum (Pt) catalysts (121 µA/cm²). Photocurrent is typically used as an indicator to gauge hydrogen production in artificial leaves.
The 3D nickel used as a hydrogen production catalyst is inexpensive and can be printed like ink, making it easy to manufacture in required sizes for commercialization. The research team also fabricated a large module connecting four 85 cm² artificial leaves in series, which recorded a total photocurrent of 5 milliamperes (mA) under indoor lighting.
Professor Jang Ji-hyun explained, "Unlike solar power, which is sensitive to weather, indoor lighting has the advantage of being consistent," adding, "As this research confirmed that light wasted indoors can be used as an energy source for hydrogen production, we plan to complement hydrogen separation and recovery technologies going forward."
This research was supported by the ERC project of the "Microplastics Response Chemical and Bio Convergence Process Research Center," the Mid-career Research Program, and the Innokorea Project. Results were published online on the 16th of last month in the international journal "Applied Catalysis B: Environmental and Energy," with formal publication forthcoming.