Scientists Set Efficiency Record for Making Hydrogen From Sunlight
ULSAN, Oct. 27 (Korea Bizwire) — South Korean researchers have developed a solar-powered device that produces hydrogen directly from water without an external electricity supply, achieving what they say is a world-record efficiency for its class of organic semiconductor technology.
The research team at the Ulsan National Institute of Science and Technology, or UNIST, reported Monday that its new tandem photoelectrode converted 7.9% of incoming solar energy into hydrogen, a significant advance in efforts to develop cheaper methods of producing the clean-burning fuel.
Green hydrogen, produced by splitting water into hydrogen and oxygen using renewable energy, is considered a potential alternative to fossil fuels in industries seeking to reduce carbon emissions. But producing it economically remains a major technological challenge.
Conventional organic semiconductor photoelectrodes have struggled to generate enough voltage from sunlight alone to split water, requiring additional electricity.
The UNIST researchers addressed that limitation by stacking two organic semiconductor layers that absorb different wavelengths of sunlight, generating sufficient combined voltage to drive the reaction.
A key innovation was a connecting layer made from molybdenum oxide and an organic molecule known as 2PACz.
Unlike conventional connecting materials, which can absorb moisture and damage adjacent semiconductor layers, the new combination resists corrosion, reduces electronic defects and improves charge transfer.
In laboratory tests, a photoelectrode measuring just 0.56 square centimeters achieved a solar-to-hydrogen conversion efficiency of 7.9% without external voltage, the highest reported for an organic semiconductor-based photocathode operating under those conditions, according to the researchers.
The device also retained 86% of its initial photocurrent after 10 hours of operation, compared with 36% for a device using a conventional connecting material.
To demonstrate the technology beyond the laboratory, the researchers built a larger 320-square-centimeter module and successfully produced hydrogen outdoors using natural sunlight without an external power supply.
An economic assessment estimated that a facility producing 10 metric tons of hydrogen daily could achieve a production cost of $9.26 per kilogram at the technology’s current efficiency.
The researchers said the relatively low manufacturing cost of solution-processable organic semiconductors could help offset their lower conversion efficiency, making production costs comparable to those of some 10%-efficient photoelectrode systems.
Kim Jin-young, a professor at UNIST’s Graduate School of Carbon Neutrality, said the work addressed longstanding instability and corrosion problems in the connecting layers of stacked organic semiconductors.
The researchers hope the technology will eventually help lower the cost of green hydrogen production, although further improvements in efficiency, durability and scale will be needed before commercial deployment.
The study, supported by the National Research Foundation of Korea and UNIST, was published online Sept. 6 in the journal Applied Catalysis B: Environmental and Energy.
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Scientists Set Efficiency Record for Making Hydrogen From Sunlight, source
