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Researchers at Nanyang Technological University, Singapore have built a solar-powered device that generates clean hydrogen from seawater while simultaneously breaking down hydrazine, a highly toxic pollutant found in industrial wastewater — accomplishing two environmental goals with a single piece of technology.
The device, described in a study published in Nature Communications in May and led by Prof. Lydia Wong of NTU's School of Materials Science and Engineering, is inspired by the way plant leaves capture sunlight. It converts light directly into electricity to drive its chemical reactions, requiring no external power source.
Hydrogen is typically produced through electrolysis, a process in which an electric current splits water molecules into hydrogen and oxygen. Using seawater instead of fresh water for this reaction is more sustainable, since it skips the energy-intensive step of desalination. But seawater brings its own complications: chloride ions interfere with the reaction and lower its efficiency, while the process also generates corrosive, toxic chlorine compounds that can damage the electrodes over time.
To get around these problems, Wong's team redesigned the device's anode to include a catalyst — made from iron, cobalt and chromium — that breaks down hydrazine into hydrogen and nitrogen instead of performing the standard oxygen-producing reaction. Because this reaction requires less energy, the sunlight-powered cathode can generate hydrogen more efficiently, while the anode simultaneously removes the toxic pollutant and produces additional hydrogen of its own. The chlorine-generating side reactions that normally plague seawater electrolysis are suppressed in the process. The catalyst is also resistant to corrosion and can be chemically and physically customized.
The device's light-capturing cathode is made from lead halide-based perovskites, a semiconductor material that absorbs light and converts it into electricity. It is coated with a conductive epoxy resin containing silver and copper particles, along with a titanium foil layer that protects it from degrading over time.
In tests using both simulated and real seawater, the device generated a stable electric current from light, reaching a photocurrent density of 25 milliamps per square centimeter — among the highest ever reported for a lead-based perovskite cathode. It maintained stable performance for more than 72 hours under illumination equivalent to full sunlight, producing hydrogen at a rate of 466 micromoles per square centimeter per hour, a figure the researchers say is comparable to similar solar-driven devices. Over 30 hours, it also reduced hydrazine concentration from 0.5 molar to just 0.5 parts per billion — more than 20 times below the U.S. Environmental Protection Agency's permissible limit of 10 parts per billion.
"This dual-function device represents a major leap forward for environmental technology," Wong said, noting that it tackles an energy problem and a pollution problem at the same time. Prof. James Durrant of the University of Oxford, who was not involved in the research, said the work demonstrates a practical route toward multifunctional solar fuel systems where economic and environmental value go hand in hand.
The NTU team is now working to expand the device's capabilities beyond hydrazine degradation, aiming to treat other pollutants and convert waste materials into useful fuels and industrial chemicals.
