Researchers from the Adelaide University have shown that green hydrogen can be produced reliably using cheaper, less-purified water, challenging the long-held assumption that ultra-pure water is always required.
The team, led by Professor Shi-Zhang Qiao, demonstrated that water treated by reverse osmosis, a common and low-cost purification method, can be used effectively for green hydrogen production.
Reverse osmosis is already widely used around the world to turn seawater into drinking water by pushing it through special membranes that remove most salts and impurities.
One reason ultra-pure water is normally required for hydrogen production is that even very small amounts of leftover salts can damage the equipment used to split water into hydrogen and oxygen. This has limited the use of more affordable water sources, such as reverse osmosis water, despite their availability and lower cost.
By adding a specially designed anode catalyst to a proton exchange membrane water electrolyser, the researchers showed that reverse osmosis purified water could be used without sacrificing durability. The new system achieved performance comparable to electrolysers operated with ultra-pure deionised water.
The findings were published in the journal Nature Catalysis.
Professor Qiao said that water purity has long been a hidden cost barrier for green hydrogen.
“Making green hydrogen usually requires extremely clean and expensive water to keep the system running reliably,” he said.
“In recent years, researchers have started looking at whether less-than-perfect water could be used instead. While directly using seawater remains technically challenging, reverse osmosis purification already provides large amounts of relatively clean water at much lower cost.
“Our work shows that, with the right catalyst design, this type of water can be used reliably in hydrogen-producing electrolysers.”
The research team found that the new anode catalyst helped protect the system from the small residual impurities left after reverse osmosis treatment, opening up new possibilities for practical hydrogen production.
“The cost of producing reverse osmosis water is only US$0.57 per tonne, which is far less than the US$9.11 per tonne for purified deionised water, which is generally used in this operation,” Professor Qiao said.
“In this study, the electrolyser achieved 2,000 hours of operation with no significant performance degradation when using reverse osmosis purified water.
“Together, the new impurity-tolerant electrolyser design could help make green hydrogen cheaper and easier to produce, both locally and at industrial scale, by reducing the need for ultra-pure water.”