The new method could be more efficient at generating energy than the best solar panels.
Scientists from Northwestern University and Caltech have produced electricity by flowing water over extremely thin layers of rust.
They say this is an entirely new way of generating electricity and could be used to develop new forms of sustainable power production.
Current is generated when pulses of rainwater and ocean water alternate and move across the nanolayers which are 10 to 20 nanometres thick – hundreds of times thinner than a plastic bag. The difference in salinity drags the electrons along in the metal below – “like dragging a magnet across a window”.
“It’s the oxide layer over the nanometal that really makes this device go,” said Franz M. Geiger, the Dow Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences. “Instead of corrosion, the presence of the oxides on the right metals leads to a mechanism that shuttles electrons.”
The process could be more efficient than solar panels, the researchers say, noting that the electrokinetic effect is around 30 per cent efficient at converting kinetic energy into electricity, compared to the best solar panels at about 20 per cent efficient.
When tested, the devices generated several tens of millivolts and several microamps per centimetre squared.
The process could be more efficient than solar panels.
“For perspective, plates having an area of 10 square metres each would generate a few kilowatts per hour – enough for a standard US home,” said Tom Miller, Caltech professor of chemistry, adding: “Of course, less demanding applications, including low-power devices in remote locations, are more promising in the near term.”
While a similar effect has been found with other materials, such as graphene and carbon nanotubes, the researchers claim their method is more scalable and cheaper due to a single-step fabrication process and the availability of materials.
"It’s basically just rust on iron, so it’s pretty easy to make in large areas," Miller says. "This is a more robust implementation of the thing seen in graphene."
The findings could be useful in specific scenarios where there are moving saline solutions, like in the ocean or even the human body.
"For example, tidal energy or things bobbing in the ocean, like buoys, could be used for passive electrical energy conversion," Miller said. "You have saltwater flowing in your veins in periodic pulses. That could be used to generate electricity for powering implants."
You have saltwater flowing in your veins in periodic pulses. That could be used to generate electricity for powering implants.
Northwestern has filed for a provisional patent.
Energy Conversion via Metal Nanolayers was published in the Proceedings of the National Academy of Sciences (PNAS) journal.
You might also like: