Rust can generate electricity when salt water flows over thin films of it, exciting new research has revealed, a result which holds potential for inventive new forms of sustainable power production.
Metal compounds and salt water often generate electricity, usually the result of a chemical reaction that changes at least one of the compounds into new compounds. Now scientists at Caltech and Northwestern University have found that rust, or iron oxide, converts the kinetic energy of flowing salt water into electricity.
“A similar effect has been seen in some other materials. You can take a drop of salt water and drag it across graphene and see some electricity generated,” Caltech professor Tom Miller said, explaining that while graphene films are difficult to fabricate and scale up, iron oxide is “basically just rust on iron, so it’s pretty easy to make in large areas.”
The team used physical vapor deposition (PVD), which turns normally solid materials into a vapor that condenses on a desired surface, to ensure that the rust formed in a consistent, thin layer. Incredibly, they were able to create a layer so fine that it’s around 10,000 times thinner than a human hair.
When salt water solutions flowed over this layer, the ions in the water attracted electrons in the iron under the layer of rust and dragged those electrons along with them, generating an electrical current. The process could be used in the future to generate energy on items like buoys floating in the ocean.