Ultra-thin layers of rust generate electricity

Rust is a common blight on infrastructure. However, when combined with salt water, it can generate electricity, as new research shows.

Thin films of rust, or iron oxide, can generate electricity when saltwater flows over them, representing an entirely new form of sustainable power production. These are the findings of new research conducted by scientists at Caltech and Northwestern University.

While interactions between metal compounds and saltwater often generate electricity, this is usually the result of a chemical reaction in which one or more compounds are converted to new compounds. Reactions like these are used inside batteries, explains a statement.

The new phenomenon, known as the electrokinetic effect, does not involve chemical reactions. Instead, it converts the kinetic energy of flowing saltwater into electricity. It is around 30 per cent efficient, compared to the best solar panels at only about 20 per cent, according to the statement.

“A similar effect has been seen in some other materials. You can take a drop of saltwater and drag it across graphene and see some electricity generated,” commented Professor Tom Miller of Caltech. However, he added, it is difficult to scale graphene films up to usable sizes. By contrast, the iron oxide films are relatively easy to produce and scalable to larger sizes.

The mechanism behind the electricity generation involves ion adsorption and desorption. However, as the statement explains, “the ions present in saltwater attract electrons in the iron beneath the layer of rust. As the saltwater flows, so do those ions, and through that attractive force, they drag the electrons in the iron along with them, generating an electrical current.”

Photo credit: Natasha Wheatland/ CC BY-NC-ND 2.0

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