MIT Engineers Discovered a New Way of Generating Electricity

MIT engineers have discovered a new way to generate electricity by using carbon particles that are able to create an electric current through interaction with an organic solvent.

A material that constitutes carbon nanotubes is able to generate electricity by collecting energy from its environment. The liquid which is an organic solvent draws electrons out of the particles, generating a current that could be used to drive chemical reactions or to power micro- or nanoscale robots, the researchers say.

“This mechanism is new, and this way of generating energy is completely new,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT. “This technology is intriguing because all you have to do is flow a solvent through a bed of these particles. This allows you to do electrochemistry, but with no wires.”

In a new study describing this discovery, the researchers demonstrated that they could use this electric current to drive a reaction known as alcohol oxidation, an organic chemical reaction. Michael Strano is the senior author of the paper, which appeared in Nature Communications on June 7, 2021 The lead authors of the study are MIT graduate student Albert Tianxiang Liu and former MIT researcher Yuichiro Kunai. Other authors include former graduate student Anton Cottrill, postdocs Amir Kaplan and Hyunah Kim, graduate student Ge Zhang, and recent MIT graduates Rafid Mollah and Yannick Eatmon.

This new phenomenon resulted from Strano's research on carbon nanotubes. Back in 2010, Strano showed for the first time that carbon nanotubes can generate “thermopower waves.” If a carbon nanotube is coated with a layer of fuel thermopower waves travel in the tube, thus, creating an electric current.

This work caused Strano and his students to discover an unknown feature of carbon nanotubes. They discovered that when part of a nanotube is coated with a Teflon-like polymer, it results in an asymmetry that makes it possible for electrons to flow from the coated to the uncoated part of the tube, producing an electrical current. Electrons can be drawn out by immersing the particles in a solvent that is in need of electrons.

In order to utilize this capability, the researchers created electricity-generating particles by grinding up carbon nanotubes and forming them into a sheet of paper-like material. One side of each sheet was coated with a Teflon-like polymer, and the researchers then cut out small particles from the sheet. For this study, they made particles that were in the size of 250 microns by 250 microns.

When these particles are immersed in an organic solvent, the solvent adheres to the uncoated surface of the particles and begins pulling electrons out of them.

“The solvent takes electrons away, and the system tries to balance by moving electrons,” Michael Strano says. “There’s no sophisticated battery chemistry inside. It’s just a particle and you put it into solvent and it starts generating an electric field.”

“This research shows how to extract the electric energy stored in an electronic material for on-site electrochemical synthesis,” says Jun Yao, an assistant professor of electrical and computer engineering at the University of Massachusetts at Amherst. “The beauty is that it points to a generic methodology that can be readily expanded to the use of different materials and applications in different synthetic systems.”

This version of the particles can generatee 0.7 volts of electricity per particle. In this study, the researchers showed that they can make arrays of hundreds of particles in a small test tube. This “packed bed” reactor generates enough energy to power a chemical reaction called alcohol oxidation. Usually, this reaction is not carried out by using electrochemistry because it needs too much external current.

In his work in the future, Strano wants to use this kind of energy generation to build polymers using only carbon dioxide as a starting material. In a project relevant to this one, he has already created polymers that can regenerate themselves using carbon dioxide as a material that is powered by solar energy. His work was an inspiration for carbon fixation, the set of chemical reactions that plants use to build sugars from carbon dioxide, using energy from the sun.

In long term, this approach can also be used to power micro- or nanoscale robots. Strano’s lab has started building robots at that scale, which could one day be used as diagnostic or environmental sensors. The notion of being able to collect energy from the environment to power these kinds of robots is appealing, Strano says.

“It means you don’t have to put the energy storage onboard,” he says. “What we like about this mechanism is that you can take the energy, at least in part, from the environment.”

This research was funded by the U.S. Department of Energy, and a seed grant from the MIT Energy Initiative.