Engineering news
The technique, which uses tiny carbon particles submerged in a solvent to generate current, could be used to drive chemical reactions or to power micro- or nanoscale robots.
“This mechanism is new, and this way of generating energy is completely new,” said chemical engineer Professor Michael Strano. “This technology is intriguing because all you have to do is flow a solvent through a bed of these particles.”
The researchers showed that they could use the electric current to drive alcohol oxidation, an organic chemical reaction that is important in the chemical industry.
In 2010, Strano demonstrated for the first time that carbon nanotubes can generate ‘thermopower waves’. When a carbon nanotube is coated with a layer of fuel, moving pulses of heat – thermopower waves – travel along the tube, creating an electrical current.
That work led senior author Strano and his students to uncover a related feature of carbon nanotubes. They found that when part of a nanotube is coated with a Teflon-like polymer, it creates an asymmetry that makes it possible for electrons to flow from the coated to the uncoated part of the tube, generating an electrical current. Those electrons can be drawn out by submerging the particles in a solvent that is ‘hungry’ for electrons.
To harness this capability, the team created electricity-generating particles by grinding up carbon nanotubes and forming them into a sheet of paper-like material. One side was coated with a Teflon-like polymer, and the researchers then cut out small particles that were 250 microns by 250 microns.
When these particles were submerged in an organic solvent such as acetonitrile, the solvent adhered to the uncoated surface of the particles and began pulling electrons out of them.
The current version of the material can generate about 0.7 volts of electricity per particle. The researchers also showed that they can form arrays of hundreds of particles in a small test tube. This ‘packed bed’ reactor generates enough energy to power alcohol oxidation, in which an alcohol is converted to an aldehyde or a ketone. This reaction is not normally done using electrochemistry because it would require too much external current.
“Because the packed bed reactor is compact, it has more flexibility in terms of applications than a large electrochemical reactor," said graduate student Ge Zhang. “The particles can be made very small, and they don't require any external wires in order to drive the electrochemical reaction.”
In future work, Strano hopes to use the method to build polymers using only carbon dioxide as a starting material. In a related project, he has already created polymers that can regenerate themselves using carbon dioxide as a building material, in a process powered by solar energy. That work was inspired by carbon fixation, the set of chemical reactions that plants use to build sugars from carbon dioxide using energy from the sun.
In the longer term, the new energy generation technique could also be used to power micro- or nanoscale robots. Strano's lab has already begun building robots at that scale, which could one day be used as diagnostic or environmental sensors.
The idea of being able to ‘scavenge’ energy from the environment to power robots is appealing, Strano said. “It means you don't have to put the energy storage on board… What we like about this mechanism is that you can take the energy, at least in part, from the environment.”
The research was published in Nature Communications. The lead authors were Albert Tianxiang Liu and Yuichiro Kunai. Other authors included Anton Cottrill, Amir Kaplan, Hyunah Kim, Ge Zhang, Rafid Mollah and Yannick Eatmon.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.