A scanning electron microscope image of the nanostructured iridium oxide, colored to represent the catalytic combustion. Image: Army Research Lab.
A scanning electron microscope image of the nanostructured iridium oxide, colored to represent the catalytic combustion. Image: Army Research Lab.

In a paper in Cell Reports Physical Science, researchers from the University of Connecticut (UConn) and the US Army Research Laboratory (ARL) report their development of a novel portable pyroelectric technology.

Pyroelectric energy research focuses on generating energy from heat that would otherwise be wasted in a catalytic chemical reaction. When pyroelectric materials are heated, their polarization changes, leading to an electron flow that generates electricity. These materials are commonly used in household devices like motion sensor lights, which detect body heat to determine when someone is near.

Anytime there is a catalytic reaction, heat is generated. Pyroelectric devices could harness that heat and use it as energy. For example, a combustion engine in a car produces heat that, with this kind of technology, could be used to power the electrical functions of the car that otherwise rely on battery power. The ARL is particularly interested in this technology because it could provide more power with less weight, which is important for soldiers carrying heavy bags.

While scientists have been experimenting with pyroelectric power for decades, the technology proposed in the new paper is completely novel. "Something like that doesn't exist," says Pamir Alpay, associate dean for research and industrial partnerships at UConn. "It would give you the opportunity to recover some things that just go to waste."

The novel pyroelectric technology is portable and has an extended lifetime. It uses on-chip catalytic combustion of methanol, a high-energy fuel, to generate heat, by combusting methanol vapor over a 440nm-thick film of nanostructured iridium oxide on platinized silicon wafers. The pyroelectric material, which in this case is lanthanum-doped lead zirconate titanate, converts the heat from this reaction to usable power.

Iridium is a dense, corrosion and heat-resistant metal, making it an excellent candidate for this application. The nanostructured iridium oxide first becomes activated at temperatures as low as 105°C and fully catalyzes the combustion of methanol to carbon dioxide at 120°C. This is an advantage compared to platinum-based catalysts, which do not achieve full conversion until 150°C, meaning less heat must be applied to the device for it to be fully effective.

This on-chip combustion technology has a 90% combustion efficiency rate and would be significantly more powerful than the lithium-ion batteries currently used in most electronic devices. This is because the energy density of methanol is 22 times greater than a lithium-ion battery.

While this study only provided researchers with a preliminary version of this technology, it could have far-reaching applications. Pyroelectric power offers a clean alternative to fossil fuels and nuclear energy, and could have broad energy applications on large and small scales.

Brendan Hanrahan, a staff materials engineer at ARL, led this effort on ARL's side, and operated as a critical hinge to bring the ARL and UConn researchers together for this project. Over the past few years, UConn and ARL have fostered a productive partnership that will likely continue for years to come.

"The key to our successful collaboration is that we play off each other's strengths," says Hanrahan. "Without one another, theories would remain theories and we're just shooting in the dark. So that's why it's such a great partnership."

This story is adapted from material from the University of Connecticut, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.