Chao Wang (right), a Johns Hopkins assistant professor of chemical and biomolecular engineering, in his lab with postdoctoral fellow Lei Wang (left), another author of the Science paper. Image: Will Kirk/Johns Hopkins University.A new method for increasing the reactivity of ultrathin nanosheets, just a few atoms thick, could someday make fuel cells for hydrogen cars cheaper, finds a new study by a team of US researchers. A report of their findings, published in a paper in Science, offers the promise of faster, cheaper production of electrical power using fuel cells, as well as of bulk chemicals and materials such as hydrogen.
"Every material experiences surface strain due to the breakdown of the material's crystal symmetry at the atomic level. We discovered a way to make these crystals ultrathin, thereby decreasing the distance between atoms and increasing the material's reactivity," says Chao Wang, an assistant professor of chemical and biomolecular engineering at Johns Hopkins University, and one of the study's corresponding authors.
Strain is, in short, the deformation of any material. For example, when a piece of paper is bent, it is effectively disrupted at the smallest, atomic level; the intricate lattices that hold the paper together are forever changed.
In this study, Wang and colleagues manipulated the strain effect, or distance between atoms, causing the material to change dramatically. By making those lattices incredibly thin, roughly a million times thinner than a strand of human hair, the material becomes much easier to manipulate, analogous to the way one piece of paper is easier to bend than a thicker stack of paper.
"We're essentially using force to tune the properties of thin metal sheets that make up electrocatalysts, which are part of the electrodes of fuel cells," explains Jeffrey Greeley, professor of chemical engineering at Purdue University and another one of the paper's corresponding authors. "The ultimate goal is to test this method on a variety of metals."
"By tuning the materials' thinness, we were able to create more strain, which changes the material's properties, including how molecules are held together. This means you have more freedom to accelerate the reaction you want on the material's surface," explains Wang.
One example of how optimizing reactions can be useful is in increasing the activity of the catalysts used for fuel cell cars. While fuel cells represent a promising technology for powering emission-free electrical vehicles, they currently require expensive precious metal catalysts such as platinum and palladium, limiting their practical viability to the vast majority of consumers. A more active catalyst for fuel cells could get away with using less platinum or palladium and clear the way for widespread adoption of green, renewable energy.
Wang and his colleagues estimate that their new method can increase catalyst activity by 10 to 20 times, allowing a 90% reduction in the use of precious metals compared with what is currently required to power a fuel cell.
"We hope that our findings can someday aid in the production of cheaper, more efficient fuel cells to make environmentally-friendly cars more accessible for everybody," says Wang.
This story is adapted from material from Johns Hopkins University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.