Researchers at the National Institute of Standards and Technology (NIST) have developed a fast, simple process for making platinum 'nano-raspberries' -- microscopic clusters of nanoscale particles of the precious metal.
The berry-like shape is significant because it has a high surface area, which is helpful in the design of catalysts. Even better news for industrial chemists: the researchers figured out when and why the berry clusters clump into larger bunches of 'nano-grapes.'
Colorized micrographs of platinum nanoparticles made at NIST. The raspberry color suggests the particles' corrugated shape, which offers high surface area for catalyzing reactions in fuel cells. Individual particles are 3 to 4 nanometers (nm) in diameter but can clump into bunches of 100 nm or more under specific conditions discovered in a NIST study.
Courtesy of Curtin/NIST
The research could help make fuel cells more practical. Nanoparticles can act as catalysts to help convert methanol to electricity in fuel cells. NIST's 40-minute process for making nano-raspberries, described in a new paper,* has several advantages. The high surface area of the berries encourages efficient reactions. In addition, the NIST process uses water, a benign or 'green' solvent. And the bunches catalyze methanol reactions consistently and are stable at room temperature for at least eight weeks.
Although the berries were made of platinum, the metal is expensive and was used only as a model. The study will actually help guide the search for alternative catalyst materials, and clumping behavior in solvents is a key issue.
For fuel cells, nanoparticles often are mixed with solvents to bind them to an electrode. To learn how such formulas affect particle properties, the NIST team measured particle clumping in four different solvents for the first time. For applications such as liquid methanol fuel cells, catalyst particles should remain separated and dispersed in the liquid, not clumped.
'Our innovation has little to do with the platinum and everything to do with how new materials are tested in the laboratory,' project leader Kavita Jeerage says. 'Our critical contribution is that after you make a new material you need to make choices. Our paper is about one choice: what solvent to use. We made the particles in water and tested whether you could put them in other solvents. We found out that this choice is a big deal.'
The NIST team measured conditions under which platinum particles, ranging in size from 3 to 4 nanometers (nm) in diameter, agglomerated into bunches 100 nm wide or larger. They found that clumping depends on the electrical properties of the solvent. The raspberries form bigger bunches of grapes in solvents that are less 'polar,' that is, where solvent molecules lack regions with strongly positive or negative charges, (water is a strongly polar molecule).
The researchers expected that. What they didn't expect is that the trend doesn't scale in a predictable way. The four solvents studied were water, methanol, ethanol and isopropanol, ordered by decreasing polarity. There wasn't much agglomeration in methanol; bunches got about 30 percent bigger than they were in water. But in ethanol and isopropanol, the clumps got 400 percent and 600 percent bigger, respectively -- really humongous bunches. This is a very poor suspension quality for catalytic purposes.
Because the nanoparticles clumped up slowly and not too much in methanol, the researchers concluded that the particles could be transferred to that solvent, assuming they were to be used within a few days -- effectively putting an expiration date on the catalyst.
Two college students in NIST's Summer Undergraduate Research Fellowship (SURF) program helped with the extensive data collection required for the study.
*I. Sriram, A.E. Curtin, A.N. Chiaramonti, J.H. Cuchiaro, A.D. Weidner, T.M. Tingley, L.F. Greenlee and K.M. Jeerage. Stability and phase transfer of catalytically active platinum nanoparticle suspensions. Journal of Nanoparticle Research 17:230.DOI 10.1007/s11051-015-3034-1. Published online May 22.
Laura Ost | EurekAlert!
New design improves performance of flexible wearable electronics
23.06.2017 | North Carolina State University
Plant inspiration could lead to flexible electronics
22.06.2017 | American Chemical Society
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
28.06.2017 | Physics and Astronomy
28.06.2017 | Physics and Astronomy
28.06.2017 | Health and Medicine