Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stanford scientists use nanotechnology to boost the performance of key industrial catalyst

18.05.2017

A tiny amount of squeezing or stretching can produce a big boost in catalytic performance, according to a new study led by scientists at Stanford University and SLAC National Accelerator Laboratory.

The discovery, published May 18 in Nature Communications, focuses on an industrial catalyst known as cerium oxide, or ceria, a spongy material commonly used in catalytic converters, self-cleaning ovens and various green-energy applications, such as fuel cells and solar water splitters.


This colorized transmission electron microscopy of ceria ultrathin film reveals that individual atoms (shown as dots) shift under intense pressure.

Credit: Sang?Chul?Lee

"Ceria stores and releases oxygen as needed, like a sponge," said study co-author Will Chueh, an assistant professor of materials science and engineering at Stanford and a faculty scientist at SLAC.

"We discovered that stretching and compressing ceria by a few percent dramatically increases its oxygen storage capacity. This finding overturns conventional wisdom about oxide materials and could lead to better catalysts."

Catalytic converters

Ceria has long been used in catalytic converters to help remove air pollutants from vehicle exhaust systems.

"In your car, ceria grabs oxygen from poisonous nitrogen oxide, creating harmless nitrogen gas," said study lead author Chirranjeevi Balaji Gopal, a former postdoctoral researcher at Stanford. "Ceria then releases the stored oxygen and uses it to convert lethal carbon monoxide into benign carbon dioxide."

Studies have shown that squeezing and stretching ceria causes nanoscale changes that affect its ability to store oxygen.

"The oxygen storage capacity of ceria is critical to its effectiveness as a catalyst," said study co-author Aleksandra Vojvodic, a former staff scientist at SLAC now at the University of Pennsylvania, who led the computational aspect of this work. "The theoretical expectation based on previous studies is that stretching ceria would increase its capacity to store oxygen, while compressing would lower its storage capacity."

To test this prediction, the research team grew ultrathin films of ceria, each just a few nanometers thick, on top of substrates made of different materials. This process subjected the ceria to stress equal to 10,000 times the Earth's atmosphere. This enormous stress caused the molecules of ceria to separate and squeeze together a distance of less than one nanometer.

Surprise results

Typically, materials like ceria relieve stress by forming defects in the film. But atomic-scale analysis revealed a surprise.

"Using high-resolution transmission electron microscopy to resolve the position of individual atoms, we showed that the films remain stretched or compressed without forming such defects, allowing the stress to remain in full force," said Robert Sinclair, a professor of materials science and engineering at Stanford.

To measure the impact of stress under real-world operating conditions, the researchers analyzed the ceria samples using the brilliant beams of X-ray light produced at Lawrence Berkeley National Laboratory's Advanced Light Source.

The results were even more surprising.

"We discovered that the strained films exhibited a fourfold increase in the oxygen storage capacity of ceria," Gopal said. "It doesn't matter if you stretch it or compress it. You get a remarkably similar increase."

The high-stress technique used by the research team is readily achievable through nanoengineering, Chueh added.

"This discovery has significant implications on how to nanoengineer oxide materials to improve catalytic efficiency for energy conversion and storage," he said. "It's important for developing solid oxide fuel cells and other green-energy technologies, including new ways to make clean fuels from carbon dioxide or water."

###

Other Stanford co-authors of the study are Max Garcia-Melchor, now at Trinity College Dublin (Ireland), and graduate students Sang Chul Lee, Zixuan Guan, Yezhou Shi and Matteo Monti. Additional co-authors are Andrey Shavorskiy of Lund University (Sweden) and Hendrik Bluhm of Lawrence Berkeley National Laboratory.

Media Contact

Mark Shwartz
mshwartz@stanford.edu
650-723-9296

 @stanford

http://news.stanford.edu/ 

Mark Shwartz | EurekAlert!

More articles from Materials Sciences:

nachricht Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University

nachricht 3D-Printing: Support structures to prevent vibrations in post-processing of thin-walled parts
12.07.2018 | Fraunhofer-Institut für Produktionstechnologie IPT

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Research finds new molecular structures in boron-based nanoclusters

13.07.2018 | Materials Sciences

Algae Have Land Genes

13.07.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>