University of Wisconsin: Simulating complex catalysts key to making cheap, powerful fuel cells


Cheap Fuel Cells 081016 id44194Using a unique combination of advanced computational methods, University of Wisconsin-Madison chemical engineers have demystified some of the complex catalytic chemistry in fuel cells — an advance that brings cost-effective fuel cells closer to reality.

“Understanding reaction mechanisms is the first step toward eventually replacing expensive platinum in fuel cells with a cheaper material,” says Manos Mavrikakis, a UW-Madison professor of chemical and biological engineering.
Mavrikakis and colleagues at Osaka University in Japan published details of the advance Monday, Aug. 8, in the journal Proceedings of the National Academy of Sciences (“Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces”).

 

Methanol Molecules
Modeling how methanol interacts with platinum catalysts inside fuel cells in realistic environments becomes even more complicated because distances between the atoms can change as molecules dance near the charged surface. (Image: Manos Mavrikakis)
 

Fuel cells generate electricity by combining electrons and protons — provided by a chemical fuel such as methanol — with oxygen from the air. To make the reaction that generates protons faster, fuel cells typically contain catalysts. With the right catalyst and enough fuel and air, fuel cells could provide power very efficiently.

 

Someday, fuel cells could make laptop batteries obsolete. Mere tablespoons of methanol could potentially provide up to 20 hours of continuous power. But alternatives to the expensive platinum catalyst in today’s fuel cells haven’t emerged because scientists still don’t fully understand the complicated chemistry required to produce protons and electrons from fuels.

 

And finding a good catalyst is no trivial task.

 

“People arrived at using platinum for a catalyst largely by trial and error, without understanding how the reaction takes place,” says Mavrikakis. “Our efforts developed a big picture of how the reaction is happening, and we hope to do the same analysis with other materials to help find a cheaper alternative.”

 

At first glance, the chemistry sounds straightforward: Methanol molecules awash in a watery milieu settle down on a platinum surface and give up one of their four hydrogen atoms. The movement of those electrons from that hydrogen atom make an electric current.

 

In reality, the situation is not so simple.

 

“All of these molecules, the water and the methanol, are actually dancing around the surface of the catalyst and fluctuating continuously,” says Mavrikakis. “Following the dynamics of these fluctuating motions all the time, and in the presence of an externally applied electric potential, is really very complicated.”

 

The water molecules are not wallflowers, sitting on the sidelines of the methanol molecules reacting with platinum; rather, they occasionally cut in to the chemical dance. And varying voltage on the electrified surface of the platinum catalyst tangles the reaction’s tempo even further.

 

Previously, chemists only simulated simplified scenarios — fuel cells without any water in the mix, or catalytic surfaces that didn’t crackle with electricity. Unsurprisingly, conclusions based on such oversimplifications failed to fully capture the enormous complexity of real-world reactions.

 

Mavrikakis and colleagues combined their expertise in two powerful computational techniques to create a more accurate description of a very complex real environment.
They first used density functional theory to solve for quantum mechanical forces and energies between individual atoms, then built a scheme upon those results using molecular dynamics methods to simulate large ensembles of water and methanol molecules interacting among themselves and with the platinum surface.
The detailed simulations revealed that the presence of water in a fuel cell plays a huge role in dictating which hydrogen atom breaks free from methanol first — a result that simpler methods could never have captured. Electric charge also determined the order in which methanol breaks down, surprisingly switching the preferred first step at the positive electrode.

 

This type of information enables scientists to predict which byproducts might accumulate in a reaction mixture, and select better ingredients for future fuel cells.
“Modeling enables you to come up with an informed materials design,” says Mavrikakis, whose work was supported by the Department of Energy and the National Science Foundation. “We plan to investigate alternative fuels, and a range of promising and cheaper catalytic materials.”

 

The results represent the culmination of six years of effort across two continents. Jeffrey Herron, the first author on the paper, started developing the methodologies during a summer visit to work under the paper’s second author, Professor Yoshitada Morikawa in the Division of Precision Science & Technology and Applied Physics at Osaka University.
Herron, who completed his doctorate in 2015 and is now a senior engineer for The Dow Chemical Company, further refined these approaches under Mavrikakis’ guidance over several subsequent years in Madison.
“A lot of work over many years went into this paper,” says Mavrikakis. “The world needs fuel cells, but without understanding how the reaction takes place, there is no rational way to improve.”
Source: University of Wisconsin-Madison

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SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA

Chairman Terry: “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development.”

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on:

“Nanotechnology: Understanding How Small Solutions Drive Big Innovation.”

 

 

electron-tomography

“Great Things from Small Things!” … We Couldn’t Agree More!

 

Subcommittee Examines Breakthrough Nanotechnology Opportunities for America


Applications-of-Nanomaterials-Chart-Picture1SUBCOMMITTE EXAMINES BREAKTHROUGH NANOTECHNOLOGY OPPORTUNITIES FOR AMERICA
July 29, 2014

WASHINGTON, DCThe Subcommittee on Commerce, Manufacturing, and Trade, chaired by Rep. Lee Terry (R-NE), today held a hearing on “Nanotechnology: Understanding How Small Solutions Drive Big Innovation.” Nanotechnology is science, engineering, and technology conducted at the nanoscale, which is approximately 1 to 100 nanometers (one nanometer is a billionth of a meter). This technology brings great opportunities to advance a broad range of industries, bolster our U.S. economy, and create new manufacturing jobs. Members heard from several nanotech industry leaders about the current state of nanotechnology and the direction that it is headed.UNIVERSITY OF WATERLOO - New $5 million lab

“Just as electricity, telecommunications, and the combustion engine fundamentally altered American economics in the ‘second industrial revolution,’ nanotechnology is poised to drive the next surge of economic growth across all sectors,” said Chairman Terry.

 

 

Applications of Nanomaterials Chart Picture1

Dr. Christian Binek, Associate Professor at the University of Nebraska-Lincoln, explained the potential of nanotechnology to transform a range of industries, stating, “Virtually all of the national and global challenges can at least in part be addressed by advances in nanotechnology. Although the boundary between science and fiction is blurry, it appears reasonable to predict that the transformative power of nanotechnology can rival the industrial revolution. Nanotechnology is expected to make major contributions in fields such as; information technology, medical applications, energy, water supply with strong correlation to the energy problem, smart materials, and manufacturing. It is perhaps one of the major transformative powers of nanotechnology that many of these traditionally separated fields will merge.”

Dr. James M. Tour at the Smalley Institute for Nanoscale Science and Technology at Rice University encouraged steps to help the U.S better compete with markets abroad. “The situation has become untenable. Not only are our best and brightest international students returning to their home countries upon graduation, taking our advanced technology expertise with them, but our top professors also are moving abroad in order to keep their programs funded,” said Tour. “This is an issue for Congress to explore further, working with industry, tax experts, and universities to design an effective incentive structure that will increase industry support for research and development – especially as it relates to nanotechnology. This is a win-win for all parties.”

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Professor Milan Mrksich of Northwestern University discussed the economic opportunities of nanotechnology, and obstacles to realizing these benefits. He explained, “Nanotechnology is a broad-based field that, unlike traditional disciplines, engages the entire scientific and engineering enterprise and that promises new technologies across these fields. … Current challenges to realizing the broader economic promise of the nanotechnology industry include the development of strategies to ensure the continued investment in fundamental research, to increase the fraction of these discoveries that are translated to technology companies, to have effective regulations on nanomaterials, to efficiently process and protect intellectual property to ensure that within the global landscape, the United States remains the leader in realizing the economic benefits of the nanotechnology industry.”

James Phillips, Chairman & CEO at NanoMech, Inc., added, “It’s time for America to lead. … We must capitalize immediately on our great University system, our National Labs, and tremendous agencies like the National Science Foundation, to be sure this unique and best in class innovation ecosystem, is organized in a way that promotes nanotechnology, tech transfer and commercialization in dramatic and laser focused ways so that we capture the best ideas into patents quickly, that are easily transferred into our capitalistic economy so that our nation’s best ideas and inventions are never left stranded, but instead accelerated to market at the speed of innovation so that we build good jobs and improve the quality of life and security for our citizens faster and better than any other country on our planet.”

Chairman Terry concluded, “Nanotech is a true science race between the nations, and we should be encouraging the transition from research breakthroughs to commercial development. I believe the U.S. should excel in this area.”

– See more at: http://energycommerce.house.gov/press-release/subcommittee-examines-breakthrough-nanotechnology-opportunities-america#sthash.YnSzFU10.dpuf

Molecular Dynanmics: Visualizing the Invisible


Palladium Nano id36700

Panagiotis Grammatikopoulos in the OIST Nanoparticles by Design Unit simulates the interactions of particles that are too small to see, and too complicated to visualize. In order to study the particles’ behavior, he uses a technique called molecular dynamics.

This means that every trillionth of a second, he calculates the location of each individual atom in the particle based on where it is and which forces apply. He uses a computer program to make the calculations, and then animates the motion of the atoms using visualization software. The resulting animation illuminates what happens, atom-by-atom, when two nanoparticles collide. Grammatikopoulos calls this a virtual experiment.

He knows what the atoms in his starting nanoparticles look like. He knows their motion follows the laws of Newtonian physics. His colleagues have seen what the resulting particles look like after collision experiments. Once his simulation is complete, Grammatikopoulos compares his end products with his colleagues to check his accuracy. Grammatikopoulos most recently simulated how palladium nanoparticles interact, published in Scientific Reports on July 22, 2014 (“Coalescence-induced crystallisation wave in Pd nanoparticles”).

 

simulation of palladium nanoparticles colliding at different temperatures

Grammatikopoulos simulated two palladium nanoparticles colliding at different temperatures. The hotter the temperature, the more homogenous the resulting product, and the further the atoms in the particle crystallize. (click on image to enlarge)

Palladium is an expensive but highly efficient catalyst that lowers the energy required to start many chemical reactions. Researchers can make palladium even more efficient by designing palladium nanoparticles, which use the same mass of palladium in tinier pieces, increasing surface area. The more surface area a catalyst has, the more effective it is, because there are more active sites where elements can meet and reactions can occur.

However, shrinking a material to only a few nanometers can change some of the properties of that material. For example, all nanoparticles melt at cooler temperatures than they would normally, which changes what happens when two particles collide. Ordinarily, two particles will collide and release a small amount of heat, but the particles remain more or less the same. But when two nanoparticles collide, sometimes the heat released melts the surface of the two particles, and they fuse together.

Palladium Crystallization at 300K. Grammatikopoulos created this simulation of palladium nanoparticles colliding at 300 Kevin, or about 27 degrees Celsius. The nanoparticles meet, then fuse, then crystallize in orderly planes.

Grammatikopoulos simulated palladium nanoparticles colliding and fusing at different temperatures. He determined that each time the particles fused, their atoms would start to crystallize into orderly rows and planes. At higher temperatures, the particles fuse into one homogeneous structure. At lower temperatures, the products look like classic snowmen, with a few parts that had crystallized with different orientations.

“The simulation gives you an understanding of physical processes,” said Grammatikopoulos. Before his research, Grammatikopoulos could not explain why all the palladium nanoparticles his lab created had a crystalline structure. Furthermore, he noticed that many palladium nanoparticles grew protrusions, giving the particles a lumpy shape. “Since the protrusions stick out, they bond more easily with other molecules,” Grammatikopoulos explained. “I’m not sure yet if it’s beneficial, but it’s definitely affecting the catalytic properties.”

Palladium Crystallization at 1000K. Grammatikopoulos created this simulation of palladium nanoparticles colliding at 1000 Kevin, or about 727 degrees Celsius. At this hot temperature, the nanoparticles meet, fuse, and crystallize, forming one large homogenous product.

This study establishes some ground rules and explains certain properties of palladium nanoparticles. Understanding these properties could help design other nanoparticles out of other materials that would rival palladium’s abilities as a catalyst. Palladium plays a role in thousands of important reactions, from making drugs to creating new biofuels. For example, Prof. Mukhles Sowwan’s Nanoparticles by Design Unit and Prof. Igor Goryanin’s Biological Systems Unit at OIST are working with palladium-catalyzed reactions to improve the efficiency of microbial fuel cells. Better palladium nanoparticles will propel this research forward.
“We need to understand the basic science,” explained Sowwan, who is Grammatikopoulos’ advisor. Sowwan says that the field of nanoscience is only starting to move towards applying the research, because there is still so much to learn about the properties of nanoparticles. “If you build something without understanding the basics,” Sowwan said, “you will not be able to explain the results.”
Source: By Poncie Rutsch, Okinawa Institute of Science and Technology