Platinum nanoparticles may radically improve fuel cells

This nanotech-based catalyst would put electric cars — among other ideas and products — on a much faster track.

From the link:

In the quest for efficient, cost-effective and commercially viable fuel cells, scientists at Cornell University’s Energy Materials Center have discovered a catalyst and catalyst-support combination that could make fuel cells more stable, conk-out free, inexpensive and more resistant to carbon monoxide poisoning.

The research, “Highly Stable and CO-Tolerant Pt/Ti_0.7W_0.3O₂ Electrocatalyst for Proton-Exchange Membrane Fuel Cells,” (Journal of the American Chemical Society, July 12, 2010) led by Hector D. Abruna, Cornell professor of Chemistry and Chemical Biology and director of the Energy Materials Center at Cornell (emc2); Francis J. DiSalvo, Cornell professor Chemistry and Chemical Biology; Deli Wang, post doctoral researcher; Chinmayee V. Subban, graduate student; Hongsen Wang, research associate; and Eric Rus, graduate student.

Hydrogen fuel cells offer an appealing alternative to gasoline-burning cars: They have the potential to power vehicles for long distances using hydrogen as fuel, mitigate carbon dioxide production and emit only water vapor.

However, fuel cells generally require very pure hydrogen to work. That means that conventional fuels must be stripped of carbon monoxide – a process that is too expensive to make fuel cells commercially viable.

Fuel cells work by electrochemically decomposing fuel instead of burning it, converting energy directly into electricity

Lithium-air battery news

Good news, that is. A nanotech catalyst improves the efficiency of lithium-air batteries to record levels and gets them that much closer to practical application in places like electric vehicles.

From the link:

A catalyst developed by researchers at MIT makes rechargeable lithium-air batteries significantly more efficient–a step toward making these high-energy-density batteries practical for use in electric vehicles and elsewhere.

The catalyst consists of nanoparticles of a gold and platinum alloy; in testing it was able to return 77 percent of the energy used to charge the battery as electricity when discharged. That’s up from the previously published record of about 70 percent, the researchers say. The work, which was reported online this week in the Journal of the American Chemical Society, suggests a new approach to lithium-air battery catalysts that could lead to the even higher efficiencies of 85 to 90 percent needed for commercial batteries.

Lithium-air batteries, which generate electricity by reacting lithium metal and oxygen from the air, are attractive for their potential to store vast amounts of energy. They could be a practical way to store more than three times as much energy, by weight, as today’s lithium-ion batteries, extending the range of electric vehicles, for example.

Air catalyst: Gold and platinum alloy nanoparticles (the dark areas) sit on top of a carbon black substrate (the lighter patterns); together, these materials improve the efficiency of lithium-air batteries.
Credit: Yi-Chun Lu

Dyeing graphene

I’ve done plenty of blogging on graphene, the world’s thinnest material at a single atom of carbon, and I’ve even posted an actual image of graphene. Now scientists at Northwestern University have found a way to actually dye the material — well, technically the method is more a reverse dyeing — but the result is a great reduction in cost when imaging graphene for certain applications.

From the link:

The useful tool is the dye fluorescein, and Jiaxing Huang, assistant professor of materials science and engineering at the McCormick School of Engineering and Applied Science, and his research group have used the dye to create a new imaging technique to view graphene, a one-atom thick sheet that scientists believe could be used to produce low-cost carbon-based transparent and flexible electronics.

Their results were recently published in the Journal of the American Chemical Society.

Being the world’s thinnest materials, graphene and its derivatives such as graphene oxide are quite challenging to see. Current imaging methods for graphene materials typically involve expensive and time-consuming techniques. For example, atomic force microscopy (AFM), which scans materials with a tiny tip, is frequently used to obtain images of graphene materials. But it is a slow process that can only look at small areas on smooth surfaces. Scanning electron microscopy (SEM), which scans a surface with high-energy electrons, only works if the material is placed in vacuum. Some optical microscopy methods are available, but they require the use of special substrates, too.

Update: Here’s a press release on this exact topic. Find the full text of the release (plus images) below the fold.

Highest surface area ever

For a porous material, this particular is a nanoporous product.

The release:

New nanoporous material has highest surface area yet

ANN ARBOR, Mich.—University of Michigan researchers have developed a nanoporous material with a surface area significantly higher than that of any other porous material reported to date.

The work, by a team led by associate professor of chemistry Adam Matzger, is described in a paper published online March 6 in the Journal of the American Chemical Society.

“Surface area is an important, intrinsic property that can affect the behavior of materials in processes ranging from the activity of catalysts to water detoxification to purification of hydrocarbons,” Matzger said.

Until a few years ago, the upper limit for surface area of porous materials was thought to be around 3,000 square meters per gram. Then in 2004, a U-M team that included Matzger reported development of a material known as MOF-177 that set a new record. MOF-177 belonged to a new class of materials known as metal-organic frameworks—scaffold-like structures made up of metal hubs linked together with struts composed of organic compounds. Just one gram of MOF-177 has the surface area of a football field.

“Pushing beyond that point has been difficult,” Matzger said, but his group achieved the feat with the new material, UMCM-2 (University of Michigan Crystalline Material-2), which has a record-breaking surface area of more than 5,000 square meters per gram.

The researchers used a technique called coordination copolymerization to produce the new material. Previously, they used the same method to create a similar material, UMCM-1, which was made up of six, microporous cage-like structures surrounding a large, hexagonal channel. By using a slightly different combination of ingredients, Matzger’s group came up with UMCM-2, which is composed of fused cages of various sizes and does not have the channel found in UMCM-1.

“The new structure is a bit surprising and shows how the coordination copolymerization method has real potential for new materials discovery,” Matzger said.

In the quest for new materials capable of compactly storing large amounts of hydrogen, researchers have assumed that increasing the surface area of porous materials will result in greater storage capacity. Interestingly, the hydrogen-holding ability of UMCM-2, while high, is no greater than that of existing materials in the same family, suggesting that surface area alone is not the key to hydrogen uptake. Even so, UMCM-2 is useful for helping define future research directions, Matzger said. “I think we needed this compound to demonstrate that high surface area alone is not enough for hydrogen storage.”

 

###

 

Matzger’s coauthors on the paper are postdoctoral researcher Kyoungmoo Koh and research scientist Antek Wong-Foy. The researchers received funding from the U.S. Department of Energy.

For more information: Adam Matzger: http://www.ns.umich.edu/htdocs/public/experts/ExpDisplay.php?ExpID=1264

Journal of the American Chemical Society: http://pubs.acs.org/doi/abs/10.1021/ja809985t

High efficiency polymer solar cells

The release:

UCLA researchers create polymer solar cells with higher efficiency levels

By

Wileen Wong Kromhout

| 11/26/2008

Currently, solar cells are difficult to handle, expensive to purchase and complicated to install. The hope is that consumers will one day be able to buy solar cells from their local hardware store and simply hang them like posters on a wall.

 

A new study by researchers at the UCLA Henry Samueli School of Engineering and Applied Science has shown that the dream is one step closer to reality. Reporting in the Nov. 26 edition of the Journal of the American Chemical Society, Yang Yang, a professor of materials science and engineering, and colleagues describe the design and synthesis of a new polymer, or plastic, for use in solar cells that has significantly greater sunlight absorption and conversion capabilities than previous polymers.

 

The research team found that substituting a silicon atom for carbon atom in the backbone of the polymer markedly improved the material’s photovoltaic properties. This silole-containing polymer can also be crystalline, giving it great potential as an ingredient for high-efficiency solar cells.

 

“With the reality of today’s energy crisis, a new-game changing technology is required to make solar cells more popular,” Yang said. “We hope that our newly synthesized polymer can eventually be used on solar cells far beyond their current rooftop applications. Imagine a house or car covered and powered by flexible solar films. Our dream is to see solar cells used everywhere.”

 

Polymers are lightweight, low-cost plastics used in packaging materials and inexpensive products like insulators, pipes, household products and toys. Polymer solar cells utilize organic compounds to produce electricity from sunlight. They are much cheaper to produce than traditional silicon-based solar cells and are also environmentally friendly.

 

But while polymer solar cells have been around for several years, their efficiency has, until recently, been low. The new polymer created by Yang’s team reached 5.1 percent efficiency in the published study but has in a few months improved to 5.6 percent in the lab. Yang and his team have proven that the photovoltaic material they use on their solar cells is one of the most efficient based on a single-layer, low-band-gap polymer.

 

At a lower band gap, the polymer solar cell can better utilize the solar spectrum, thereby absorbing more sunlight. At a higher band gap, light is not easily absorbed and can be wasted.

 

“Previously, the synthesizing process for the polymer was very complicated. We’ve been able to simplify the process and make it much easier to mass produce,” said Jianhui Hou, UCLA postdoctoral researcher and co-author of the study. “Though this is a milestone achievement, we will continue to work on improving the materials. Ideally we’d like to push the performance of the solar cell to higher than 10 percent efficiency. We know the potential is there.”

 

“We hope that solar cells will one day be as thin as paper and can be attached to the surface of your choice,” added co-author Hsiang-Yu Chen, a UCLA graduate student in engineering. “We’ll also be able to create different colors to match different applications.”

 

The study was funded by Solarmer Energy Inc. and a UC Discovery Grant. Solarmer Energy Inc. has recently licensed the technology from UCLA for commercialization.

 

The UCLA Henry Samueli School of Engineering and Applied Science, established in 1945, offers 28 academic and professional degree programs, including an interdepartmental graduate degree program in biomedical engineering. Ranked among the top 10 engineering schools at public universities nationwide, the school is home to six multimillion-dollar interdisciplinary research center in space exploration, wireless sensor systems, nanotechnology, nanomanufacturing and nanoelectronics, all funded by federal and private agencies. For more information, visit www.engineer.ucla.edu.