'Unzipped' Carbon Nanotubes Could Help Energize Fuel Cells and Batteries

Multi-walled carbon nanotubes riddled with defects and impurities on the outside could replace some of the expensive platinum catalysts used in fuel cells and metal-air batteries, according to scientists at Stanford University. Their findings are published in the May 27 online edition of the journal Nature Nanotechnology.

"Platinum is very expensive and thus impractical for large-scale commercialization," said Hongjie Dai, a professor of chemistry at Stanford and co-author of the study. "Developing a low-cost alternative has been a major research goal for several decades."

Over the past five years, the price of platinum has ranged from just below $800 to more than $2,200 an ounce. Among the most promising, low-cost alternatives to platinum is the carbon nanotube -- a rolled-up sheet of pure carbon, called graphene, that's one-atom thick and more than 10,000 times narrower a human hair. Carbon nanotubes and graphene are excellent conductors of electricity and relatively inexpensive to produce.

For the study, the Stanford team used multi-walled carbon nanotubes consisting of two or three concentric tubes nested together. The scientists showed that shredding the outer wall, while leaving the inner walls intact, enhances catalytic activity in nanotubes, yet does not interfere with their ability to conduct electricity.

"A typical carbon nanotube has few defects," said Yanguang Li, a postdoctoral fellow at Stanford and lead author of the study. "But defects are actually important to promote the formation of catalytic sites and to render the nanotube very active for catalytic reactions."

Unzipped

For the study, Li and his co-workers treated multi-walled nanotubes in a chemical solution. Microscopic analysis revealed that the treatment caused the outer nanotube to partially unzip and form nanosized graphene pieces that clung to the inner nanotube, which remained mostly intact.

"We found that adding a few iron and nitrogen impurities made the outer wall very active for catalytic reactions," Dai said. "But the inside maintained its integrity, providing a path for electrons to move around. You want the outside to be very active, but you still want to have good electrical conductivity. If you used a single-wall carbon nanotube you wouldn't have this advantage, because the damage on the wall would degrade the electrical property."

In fuel cells and metal-air batteries, platinum catalysts play a crucial role in speeding up the chemical reactions that convert hydrogen and oxygen to water. But the partially unzipped, multi-walled nanotubes might work just as well, Li added. "We found that the catalytic activity of the nanotubes is very close to platinum," he said. "This high activity and the stability of the design make them promising candidates for fuel cells."

The researchers recently sent samples of the experimental nanotube catalysts to fuel cell experts for testing. "Our goal is to produce a fuel cell with very high energy density that can last very long," Li said.

Multi-walled nanotubes could also have applications in metal-air batteries made of lithium or zinc.

"Lithium-air batteries are exciting because of their ultra-high theoretical energy density, which is more than 10 times higher than today's best lithium ion technology," Dai said. "But one of the stumbling blocks to development has been the lack of a high-performance, low-cost catalyst. Carbon nanotubes could be an excellent alternative to the platinum, palladium and other precious-metal catalysts now in use."

Controversial sites

The Stanford study might also have resolved a long-standing scientific controversy about the chemical structure of catalytic active sites where oxygen reactions occur. "One group of scientists believes that iron impurities are bonded to nitrogen at the active site," Li said. "Another group believes that iron contributes virtually nothing, except to promote active sites made entirely of nitrogen."

To address the controversy, the Stanford team enlisted scientists at Oak Ridge National Laboratory to conduct atomic-scale imaging and spectroscopy analysis of the nanotubes. The results showed clear, visual evidence of iron and nitrogen atoms in close proximity.

"For the first time, we were able to image individual atoms on this kind of catalyst," Dai said. "All of the images showed iron and nitrogen close together, suggesting that the two elements are bonded. This kind of imaging is possible, because the graphene pieces are just one-atom thick."

Dai noted that the iron impurities, which enhanced catalytic activity, actually came from metal seeds that were used to make the nanotubes and were not intentionally added by the scientists. The discovery of these accidental yet invaluable bits of iron offered the researchers an important lesson. "We learned that metal impurities in nanotubes must not be ignored," Dai said.

Other co-authors of the study are Hailiang Wang, Liming Xie and Yongye Liang of Stanford; Wu Zhou, Juan-Carlos Idrobo and Stephen J. Pennycook of Vanderbilt University and Oak Ridge National Laboratory; and Fei Wei of Tsinghua University.

Nature's Billion-Year-Old Battery Key to Storing Energy

New research at Concordia University is bringing us one step closer to clean energy. It is possible to extend the length of time a battery-like enzyme can store energy from seconds to hours, a study published in the Journal of The American Chemical Society shows.

Your Ad Here

Concordia Associate Professor László Kálmán -- along with his colleagues in the Department of Physics, graduate students Sasmit Deshmukh and Kai Tang -- has been working with an enzyme found in bacteria that is crucial for capturing solar energy. Light induces a charge separation in the enzyme, causing one end to become negatively charged and the other positively charged, much like in a battery. In nature, the energy created is used immediately, but Kálmán says that to store that electrical potential, he and his colleagues had to find a way to keep the enzyme in a charge-separated state for a longer period of time. "We had to create a situation where the charges don't want to or are not allowed to go back, and that's what we did in this study," says Kálmán. Kálmán and his colleagues showed that by adding different molecules, they were able to alter the shape of the enzyme and, thus, extend the lifespan of its electrical potential. In its natural configuration, the enzyme is perfectly embedded in the cell's outer layer, known as the lipid membrane. The enzyme's structure allows it to quickly recombine the charges and recover from a charge-separated state. However, when different lipid molecules make up the membrane, as in Kálmán's experiments, there is a mismatch between the shape of the membrane and the enzyme embedded within it. Both the enzyme and the membrane end up changing their shapes to find a good fit. The changes make it more difficult for the enzyme to recombine the charges, thereby allowing the electrical potential to last much longer. "What we're doing is similar to placing a racecar in on snow-covered streets," says Kálmán. The surrounding conditions prevent the racecar from performing as it would on a racetrack, just like the different lipids prevent the enzyme from recombining the charges as efficiently as it does under normal circumstances. Photosynthesis, which has existed for billions of years, is one of the earliest energy-converting systems. "All of our food, our energy sources (gasoline, coal) -- everything is a product of some ancient photosynthetic activity," says Kálmán. But he adds that the main reason researchers are turning to these ancient natural systems is because they are carbon neutral and use resources that are in abundance: sun, carbon dioxide and water. Researchers are using nature's battery to inspire more sustainable, human-made energy converting systems. For a peek into the future of these technologies, Kálmán points to medical applications and biocompatible batteries. Imagine batteries made of enzymes and other biological molecules. These could be used to, for example, monitor a patient from the inside post-surgery. Unlike traditional batteries that contain toxic metals, biocompatible batteries could be left inside the body without causing harm. "We're far from that right now but these devices are currently being explored and developed," says Kálmán. "We have to take things step by step but, hopefully, we'll get there one day in the not-too-distant future." This research was funded by a grant from the Natural Sciences and Engineering Research Council of Canada.

New fuel cell in line for European award

Thomas Ruyant is a French competitive sailor, with many races and several international victories under his belt. He needs a very light, long- lasting energy source on his yacht. He relies on a type of methanol-powered fuel cell to power all his navigational electronics, and in harsh conditions.

These lighter fuel cells are produced in a laboratory in Munich, Germany. They are designed to power, over several months, small electronic devices, like for example small home appliances or gadgets for travel or leisure, and are 80 per cent lighter than conventional batteries.

Behind the invention of these lighter fuel cells is German chemical and mechanical engineer Manfred Stefener. He and his team have created a very compact and portable fuel cell battery.

The idea that Manfred Stefener had in the 1990s was basically to replace hydrogen, the traditional fuel cells power source, with methanol. Methanol is an alcohol used, for example, in antifreeze and windshield-wiper fluid. Four times denser than hydrogen, it requires less storage space and therefore reduces battery weight. Stefener’s team successfully managed to miniaturize the fuel cell structure, making it more commercially viable.

“Methanol is a liquid fuel with a very high energy density, and can be transported very easily, so it’s much easier for smaller fuel cells to use methanol instead of hydrogen to be transported, to fill in small cartridges or to provide very long run times for fuel cells,” says Stefener.

Stefener has also created yet another kind of fuel cell device powered by natural gas, destined for domestic power and heat in homes. He says this device can make large savings on our energy bills and reduce CO2 emissions by 40 percent.

“The fuel cell works like this,” he explains. “It takes normal natural gas from the grid, and produces electricity, which covers about 40 to 60 per cent of the total electricity demand of a typical European home and it covers also like the full warm water demand of these homes.”

Stefener, aged 42, is among the nominees for the European Inventor Award, organized by the European Patent Office, which is taking place in June in Copenhagen. After his studies, he decided that the use of hydrogen in big, heavy fuel cells was completely unrealistic:

“During my PHD thesis, that I started in 1997 here at the technical University of Munich, I realized that hydrogen powered cars, that everybody wanted at that time, were not ready for commercialization, because they were too expensive and the hydrogen infrastructure was not there. So my idea was to make fuel cells for smaller devices with a factor of thousand lower power.”

euronews:
“How did you feel after having discovered this new technology?”

“Today you can see that methanol fuel cells, I have invented now 15 years ago, is the first commercial product in fuel cell market, and of course this is a very satisfying feeling that today people are really using products based on the invention I made many many years ago,” he smiles.

Stefener is convinced that fuel cells can spawn a range of new ideas and applications to help satisfy the ever growing energy needs of our society.

3D Printing Revolution

3D printing technology is progressing rapidly, and some experts say it could revolutionise the way objects are made in the future.

An object is scanned – or designed on computer modelling software – then sliced up, into many thousands of tiny layers, which are then printed out, eventually forming a solid three dimensional product.

Lifesaving Nano Nose Smells Cancer

Prostate cancer is one of the leading killers in men. One reason for this is that so few go for a preventive, but invasive, medical check up. The late detection of prostate cancer often means the removal of a part or all of the organ, but now there is some clever technology which should aid early detection.

At a research facility in Barcelona a ‘new artificial nose’ is being developed, which scientists say could actually smell cancer molecules. The nano-technology is being developed by European research project BOND .


Professor Josep Samitier of the University of Barcelona explained what they are hoping to detect: “When we smell flowers or perfume, or when we eat, we receive important information in the form of chemicals. This chemical information exists and develops also when an illness occurs, for example in the case of cancer or other diseases.”

The highly sensitive nano-nose examines the urine of cancer patients and the results are promising.

According to researchers, in a few years, it might be possible to provide doctors with a small device which reliably shows whether the patient’s urine is contaminated with cancer cells or not.

The artificial smelling system relies on several hundred nanometric biosensors, which can detect even the tiniest number of cancer cells.

This non-invasive detection method could be a milestone in the fight against prostate cancer.

Researchers are still in the trial phase but the potential for saving lives is enormous.

Introducing the Leap

Leap represents an entirely new way to interact with your computers. It's more accurate than a mouse, as reliable as a keyboard and more sensitive than a touchscreen. For the first time, you can control a computer in three dimensions with your natural hand and finger movements.

New Lithium-Air Battery Technology

New Battery Technology with Higher Energy Density than Any Existing Battery

Lightweight batteries that can deliver lots of energy are crucial for a variety of applications - for example, improving the range of electric cars. For that reason, even modest increases in a battery's energy-density rating - a measure of the amount of energy that can be delivered for a given weight - are important advances. Now a team of researchers at MIT has made significant progress on a technology that could lead to batteries with up to three times the energy density of any battery that currently exists. Doctoral student Yi-Chun Lu holds an experimental lithium-air battery that was used for testing at MIT. Photo: Patrick Gillooly Yang Shao-Horn, an MIT associate professor of mechanical engineering and materials science and engineering, says that many groups have been pursuing work on lithium-air batteries, a technology that has great potential for achieving great gains in energy density. But there has been a lack of understanding of what kinds of electrode materials could promote the electrochemical reactions that take place in these batteries. Lithium-oxygen (also known as lithium-air) batteries are similar in principle to the lithium-ion batteries that now dominate the field of portable electronics and are a leading contender for electric vehicles. But because lithium-air batteries use lightweight porous carbon electrodes and oxygen drawn from a flow of air to take the place of heavy solid compounds used in lithium-ion batteries, the batteries themselves can be much lighter. That's why leading companies, including IBM and General Motors, have committed to major research initiatives on lithium-air technology. In a paper published this week in the journal Electrochemical and Solid-State Letters, Shao-Horn, along with some of her students and visiting professor Hubert Gasteiger, reported on a study showing that electrodes with gold or platinum as a catalyst show a much higher level of activity and thus a higher efficiency than simple carbon electrodes in these batteries. In addition, this new work sets the stage for further research that could lead to even better electrode materials, perhaps alloys of gold and platinum or other metals, or metallic oxides, and to less expensive alternatives. Doctoral student Yi-Chun Lu, lead author of the paper, explains that this team has developed a method for analyzing the activity of different catalysts in the batteries, and now they can build on this research to study a variety of possible materials. "We'll look at different materials, and look at the trends," she says. "Such research could allow us to identify the physical parameters that govern the catalyst activity. Ultimately, we will be able to predict the catalyst behaviors. " One issue to be dealt with in developing a battery system that could be widely commercialized is safety. Lithium in metallic form, which is used in lithium-air batteries, is highly reactive in the presence of even minuscule amounts of water. This is not an issue in current lithium-ion batteries because carbon-based materials are used for the negative electrode. Shao-Horn says the same battery principle can be applied without the need to use metallic lithium; graphite or some other more stable negative electrode materials could be used instead, she says, leading to a safer system. A number of issues must be addressed before lithium-air batteries can become a practical commercial product, she says. The biggest issue is developing a system that keeps its power through a sufficient number of charging and discharging cycles for it to be useful in vehicles or electronic devices. Researchers also need to look into details of the chemistry of the charging and discharging processes, to see what compounds are produced and where, and how they react with other compounds in the system. "We're at the very beginning" of understanding exactly how these reactions occur, Shao-Horn says. Gholam-Abbas Nazri, a researcher at the GM Research & Development Center in Michigan, calls this research "interesting and important," and says this addresses a significant bottleneck in the development of this technology: the need find an efficient catalyst. This work is "in the right direction for further understanding of the role of catalysts," and it "may significantly contribute to the further understanding and future development of lithium-air systems," he says. While some companies working on lithium-air batteries have said they see it as a 10-year development program, Shao-Horn says it is too early to predict how long it may take to reach commercialization. "It's a very promising area, but there are many science and engineering challenges to be overcome," she says. "If it truly demonstrates two to three times the energy density" of today's lithium-ion batteries, she says, the likely first applications will be in portable electronics such as computers and cell phones, which are high-value items, and only later would be applied to vehicles once the costs are reduced.