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Carbon Nanotubes Go Back Inside Fuel Cells

Researchers have tried to apply carbon nanotubes to fuel cells for some time now. At first there was hope that carbon nanotubes would help fuel cells better store hydrogen. That dream was dashed and then later resurrected. There has also been the idea that carbon nanotubes could be used as a cheaper alternative to expensive catalysts within fuel cells

I suppose those are worthy areas of pursuit, but the two main issues that have prevented fuel cells from gaining wider adoption—at least in the area of powering automobiles—are the costs of isolating hydrogen and building an infrastructure that would deliver that hydrogen to the automobiles. The issue of isolating hydrogen has taken precedence of late in nanotech/fuel cell research both at the commercial level and at research labs

But now researchers from Stanford University are again looking at how carbon nanotubes could replace more expensive catalysts used in oxidizing the hydrogen at the anode within the fuel cell.

Hongjie Dai, a professor of chemistry at Stanford and co-author of the study, believes that a cheaper oxidizing catalyst will facilitate wider adoption of fuel cells.

"Platinum is very expensive and thus impractical for large-scale commercialization," says Dai in the Stanford press release covering the research. "Developing a low-cost alternative has been a major research goal for several decades."

Well, if you could develop a catalyst for this purpose that was essentially free, it still wouldn’t usher in a hydrogen economy any time soon. But I suppose it couldn’t hurt.

The research, which was published in the May 27th online edition of the journal Nature Nanotechnology, showed that when the outer walls of a multi-walled carbon nanotube (MWNT) were shredded—and the inner walls left intact—the catalytic ability of the MWNTs were enhanced while maintaining good electrical conductivity.

What I find most intriguing about the research is the potential to use these imperfect MWNTs for metal-air batteries. The researchers hint at this, though they have yet to fully explore the possibilities.

"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 says in the Stanford press release. "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."

I think it's all together possible that researchers at IBM and the US national labs who have been working on metal-air batteries for years now might be somewhat more interested in this line of research than fuel-cell manufacturers.

IBM Pushes Atomic Force Microscopy to Its Limits

Back in 2009 IBM pushed the boundaries of surface microscopy when they developed a technique for noncontact atomic force microscopy (AFM) that enabled the resolving of single atoms in molecules.  Since then IBM has been working on this foundational work to develop a Kelvin probe force microscopy (KPFM) technique that enabled the first imaging of the charge distribution within a molecule

Now the team, based in Zurich, that have been at the forefront of this research have just completed some collaborative research with the Royal Society of Chemistry (RSC) and the University of Warwick in which they have imaged the synthetic molecule Olympicene (named after its resemblance to the five-ring design of the Olympic symbol) to the point where they could not only image individual hydrogen atoms but also manipulate them. Here's a video describing the research:

While IBM’s noncontact AFM had shown the ability to image hydrogen atoms previously, this latest research made that capability more concrete, according to Leo Gross, Scientist, at IBM Research Zurich.

A unique feature of the IBM-developed AFM technique is that it can image individual molecules whereas other techniques require that the molecules be collected into an aggregate crystal form. But perhaps even more importantly, what this line of research has demonstrated rather clearly is that they can use the tip of the AFM to induce reactions, such as forming a bond or extracting an atom.

This can be seen most clearly in the images the researchers created of the Olympicene molecule. In one you can see the bonds between the links of the molecule is much brighter. This is where there are two hydrogen atoms attach to the olympicene molecule.  In another image you can see that same site is no longer as bright because they have removed one of the hydrogen atoms, creating what they dubbed the Olympicene radical.

While Gross believes that the imaging and manipulation of hydrogen atoms marks the limits in scale for this technique, there are still things at this size they would like to investigate.  “We would like to look at things such as the adsorption, bonding and bonding angles, position, distances,” says Gross.

In addition to this line of research, Gross sees a great deal of potential is the KPFM technique. “We want to use this ability to image charge distribution and charge separation to study molecules for organic solar cells where charge separation is very important, and also for molecular electronics, such as single-molecule devices, which have a functionality depending on single electrons. The combined techniques of AFM and KPFM give us a very good tool to study these single-electron devices.”

Solid-State Dye-Sensitized Solar Cell Matches Performance of Grätzel Cell

In the past, I have tried to dispel the myth that nanotechnology could be waved over alternative energy applications to make them suddenly much more economically viable than they have been. In these efforts, I have even gone so far as to question the reasoning of Nobel Laureates in Economics on why we are not further along in the development of photovoltaics. 

This is not to say that nanotechnology is not improving various alternative energy solutions, in particular photovoltaics. But the process of bringing these technologies to market is much slower than many people seem willing to tolerate and their announcements should be taken with a grain of salt...and patience.

So, it is with some cautious optimism I alert you to research coming out of Northwestern University in which the researchers claim to have developed a new type of solar cell that has all the benefits of the Grätzel cell (or dye-sensitized solar cell (DSSC)) without the short life expectancy.

“The Grätzel cell is like having the concept for the light bulb but not having the tungsten wire or carbon material,” explains one of the researchers, Mercouri Kanatzidis, in the university’s press release covering the development. “We created a robust novel material that makes the Grätzel cell concept work better. Our material is solid, not liquid, so it should not leak or corrode.”

This is not the first time that researchers have attempted to find a replacement for the organic liquid that makes up the electrolyte in DSSCs. But previous attempts have resulted in solar cells with poor energy conversion efficiency. To overcome this Kanatzidis and his colleague Robert P.H. Chang used a thin-film compound made up of cesium, tin and iodine, which serves as a p-type direct bandgap semiconductor. Details of the new material can be found in their recently published article in Nature. The result is the Northwestern solar cell reached a conversion efficiency of 10.2 percent, in the neighborhood of the 11 to 12 percent reached by the best performing Grätzel cell.

“This is the first demonstration of an all solid-state dye-sensitized solar cell system that promises to exceed the performance of the Grätzel cell,” Chang is quoted as saying in the same university press release. “Our work opens up the possibility of these materials becoming state of the art with much higher efficiencies than we’ve seen so far.”

While the university press release quotes Chang as saying that their solar cell is “inexpensive,” there were no accompanying cost calculations to back up the claim. Last year, when I spoke to Michael Grätzel, the discoverer of the DSSC, we talked not of lifecycle costs, but about boosting the conversion efficiency of the DSSC. But perhaps more important than conversion efficiency, the key metric for Grätzel was the kWh price.

From my discussion with Grätzel in Budapest last May:

When it came to the question of conversion efficiency, Dr. Grätzel seemed resigned to the percentage game that seems to exist, but believed that kilowatt hour (kWh) to price was a more significant metric.

“We have to play the game. We have to go and have our efficiencies validated by an accredited PV calibration laboratory. We cannot create a different world where we just say we are the best,” he said. “We are living exactly with the standards that silicon has set in terms of efficiency and stability.

“But, on the other hand, it is true that when it comes to the advantages we should also play those up as well,” he said. He added that under certain outdoor exposures DSSC will already out perform silicon in the key metric of kWh price

“In the end, what we would really like to see is kWh price used as a metric in addition to peak watt price. The peak watt price is a good standard but when it comes to outdoor applications it often does not reflect reality such as the performance under cloudy conditions and the drop of conversion efficiency with temperature encountered by silicon solar cells,” he said.

It may be that the Northwestern researchers have developed a solar cell that when you calculate life cycle costs (presumably since they last longer they don't have to be replaced as often) has a better kWh cost than any other solar cells on the market, including the Grätzel cell. But I would like to see those calculations before I pronounce this as the replacement for any solar cell.

Graphene Adds Rustproofing Steel to Its List of Applications

While graphene continues its seemingly inexorable march towards electronics applications, I've also been chronicling some of the attempts to use graphene in applications outside of electronics

Along these lines, researchers at the University of Buffalo have now developed a use for graphene that rustproofs steel in a less toxic way than other methods. 

Sarbajit Banerjee, PhD, an assistant professor, and Robert Dennis, a PhD student, determined that graphene’s hydrophobic and conductive properties made it an ideal candidate for preventing corrosion. According to Banerjee in an Phys.org article, graphene actually stunts electro-chemical reactions that transform iron into iron oxide, otherwise known as rust.

Graphene would replace the environmentally unfriendly hexavalent chromium in the rustproofing process of steel. This chemical has brought on a slew of environmental regulations that have taken their toll on the bottom line of some steel manufacturers.

In the video below, Robert Dennis explains a bit about the technology and also the inspiration to look at finding a more environmentally friendly approach to rustproofing steel.

“Our product can be made to work with the existing hardware of many factories that specialize in chrome electroplating, including job shops in Western New York that grew around Bethlehem Steel," explains Banerjee in the Phys.org article. "This could give factories a chance to reinvent themselves in a healthy way in a regulatory environment that is growing increasingly harsh when it comes to chromium pollution."

To add a double irony to the story, the inspiration for this line of research came from the hope of help turning around the local steel business that's part of the broader Great Lakes industrial area known as the Rust Belt, and while the domestic industry is suffering largely due to outsourcing, the steel company that supported much of the research was India-based Tata Steel.

Nanoparticles and Sunshine Split Water Molecule for Hydrogen Gas

Just in case you believed that companies announce some nano-related research for a bit of buzz and then abandon the research, I am here to tell you that is not always the case. Back in March, I covered Santa Barbara, Calif.-based Hypersolar’s grand proposal for producing hydrogen gas in a zero-carbon process from wastewater.

To Hypersolar’s credit they have decided to chronicle their achievements (and perhaps failures) in a development process in which there are no guarantees of success. In the video below, Tim Young, CEO of HyperSolar, narrates a proof of concept prototype that demonstrates the effectiveness of the process. As Young explains, an inexpensive plastic baggy was filled with wastewater from a paper mill and on the bottom of the baggy is a small-scale solar device that is protected with Hypersolar’s polymer coating. Add sunlight, and hydrogen comes bubbling up.

“A big hurdle in using a solar to fuel conversion process is the stabilization of the semiconductor material against photocorrosion,” explains Young in a company press release announcing the development. “Our development of an efficient and low cost protective polymer coating that also allows good electrical conductivity is a significant achievement in our development of a cost effective means for using the power of the Sun to extract renewable hydrogen from water.”

Young suggests in the video that the small-scale solar device used in the prototype will be replaced with Hypersolar’s nanoparticles, which can be mass-produced and lead to large-scale production of hydrogen gas.

“The implications of our technology may be world changing,” claims Young in another company press release. “If we can successfully complete the development of a low cost, highly efficient solar powered water-splitting nanoparticle, we can use readily available seawater, runoff water, river water, or wastewater, to produce large quantities of hydrogen fuel to power the world. When the hydrogen fuel is used in fuel cells or combustion, clean water (pure H2O) returns back to the Earth. HyperSolar is making steady technical progress to enable this vision.”

It should be interesting to see whether this mimicking of photosynthesis will be able to compete with processes that simply replace platinum with a nanomaterial as a catalyst in the tried and tested electrocatalytic processes for producing hydrogen gas. 

Samsung Creates a Graphene Transistor with a Band Gap and Electron Mobility

 

Getting a graphene-based transistor to turn on and off has typically meant sacrificing its incredible electron mobility in the bargain. And the truth of it is that graphene's electron mobility—which is 200 times greater than that of silicon—is what has made it such an attractive alternative in a post silicon world.

Lately, research has been focused on coming up with different varieties of graphene better suited to electronics applications. A so-called “graphene monoxide (GMO)” looks promising, and an isotopically engineered graphene could find use in heat management applications for electronics. 

Researchers at the Samsung Advanced Institute of Technology have taken a different approach. Instead of altering the graphene, they have re-engineered the basic operating principles of digital switches.

They developed a three-terminal active device (described in the journal Science) in which the key feature is a “an atomically sharp interface between graphene and hydrogenated silicon.” The device, capable of switching on and off via a Schottky barrier that controls the flow of current by changing its height, does so without the graphene losing any of its precious electron mobility. 

Whenever you demonstrate a transistor, you get the usual refrain of: “Let me know when you make a simple logic circuit.” Ask and it shall be given. The Samsung researchers have reported the most basic logic gate (inverter) and logic circuits (half-adder) as part of their research, and demonstrated a basic operation (adding).

With nine patents already filed around this research, maybe this will be the way forward in bringing graphene to commercial electronics.

Nano Devices Based on Block Copolymers Could Lead to Next Generation of Computing

 

As far back as 2007 in the ITRS roadmap, the use of block copolymers has been targeted for reducing chip size. Since then they have been used to push the possibilities of self-assembled photoresists  as well as improve insulation within chips. 

During this period, researchers at CRANN, the nanoscience institute based at Trinity College Dublin—which partners with University College Cork (UCC)—along with researchers from the University of Wisconsin and Intel’s Researchers in Residence based in CRANN—namely, Professor Mick Morris of UCC—have been characterizing the block copolymer to better understand its self-assembling properties.

The results from the research, which were published in the journal Nanoscale, has demonstrated a method for fabricating large-area arrays of silicon nanowires through directed self-assembly of block copolymer nanopatterns that can be easily integrated into current manufacturing techniques.

In a press release issued by the Science Foundation of Ireland, Morris commented,  “The potential of our research is extremely exciting and reflects many years of hard work. This is the first time that anyone has demonstrated that large areas of nano-electronic devices can be developed in this fashion and highlights a pathway to commercial applications. I am looking forward to exploring commercial opportunities to further advance our work.”

Those associated with the project believe that the development could revolutionize the manufacturing of silicon chips and lead to a new generation of computers and real-time 3D video processing.

These types of claims are pretty regular in press releases covering this kind of research. In this case, however, given how deeply involved Intel was in the research one can’t help but give it a bit more credence than usual.

Graphene Combined with Quantum Dots Result in Efficient Photodetector

Graphene research has been turning increasingly towards its potential in optoelectronic applications.  This is not a surprise because graphene’s optical properties are as astounding as its electrical conductivity capabilities.

But just as graphene has the glaring Achilles Heel in electronics applications of lacking a band gap, it also suffers a couple of fatal flaws in optoelectronics. For example, while nearly every single photon the material absorbs generates an electron-hole pair, it doesn’t really absorb that much light. According to some estimates, it absorbs less than 3 percent of the photons falling on it.

So, researchers at the Institute of Photonic Sciences (ICFO) in Barcelona, Spain thought about the possibility of combining graphene with quantum dots to see if they couldn’t overcome graphene’s shortcomings.

The research, which was published in the journal Nature Nanotechnology last week,  demonstrated that the combination of the two nanomaterials did the trick. Instead of absorbing just 3 percent of the light that hits it, the graphene/quantum dot hybrid material is capable of absorbing 25 percent of the light falling on it. This new absorption capability is due to the quantum dots, and when you combine that with the graphene’s ability to make every photon into an electron-hole pair, the potential for generating current is significant.

"In our work, we managed to successfully combine graphene with semiconducting nanocrystals to create complete new functionalities in terms of light sensing and light conversion to electricity," Gerasimos Konstantatos, co-leader of the team at the Institute of Photonic Sciences (ICFO) in Barcelona, told physicsworld.com. "In particular, we are looking at placing our photodetectors on ultrathin and flexible substrates or integrating the devices into existing computer chips and cameras," added co-leader Frank Koppens in the same article.

The researchers offer a range of applications for the graphene-and-quantum-dot combination, including digital cameras and sensors. But it seems the researchers seem particularly excited about one application in particular. They expect the material will be used for night-vision technologies in automobiles—an application I have never heard trotted out before in relation to nanotech.

"We expect that most cars will be equipped with night-vision systems in the near future and our arrays could form the basis of these," Koppens told physicsworld.com.

Nanostructured Silicon Anodes Improve, But Is It Enough for EVs?

Lithium-ion (Li-ion) batteries are ubiquitous but flawed, especially for electric vehicle applications. The problem has been poor charge life. But researchers have shown that if you replace the graphite on the anodes with silicon, the charge can be increased by a factor of ten. Problem is that after a few charge-discharge cycles the silicon cracks and becomes inoperable from the expansion and contraction of the material.

One solution: nanostructured silicon anodes that improve on the traditional silicon variety in this area of charge-discharge cycles. While there’s been improvement from silicon’s poor performance, the nanostructured variety still doesn’t measure up to plain old graphite in this regard.

That's a shame, because silicon anodes just crush graphite when it comes charge life. So, if there were a way to get silicon to work, it would offer some considerable benefits to Li-ion batteries, and nanotechnology has been the prayer. At least one commercial interest believes that the nano-based solution has already been developed for enabling silicon anodes to survive a large number of charge-discharge cycles.

Now research, led by Yi Cui of Stanford, who holds the distinction of having the most cited paper at ACS journal Nano Letters over the past 10 years, has come up with a nanostructured silicon capable of 6,000 cycles while maintaining 85% of its capacity.

That sounds good…for lithium-ion batteries, but Cui demonstrated just last year that potassium or sodium ions in place of the lithium variety can create batteries capable of 40,000 cycles while maintaining 83% of its charge. The issue there was that they had the cathode sorted but hadn’t yet developed the anode.

Then there's the issue of applications. The sodium- or potassium-based ion battery was targeted for large-scale energy storage on the electrical grid. Again, the Li-ion battery Cui and his colleagues has developed is being targeted for electric vehicle applications.

Cui himself started a company, Amprius, in which he was going to use his silicon nanowire anode technology with the aim of doubling the energy density of Li-ion batteries. I hope the company succeeds, but even if you achieve a doubling of energy density in the Li-ion battery you still only get to 400Wh/kg for powering vehicles. According to Stephen Chu, Li-ion batteries will need to get to 1000Wh/kg to really be competitive with fossil fuel-powered vehicles. Why can’t powering laptops be good enough for these batteries?

Nanocatalyst Splits Water Molecules at a Fraction the Cost of Platinum

Nanotechnology-based solutions for improving fuel cells have fallen a bit short of expectations. So  recent research has focused instead on using nanotech to produce hydrogen gas for existing fuel cells more cheaply and efficiently.

Some of these solutions—like those from University of California, San Diego, or those of Angela Belcher of MIT—have been aimed at breaking down a water molecule into its constituent parts of hydrogen and oxygen by replicating photosynthesis. This is really cutting edge stuff and pretty far removed from the process currently used to create hydrogen gas, which involves applying electricity to water in the presence of a catalyst.

One of the main problems with this current method has been the cost of platinum, which is the best material to serve as a catalyst for the process. With platinum going for about $50,000 per kilogram, it’s pretty clear why this gets to be a very expensive process.

To address this issue researchers at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have developed a new nanomaterial that can duplicate the capabilities of platinum at a fraction of the cost.

“We wanted to design an optimal catalyst with high activity and low costs that could generate hydrogen as a high-density, clean energy source,” said Brookhaven Lab chemist Kotaro Sasaki in a press release covering the research. “We discovered this exciting compound that actually outperformed our expectations.”

The researchers—whose results were initially published online yesterday in the journal Angewandte Chemie International Edition—determined early on that nickel can take the reactive place of platinum, but didn’t have the same electron density. While the introduction of metallic molybdenum to the nickel improved its reactivity, it still wasn’t up to platinum standards.

Sasaki and his colleagues believed that they could push the nickel-molybdenum material up to platinum levels by applying nitrogen, based on the understanding that this had been done with bulk materials. They weren’t quite sure what to expect when you applied the nitrogen to nanoscale nickel-molybdenum but they suspected that it would change the structure of the material into discrete, sphere-like nanostructures. That’s not what they got.

To the surprise of the researchers, the infusing of nitrogen with nickel-molybdenum material produced two-dimensional nanosheets.

“Despite the fact that metal nitrides have been extensively used, this is the first example of one forming a nanosheet,” said research associate Wei-Fu Chen, the paper’s lead author in the Lab’s press release. “Nitrogen made a huge difference – it expanded the lattice of nickel-molybdenum, increased its electron density, made an electronic structure approaching that of noble metals, and prevented corrosion.”

While the researchers are realistic in their understanding that this new catalyst doesn’t answer all the issues facing the production of hydrogen gas, it does have the advantage over other solutions in that it can be directly substituted into current processes that use platinum as a catalyst to cut the costs dramatically. Whether this will usher in the age of the hydrogen economy is impossible to say, but it's a step in the right direction.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
Editor
Dexter Johnson
Madrid, Spain
 
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Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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