New Solvents May Lead to Better Biofuels
|Reproduced from here. For personal use. No part of the article is mine.
Molten salts used as solvents may provide a stepping stone toward cheaper, more environmentally friendly biofuels, researchers said this month.
One of the biggest challenges biofuel producers face is breaking down energy-containing plant material into simple sugars that can be fermented into fuel. It’s particularly difficult to break down the tough cellulose in material like wood chips and switchgrass, which could otherwise produce more energy-efficient ethanol than corn.
A majority of ethanol producers use strong chemicals or heat to dissolve the plant material. But molten salts — also called ionic liquids — may provide a better alternative, researchers said at an Australian symposium on ionic liquids. The liquids are made up of highly charged atoms called ions, and the forces exerted by those ions make the liquid an ideal solvent.
“Ionic liquids are the enabling technology to ‘crack’ biomass efficiently and economically,” said Robin Rogers, a chemistry professor at the University of Alabama. “This is really the key to any biomass product.”
Scientists have known about the solvent properties of ionic liquids for decades. But only in the past few years have the liquids begun to move from the laboratory to factories and processing plants for use in processes such as textile and paper manufacturing.
Chemical company BASF owns a patent on an ionic liquid-based cellulose processing method developed by Rogers, and is trying to apply that method on a commercial scale. It’s already working with AlterVia Fuels, an early stage technology development company, on a smaller-scale version.
Mark Lenhart, COO of AlterVia Fuels said, “By using ionic liquids we have a lower energy input and can use the existing infrastructure [of ethanol refineries], and use fewer raw materials to produce biofuel.”
Current chemical solvents generate waste and can take 48 hours to separate the cellulose. Unlike ionic liquids, they cannot be reused, so refineries must continually repurchase them. They also result in ethanol containing water that must be removed, according to Matthias Maase, manager of business development at BASF. The new method works faster, doesn’t generate toxic waste and produces a purer ethanol with less water, he said.
“What we have observed about ionic liquids is that they grab the water and release the ethanol, which results in a purer ethanol, an estimated 20 percent gain in purity,” Maase said. He estimated that if a biofuel refinery produces 10,000 gallons of ethanol a day they could increase capacity to 12,500 gallons with this new technology.
But not everyone believes that ionic liquids will be the answer to most ethanol producers needs. At the moment, they are more expensive to purchase than the chemicals already used to dissolve cellulose, and they cannot replace other costly chemicals needed in the biofuel refining process.
Although ionic liquids are generally considered less toxic than traditional solvents, some researchers also question their environmental benefits. Imidazolium salts — the main ingredients in ionic liquids — do not evaporate, meaning they create no air pollutants, but there is still research being done on their toxicity in aqueous environments, said Ziding Zhang of China Agricultural University.
“In the area of cellulose for biofuel, the ionic liquids used are still within the traditional ionic liquid family, i.e. composed of mostly by imidazolium derivatives that have minor-to-moderate toxicities to the environment and human beings,” he said.
Peter Scammells, a chemistry professor at Monash University, has also questioned the green properties of ionic liquids. In a 2005 article, he pointed out that there are still problems with recycling ionic liquids, and maintaining their purity and effectiveness.
Meanwhile, laboratory research on the liquids continues. Scientists at the Joint Bioenergy Institute see ionic liquids as a next step in producing ethanol from wood and grasses — materials that are much more abundant and cheaper than corn.
“Every process in development goes through a few roadblocks. Corn may not be the best solution for biofuels. I’m very confident that we will be able to produce fuel from biomass with lower carbon emissions associated with production when compared to oil petroleum,” Blake Simmons says, a scientist and researcher at Joint Bioenergy Institute.
And the University of Alabama’s Rogers believes the technology could be useful in producing other biofuels, such as butanol. “Ionic liquids will allow the cracking of biomass in an economical manner for a number of new businesses. The focus on ethanol is shortsighted,” he said.
New Solar Energy Material Captures Every Color
Of The Rainbow
Reproduced from here. I do not claim ownership to any of the material found here.
ScienceDaily (Oct. 17, 2008) — Researchers have created a new material that overcomes two of the major obstacles to solar power: it absorbs all the energy contained in sunlight, and generates electrons in a way that makes them easier to capture.
Ohio State University chemists and their colleagues combined electrically conductive plastic with metals including molybdenum and titanium to create the hybrid material.
“There are other such hybrids out there, but the advantage of our material is that we can cover the entire range of the solar spectrum,” explained Malcolm Chisholm, Distinguished University Professor and Chair of the Department of Chemistry at Ohio State.
Sunlight contains the entire spectrum of colors that can be seen with the naked eye — all the colors of the rainbow. What our eyes interpret as color are really different energy levels, or frequencies of light. Today’s solar cell materials can only capture a small range of frequencies, so they can only capture a small fraction of the energy contained in sunlight.
This new material is the first that can absorb all the energy contained in visible light at once.
The material generates electricity just like other solar cell materials do: light energizes the atoms of the material, and some of the electrons in those atoms are knocked loose.
Ideally, the electrons flow out of the device as electrical current, but this is where most solar cells run into trouble. The electrons only stay loose for a tiny fraction of a second before they sink back into the atoms from which they came. The electrons must be captured during the short time they are free, and this task, called charge separation, is difficult.
In the new hybrid material, electrons remain free much longer than ever before.
To design the hybrid material, the chemists explored different molecular configurations on a computer at the Ohio Supercomputer Center. Then, with colleagues at National Taiwan University, they synthesized molecules of the new material in a liquid solution, measured the frequencies of light the molecules absorbed, and also measured the length of time that excited electrons remained free in the molecules.
They saw something very unusual. The molecules didn’t just fluoresce as some solar cell materials do. They phosphoresced as well. Both luminous effects are caused by a material absorbing and emitting energy, but phosphorescence lasts much longer.
To their surprise, the chemists found that the new material was emitting electrons in two different energy states — one called a singlet state, and the other a triplet state. Both energy states are useful for solar cell applications, and the triplet state lasts much longer than the singlet state.
Electrons in the singlet state stayed free for up to 12 picoseconds, or trillionths of a second — not unusual compared to some solar cell materials. But electrons in the triplet state stayed free 7 million times longer — up to 83 microseconds, or millionths of a second.
When they deposited the molecules in a thin film, similar to how they might be arranged in an actual solar cell, the triplet states lasted even longer: 200 microseconds.
“This long-lived excited state should allow us to better manipulate charge separation,” Chisholm said.
At this point, the material is years from commercial development, but he added that this experiment provides a proof of concept — that hybrid solar cell materials such as this one can offer unusual properties.
The project was funded by the National Science Foundation and Ohio State’s Institute for Materials Research.
Chisholm is working with Arthur J. Epstein, Distinguished University Professor of chemistry and physics; Paul Berger, professor of electrical and computer engineering and physics; and Nitin Padture, professor of materials science and engineering to develop the material further. That work is part of the Advanced Materials Initiative, one Ohio State’s Targeted Investment in Excellence (TIE) programs.
The TIE program targets some of society’s most pressing challenges with a major investment of university resources in programs with a potential for significant impact in their fields. The university has committed more than $100 million over the next five years to support 10 high-impact, mostly interdisciplinary programs.
Co-authors on the PNAS paper from Ohio State included: Gotard Burdzinski, a postdoctoral researcher; Yi-Hsuan Chou, a postdoctoral researcher; Florian Fiel, a former postdoctoral researcher; Judith Gallucci, a senior research associate; Yagnaseni Ghosh, a graduate student; Terry Gustafson, a professor; Yao Liu, a postdoctoral researcher; Ramkrishna Ramnauth, a former postdoctoral researcher; and Claudia Turro, a professor; all of the Department of Chemistry. They collaborated with Pi-Tai Chou and Mei-Lin Ho of National Taiwan Universit
My input: What IS the darn material?
Article reproduced verbatim from here. This is for my personal record of news that interest me and I do not claim ownership of any of the matter reproduced.
UA inventor Joseph Kennedy receives 100th patent Wednesday, October 22, 2008
Akron, OH — World-renowned scientist, researcher and inventor Dr. Joseph Kennedy, distinguished professor of polymer science and chemistry at The University of Akron, recently received his 100th U.S. patent — no small accomplishment in the world of innovation. In fact, the U.S. Patent and Trademark Office says an achievement of this magnitude is extremely rare. Kenneth Preston, UA’s associate vice president of research and director of technology transfer, notes that many of the world’s finest inventors have no more than 10 patents to their names. Kennedy’s work has indirectly saved millions of lives. His invention of the polystyrene-polyisobutylene-polystyrene block copolymer and thermoplastic elastomer is the basis of a biocompatible polymer coating on Boston Scientific’s TAXUS® drug-eluting cardiovascular stent, which has been implanted in about 5 million patients worldwide. While the stent does its work to open clogged coronary arteries, Kennedy’s polymer coating time-releases drugs and replaces the bare metal stent of bygone days with one more compatible with human tissue. Kennedy’s 100th patent is U.S. Patent 7,388,065, “Process for Preparing Siloxane Compounds,” which involves an improved method for producing high-performance silicone rubbers. Such polymers could be used in range of applications, including industrial, household and medical products
Natural Dyes Adsorbed on TiO2 Nanowire for Photovoltaic Applications: Enhanced Light Absorption and Ultrafast Electron Injection
Sheng Meng, Jun Ren, and Efthimios Kaxiras*
Nano Lett., 8 (10), 3266–3272, 2008. 10.1021/nl801644d
Web Release Date: September 13, 2008
Copyright © 2008 American Chemical Society
We investigate the electronic coupling between a TiO2 nanowire and a natural dye sensitizer, using state-of-the-art time-dependent first-principles calculations. The model dye molecule, cyanidin, is deprotonated into the quinonoidal form upon adsorption on the wire surface. This results in its highest occupied molecular orbital (HOMO) being located in the middle of the TiO2 bandgap and its lowest unoccupied molecular orbital (LUMO) being close to the TiO2 conduction band minimum (CBM), leading to greatly enhanced visible light absorption with two prominent peaks at 480 and 650 nm. We find that excited electrons are injected into the TiO2 conduction band within a time scale of 50 fs with negligible electron−hole recombination and energy dissipation, even though the dye LUMO is located 0.1−0.3 eV lower than the CBM of the TiO2 nanowire.
Meryl D. Stoller, Sungjin Park, Yanwu Zhu, Jinho An, and Rodney S. Ruoff*
Nano Lett., 8 (10), 3498–3502, 2008. 10.1021/nl802558y
Web Release Date: September 13, 2008
Copyright © 2008 American Chemical Society
The surface area of a single graphene sheet is 2630 m2/g, substantially higher than values derived from BET surface area measurements of activated carbons used in current electrochemical double layer capacitors. Our group has pioneered a new carbon material that we call chemically modified graphene (CMG). CMG materials are made from 1-atom thick sheets of carbon, functionalized as needed, and here we demonstrate in an ultracapacitor cell their performance. Specific capacitances of 135 and 99 F/g in aqueous and organic electrolytes, respectively, have been measured. In addition, high electrical conductivity gives these materials consistently good performance over a wide range of voltage scan rates. These encouraging results illustrate the exciting potential for high performance, electrical energy storage devices based on this new class of carbon material.
Consolidating interesting news for personal use. Disclaimer – the information is reproduced directly from the parent site with no personal inputs whatsoever.
Sun + Water = Fuel
With catalysts created by an MIT chemist, sunlight can turn water into hydrogen. If the process can scale up, it could make solar power a dominant source of energy.
By Kevin Bullis
“I’m going to show you something I haven’t showed anybody yet,” said Daniel Nocera, a professor of chemistry at MIT, speaking this May to an auditorium filled with scientists and U.S. government energy officials. He asked the house manager to lower the lights. Then he started a video. “Can you see that?” he asked excitedly, pointing to the bubbles rising from a strip of material immersed in water. “Oxygen is pouring off of this electrode.” Then he added, somewhat cryptically, “This is the future. We’ve got the leaf.”
What Nocera was demonstrating was a reaction that generates oxygen from water much as green plants do during photosynthesis–an achievement that could have profound implications for the energy debate. Carried out with the help of a catalyst he developed, the reaction is the first and most difficult step in splitting water to make hydrogen gas. And efficiently generating hydrogen from water, Nocera believes, will help surmount one of the main obstacles preventing solar power from becoming a dominant source of electricity: there’s no cost-effective way to store the energy collected by solar panels so that it can be used at night or during cloudy days.
Solar power has a unique potential to generate vast amounts of clean energy that doesn’t contribute to global warming. But without a cheap means to store this energy, solar power can’t replace fossil fuels on a large scale. In Nocera’s scenario, sunlight would split water to produce versatile, easy-to-store hydrogen fuel that could later be burned in an internal-combustion generator or recombined with oxygen in a fuel cell. Even more ambitious, the reaction could be used to split seawater; in that case, running the hydrogen through a fuel cell would yield fresh water as well as electricity.
Storing energy from the sun by mimicking photosynthesis is something scientists have been trying to do since the early 1970s. In particular, they have tried to replicate the way green plants break down water. Chemists, of course, can already split water. But the process has required high temperatures, harsh alkaline solutions, or rare and expensive catalysts such as platinum. What Nocera has devised is an inexpensive catalyst that produces oxygen from water at room temperature and without caustic chemicals–the same benign conditions found in plants. Several other promising catalysts, including another that Nocera developed, could be used to complete the process and produce hydrogen gas.
Nocera sees two ways to take advantage of his breakthrough. In the first, a conventional solar panel would capture sunlight to produce electricity; in turn, that electricity would power a device called an electrolyzer, which would use his catalysts to split water. The second approach would employ a system that more closely mimics the structure of a leaf. The catalysts would be deployed side by side with special dye molecules designed to absorb sunlight; the energy captured by the dyes would drive the water-splitting reaction. Either way, solar energy would be converted into hydrogen fuel that could be easily stored and used at night–or whenever it’s needed.
Nocera’s audacious claims for the importance of his advance are the kind that academic chemists are usually loath to make in front of their peers. Indeed, a number of experts have questioned how well his system can be scaled up and how economical it will be. But Nocera shows no signs of backing down. “With this discovery, I totally change the dialogue,” he told the audience in May. “All of the old arguments go out the window.”
The Dark Side of Solar
Sunlight is the world’s largest potential source of renewable energy, but that potential could easily go unrealized. Not only do solar panels not work at night, but daytime production waxes and wanes as clouds pass overhead. That’s why today most solar panels–both those in solar farms built by utilities and those mounted on the roofs of houses and businesses–are connected to the electrical grid. During sunny days, when solar panels are operating at peak capacity, homeowners and companies can sell their excess power to utilities. But they generally have to rely on the grid at night, or when clouds shade the panels.
This system works only because solar power makes such a tiny contribution to overall electricity production: it meets a small fraction of 1 percent of total demand in the United States. As the contribution of solar power grows, its unreliability will become an increasingly serious problem.
If solar power grows enough to provide as little as 10 percent of total electricity, utilities will need to decide what to do when clouds move in during times of peak demand, says Ryan Wiser, a research scientist who studies electricity markets at Lawrence Berkeley National Laboratory in Berkeley, CA. Either utilities will need to operate extra natural-gas plants that can quickly ramp up to compensate for the lost power, or they’ll need to invest in energy storage. The first option is currently cheaper, Wiser says: “Electrical storage is just too expensive.”
But if we count on solar energy for more than about 20 percent of total electricity, he says, it will start to contribute to what’s called base load power, the amount of power necessary to meet minimum demand. And base load power (which is now supplied mostly by coal-fired plants) must be provided at a relatively constant rate. Solar energy can’t be harnessed for this purpose unless it can be stored on a large scale for use 24 hours a day, in good weather and bad.
In short, for solar to become a primary source of electricity, vast amounts of affordable storage will be needed. And today’s options for storing electricity just aren’t practical on a large enough scale, says Nathan Lewis, a professor of chemistry at Caltech. Take one of the least expensive methods: using electricity to pump water uphill and then running the water through a turbine to generate electricity later on. One kilogram of water pumped up 100 meters stores about a kilojoule of energy. In comparison, a kilogram of gasoline stores about 45,000 kilojoules. Storing enough energy this way would require massive dams and huge reservoirs that would be emptied and filled every day. And try finding enough water for that in places such as Arizona and Nevada, where sunlight is particularly abundant.
Batteries, meanwhile, are expensive: they could add $10,000 to the cost of a typical home solar system. And although they’re improving, they still store far less energy than fuels such as gasoline and hydrogen store in the form of chemical bonds. The best batteries store about 300 watt-hours of energy per kilogram, Lewis says, while gasoline stores 13,000 watt-hours per kilogram. “The numbers make it obvious that chemical fuels are the only energy-dense way to obtain massive energy storage,” Lewis says. Of those fuels, not only is hydrogen potentially cleaner than gasoline, but by weight it stores much more energy–about three times as much, though it takes up more space because it’s a gas.
The challenge lies in using energy from the sun to make such fuels cheaply and efficiently. This is where Nocera’s efforts to mimic photosynthesis come in.
In real photosynthesis, green plants use chlorophyll to capture energy from sunlight and then use that energy to drive a series of complex chemical reactions that turn water and carbon dioxide into energy-rich carbohydrates such as starch and sugar. But what primarily interests many researchers is an early step in the process, in which a combination of proteins and inorganic catalysts helps break water efficiently into oxygen and hydrogen ions.
The field of artificial photosynthesis got off to a quick start. In the early 1970s, a graduate student at the University of Tokyo, Akira Fujishima, and his thesis advisor, Kenichi Honda, showed that electrodes made from titanium dioxide–a component of white paint–would slowly split water when exposed to light from a bright, 500-watt xenon lamp. The finding established that light could be used to split water outside of plants. In 1974, Thomas Meyer, a professor of chemistry at the University of North Carolina, Chapel Hill, showed that a ruthenium-based dye, when exposed to light, underwent chemical changes that gave it the potential to oxidize water, or pull electrons from it–the key first step in water splitting.
Ultimately, neither technique proved practical. The titanium dioxide couldn’t absorb enough sunlight, and the light-induced chemical state in Meyer’s dye was too transient to be useful. But the advances stimulated the imaginations of scientists. “You could look ahead and see where to go and, at least in principle, put the pieces together,” Meyer says.
Over the next few decades, scientists studied the structures and materials in plants that absorb sunlight and store its energy. They found that plants carefully choreograph the movement of water molecules, electrons, and hydrogen ions–that is, protons. But much about the precise mechanisms involved remained unknown. Then, in 2004, researchers at Imperial College London identified the structure of a group of proteins and metals that is crucial for freeing oxygen from water in plants. They showed that the heart of this catalytic complex was a collection of proteins, oxygen atoms, and manganese and calcium ions that interact in specific ways.
“As soon as we saw this, we could start designing systems,” says Nocera, who had been trying to fully understand the chemistry behind photosynthesis since 1984. Reading this “road map,” he says, his group set out to manage protons and electrons somewhat the way plants do–but using only inorganic materials, which are more robust and stable than proteins.
Initially, Nocera didn’t tackle the biggest challenge, pulling oxygen out from water. Rather, “to get our training wheels,” he began with the reverse reaction: combining oxygen with protons and electrons to form water. He found that certain complex compounds based on cobalt were good catalysts for this reaction. So when it came time to try splitting water, he decided to use similar cobalt compounds.
Nocera knew that working with these compounds in water could be a problem, since cobalt can dissolve. Not surprisingly, he says, “within days we realized that cobalt was falling out of this elaborate compound that we made.” With his initial attempts foiled, he decided to take a different approach. Instead of using a complex compound, he tested the catalytic activity of dissolved cobalt, with some phosphate added to the water to help the reaction. “We said, let’s forget all the elaborate stuff and just use cobalt directly,” he says.
The experiment worked better than Nocera and his colleagues had expected. When a current was applied to an electrode immersed in the solution, cobalt and phosphate accumulated on it in a thin film, and a dense layer of bubbles started forming in just a few minutes. Further tests confirmed that the bubbles were oxygen released by splitting the water. “Here’s the luck,” Nocera says. “There was no reason for us to expect that just plain cobalt with phosphate, versus cobalt being tied up in one of our complexes, would work this well. I couldn’t have predicted it. The stuff that was falling out of the compounds turned out to be what we needed.
“Now we want to understand it,” he continues. “I want to know why the hell cobalt in this thin film is so active. I may be able to improve it or use a different metal that’s better.” At the same time, he wants to start working with engineers to optimize the process and make an efficient water-splitting cell, one that incorporates catalysts for generating both oxygen and hydrogen. “We were really interested in the basic science. Can we make a catalyst that works efficiently under the conditions of photosynthesis?” he says. “The answer now is yes, we can do that. Now we’ve really got to get to the technology of designing a cell.”
Catalyzing a Debate
Nocera’s discovery has garnered a lot of attention, and not all of it has been flattering. Many chemists find his claims overstated; they don’t dispute his findings, but they doubt that they will have the consequences he imagines. “The claim that this is the answer for artificial photosynthesis is crazy,” says Thomas Meyer, who has been a mentor to Nocera. He says that while Nocera’s catalysts “could prove technologically important,” the advance is “a research finding,” and there’s “no guarantee that it can be scaled up or even made practical.”
Many critics’ objections revolve around the inability of Nocera’s lab setup to split water nearly as rapidly as commercial electrolyzers do. The faster the system, the smaller a commercial unit that produced a given amount of hydrogen and oxygen would be. And smaller systems, in general, are cheaper.
The way to compare different catalysts is to look at their “current density”–that is, electrical current per square centimeter–when they’re at their most efficient. The higher the current, the faster the catalyst can produce oxygen. Nocera reported results of 1 milliamp per square centimeter, although he says he’s achieved 10 milliamps since then. Commercial electrolyzers typically run at about 1,000 milliamps per square centimeter. “At least what he’s published so far would never work for a commercial electrolyzer, where the current density is 800 times to 2,000 times greater,” says John Turner, a research fellow at the National Renewable Energy Laboratory in Golden, CO.
Other experts question the whole principle of converting sunlight into electricity, then into a chemical fuel, and then back into electricity again. They suggest that while batteries store far less energy than chemical fuels, they are nevertheless far more efficient, because using electricity to make fuels and then using the fuels to generate electricity wastes energy at every step. It would be better, they say, to focus on improving battery technology or other similar forms of electrical storage, rather than on developing water splitters and fuel cells. As Ryan Wiser puts it, “Electrolysis is [currently] inefficient, so why would you do it?”
The Artificial Leaf
Michael Grätzel, however, may have a clever way to turn Nocera’s discovery to practical use. A professor of chemistry and chemical engineering at the École Polytechnique Fédérale in Lausanne, Switzerland, he was one of the first people Nocera told about his new catalyst. “He was so excited,” Grätzel says. “He took me to a restaurant and bought a tremendously expensive bottle of wine.”
In 1991, Grätzel invented a promising new type of solar cell. It uses a dye containing ruthenium, which acts much like the chlorophyll in a plant, absorbing light and releasing electrons. In Grätzel’s solar cell, however, the electrons don’t set off a water-splitting reaction. Instead, they’re collected by a film of titanium dioxide and directed through an external circuit, generating electricity. Grätzel now thinks that he can integrate his solar cell and Nocera’s catalyst into a single device that captures the energy from sunlight and uses it to split water.
If he’s right, it would be a significant step toward making a device that, in many ways, truly resembles a leaf. The idea is that Grätzel’s dye would take the place of the electrode on which the catalyst forms in Nocera’s system. The dye itself, when exposed to light, can generate the voltage needed to assemble the catalyst. “The dye acts like a molecular wire that conducts charges away,” Grätzel says. The catalyst then assembles where it’s needed, right on the dye. Once the catalyst is formed, the sunlight absorbed by the dye drives the reactions that split water. Grätzel says that the device could be more efficient and cheaper than using a separate solar panel and electrolyzer.
Another possibility that Nocera is investigating is whether his catalyst can be used to split seawater. In initial tests, it performs well in the presence of salt, and he is now testing it to see how it handles other compounds found in the sea. If it works, Nocera’s system could address more than just the energy crisis; it could help solve the world’s growing shortage of fresh water as well.
Artificial leaves and fuel-producing desalination systems might sound like grandiose promises. But to many scientists, such possibilities seem maddeningly close; chemists seeking new energy technologies have been taunted for decades by the fact that plants easily use sunlight to turn abundant materials into energy-rich molecules. “We see it going on all around us, but it’s something we can’t really do,” says Paul Alivisatos, a professor of chemistry and materials science at the University of California, Berkeley, who is leading an effort at Lawrence Berkeley National Laboratory to imitate photosynthesis by chemical means.
But soon, using nature’s own blueprint, human beings could be using the sun “to make fuels from a glass of water,” as Nocera puts it. That idea has an elegance that any chemist can appreciate–and possibilities that everyone should find hopeful.