(Press-News.org) Inexpensive hydrogen for automotive or jet fuel may be possible by mimicking photosynthesis, according to a Penn State materials chemist, but a number of problems need to be solved first.
"We are focused on the hardest way to make fuel," said Thomas Mallouk, Evan Pugh Professor of Materials Chemistry and Physics. "We are creating an artificial system that mimics photosynthesis, but it will be practical only when it is as cheap as gasoline or jet fuel."
Splitting water into hydrogen and oxygen can be done in a variety of ways, but most are heavily energy intensive. The resultant hydrogen, which can be used to fuel vehicles or converted into a variety of hydrocarbons, inevitably costs more than existing fossil-based fuels.
While some researchers have used solar cells to make electricity or use concentrated solar heat to split water, Mallouk's process uses the energy in blue light directly. So far, it is much less efficient than other solar energy conversion technologies.
The key to direct conversion is electrons. Like the dyes that naturally occur in plants, inorganic dyes absorb sunlight and the energy kicks out an electron. Left on its own, the electron would recombine creating heat, but if the electrons can be channeled -- molecule to molecule -- far enough away from where they originate, the electrons can reach the catalyst and split the hydrogen from the oxygen in water.
"Currently, we are getting only 2 to 3 percent yield of hydrogen," Mallouk told attendees today (Feb. 19) at the annual meeting of the American Association for the Advancement of Science. "For systems like this to be useful, we will need to get closer to 100 percent," he added.
But recombination of electrons is not the only problem with the process. The oxygen-evolving end of the system is a chemical wrecking ball and this means the lifetime of the system is currently limited to a few hours.
"The oxygen side of the cell is making a strong oxidizing agent and the molecules near can be oxidized," said Mallouk. "Natural photosynthesis has the same problem, but it has a self-repair mechanism that periodically replaces the oxygen-evolving complex and the protein molecules around it."
So far, the researchers do not have a fix for the oxidation, so their catalysts and other molecules used in the cell structure eventually degrade, limiting the life of the solar fuel cell.
Currently, the researchers are using only blue light, but would like to use the entire visible spectrum from the sun. They are also using expensive components – a titanium oxide electrode, a platinum dark electrode and iridium oxide catalyst. Substitutions for these are necessary, and other researchers are working on solutions. A Massachusetts Institute of Technology group is investigating cobalt and nickel catalysts, and at Yale University and Princeton University they are investigating manganese.
"Cobalt and nickel don't work as well as iridium, but they aren't bad," said Mallouk. "The cobalt work is spreading to other institutions as well."
While the designed structure of the fuel cell directs many of the electrons to the catalyst, most of them still recombine, giving over their energy to heat rather than chemical bond breaking. The manganese catalysts in photosystem II -- the photosynthesis system by which plants, algae and photosynthetic bacteria evolve oxygen -- are just as slow as ours, said Mallouk. Photosystem II works efficiently by using an electron mediator molecule to make sure there is always an electron available for the dye molecule once it passes its current electron to the next molecule in the chain.
"We could slow down major recombination in the artificial system in the same way," said Mallouk. "Electron transfer from the mediator to the dye would effectively outrun the recombination reaction."
Currently the system uses only one photon at a time, but a two-photon system, while more complicated, would be more effective in using the full spectrum of sunlight.
Mallouk's main goal now is to track all the energy pathways in his cell to understand the kinetics. Once he knows this, he can model the cells and adjust portions to decrease energy loss and increase efficiency.
INFORMATION:
END
University of Rochester optics professor Jannick Rolland has developed an optical technology that provides unprecedented images under the skin's surface. The aim of the technology is to detect and examine skin lesions to determine whether they are benign or cancerous without having to cut the suspected tumor out of the skin and analyze it in the lab. Instead, the tip of a roughly one-foot-long cylindrical probe is placed in contact with the tissue, and within seconds a clear, high-resolution, 3D image of what lies below the surface emerges.
Rolland will be presenting ...
The global scientific community is capable of policing its own behavior and should resist creation of a central oversight body to enforce 'universal standards' that may have unintended consequences, a renowned physicist and director of the Energy Institute at the University of Texas at Austin said Saturday.
Speaking at the American Association for the Advancement of Science (AAAS) Science Without Borders meeting in Washington, D.C., Raymond L Orbach, Ph.D., singled out several elements contained in the "Singapore Statement of Research Integrity" (www.singaporestatement.org) ...
Washington (Thursday, February 17) — According to University of Toronto speech-language pathologist Luc De Nil, the beat could be revealing such things as how children master one of the most complex tasks of all – speech.
"The rapid and precise muscle movements of speech must be the most intricate, yet poorly understood, of all the sensory-motor skills," says De Nil.
De Nil's interest in finger-tapping came out of his group's previous work on adults who stutter. His team discovered that they have problems in acquiring new and unusual tapping sequences and not just speech. ...
ANN ARBOR, Mich.---The Mimosa plant, which folds its leaves when they're touched, is inspiring a new class of adaptive structures designed to twist, bend, stiffen and even heal themselves. University of Michigan researchers are leading their development.
Mechanical engineering professor Kon-Well Wang will present the team's latest work Feb. 19 at the American Association for the Advancement of Science's 2011 Annual Meeting in Washington D.C. He will also speak at a news briefing earlier that day. Wang is the Stephan P. Timoshenko Collegiate Professor of Mechanical Engineering ...
Using the super-sharp radio "vision" of astronomy's most precise telescope, scientists have extended a directly-measured "yardstick" three times farther into the cosmos than ever before, an achievement with important implications for numerous areas of astrophysics, including determining the nature of Dark Energy, which constitutes 70 percent of the Universe. The continent-wide Very Long Baseline Array (VLBA) also is redrawing the map of our home Galaxy and is poised to yield tantalizing new information about extrasolar planets, among many other cutting-edge research projects.
The ...
At this year's American Association for the Advancement of Science (AAAS) meeting in Washington, D.C., February 17 to 21, Caltech researchers will present topics ranging from solar and renewable energy solutions to the latest advancements in bioengineering. Caltech's Alice S. Huang, AAAS president, will deliver the President's Address at the opening ceremony, highlighting this year's AAAS theme, "Science Without Borders."
Friday, February 18
Session: Portraits of the California Energy System in 2050: Cutting Emissions by 80 Percent
Title: The Future of Game-Changing ...
Arthroscopic rotator cuff repair is highly effective and provides durable results five years after surgery, according to a large, prospective study by Hospital for Special Surgery investigators. The study also surprisingly revealed that the rotator cuff has the ability to heal even when early imaging studies have found a defect at the site of repair. The research will be presented at the upcoming American Shoulder and Elbow Surgeons (ASES) 2011 Specialty Day meeting, to be held Feb. 19 in San Diego, Calif., following the annual meeting of the American Academy of Orthopaedic ...
Sports hernias are commonly found in individuals with a mechanical disorder of the hip and can be resolved with surgery to fix the hip disorder alone in some cases, according to a recent study. The research, conducted by investigators at Hospital for Special Surgery, will be presented at the American Orthopedic Society for Sports Medicine 2011 Specialty Day meeting, held Feb. 19 in San Diego following the annual meeting of the American Academy of Orthopaedic Surgeons.
"If individuals have symptoms of athletic pubalgia otherwise known as sports hernia, doctors should carefully ...
A panel of scientists speaking today at the annual meeting of the American Association for the Advancement of Science (AAAS) unveiled new research and models demonstrating how climate change could increase exposure and risk of human illness originating from ocean, coastal and Great Lakes ecosystems, with some studies projecting impacts to be felt within 30 years.
"With 2010 the wettest year on record and third warmest for sea surface temperatures, NOAA and our partners are working to uncover how a changing climate can affect our health and our prosperity," said Jane ...
This release is available in French.
Washington — New evidence bolsters the notion that deep saline groundwaters in South Africa's Witwatersrand Basin may have remained isolated for many thousands, perhaps even millions, of years.
The study, recently accepted for publication in Chemical Geology, found the noble gas neon dissolved in water in three-kilometre deep crevices.
The unusual neon profile, along with the high salinities and some other unique chemical signatures, is very different from anything seen in molten fluid and gases rising from beneath the Earth's ...
