Published: March 09, 2006
Progress Made in Using Hydrogen as Fuel for Cars, Electronics
New material can store large amounts of hydrogen, researchers say
In the push to develop hydrogen fuel cells to power cars, cell phones and other devices, one of the biggest challenges has been finding ways to store large amounts of hydrogen at the right temperatures and pressures.
Now, researchers at the University of California-Los Angeles (UCLA) and the University of Michigan have demonstrated the ability to store large amounts of hydrogen at the right pressure, and they have ideas about how to store hydrogen at ambient temperatures.
The research was funded by the U.S. National Science Foundation, the U.S. Department of Energy (DOE) and BASF, a global chemical company based in Germany, according to a March 6 UCLA press release.
DOE estimates that a practical fuel will require concentrations of at least 6.5 percent hydrogen, but the chemists have achieved concentrations of 7.5 percent - nearly three times as higher than as previously reported - but at a very low temperature (minus 196 degrees Celsius).
"Using a new material," said UCLA chemistry professor Omar Yaghi, who conducted the research with colleagues at the University of Michigan, "we have identified a clear path for how to get above 7 percent of the material's weight in hydrogen."
The work could lead to a hydrogen fuel that powers cars as well as laptop computers, cellular phones, digital cameras and other electronic devices.
The research involves a class of materials whose rod-like components the chemists can change at will, according to a March 6 UCLA press release.
The materials, which Yaghi invented in the early 1990s, are called metal-organic frameworks (MOFs) that are like submicroscopic scaffolds made of linked rods, a structure that maximizes the surface area.
MOFs have been described as crystal sponges. They have pores - nanoscale (1-100 nanometers; a nanometer is one billionth of a meter) openings in which Yaghi and colleagues can store gases that usually are difficult to store and transport.
MOFs can be made highly porous to increase their storage capacity; 1 gram of a MOF has the surface area of a football field.
Yaghi's laboratory has made more than 500 MOFs that have a variety of properties and structures. The researchers now want to achieve the 7.5 percent hydrogen concentration at a temperature closer to that of the surrounding air. Such ambient temperatures are 0-45 degrees Celsius.
MOFs can be made from low-cost ingredients, such as zinc oxide, a common ingredient in sunscreen, and terephthalate, a substance found in plastic beverage bottles.
How would hydrogen work in devices like cell phones, laptop computers and digital cameras?
"Instead of a battery," Yaghi said, "one would have a medium such as MOF that stores hydrogen and releases it into a fuel cell."
Hydrogen, when burned, produces only water, which is harmless to the environment. Stored in MOFs, hydrogen is physically absorbed, and it is easy to take the hydrogen out and put it back in without much energy cost, he said.
The challenge, he said, has been to store enough hydrogen for an automobile to run for 300-400 miles without refueling.
In previous research, Yaghi has shown that MOFs store large amounts of carbon dioxide, one of the greenhouse gases, at ambient conditions, a development relevant to preventing carbon dioxide emissions from power plants and automobiles from reaching the atmosphere.
Yaghi and colleagues also reported that MOFs can store large amounts of methane, another greenhouse gas.
"We have materials that exceed the DOE requirements for methane," he said, "and we think we can apply the same sort of strategy for hydrogen storage."
The full text of the UCLA press release is available on the university's Web site.
Source: U.S. Department of State
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