May
12
A Hint of Hydrogen Hope
May 12, 2009 | 1 Comment
A hydrogen rich compound discovered by Yu Lin, lead author of a paper describing the work and a graduate student in geological and environmental sciences published this week in the online edition of Proceedings of the National Academy of Sciences might become a path to a hydrogen economy.
The “newly” discovered material is a high-pressure form of ammonia borane, NH3BH3, a solid material that is already rich with its own hydrogen. By working with the ammonia borane at high pressure in an atmosphere artificially enriched with hydrogen, the scientists were able to ratchet up the hydrogen content of the material by roughly 50 percent.
The new compound, called ammonia borane-hydrogen, contains more than triple the amount the Department of Energy has set a target for hydrogen-powered vehicles. The DOE has set a goal of an on-board storage system able to store 9 percent of vehicle mass, by weight, of hydrogen in 2015. Lin said, “Including the hydrogen already stored in ammonia borane, this new material can store around 30 percent (of its own) weight in total.”
But the problem is the temperature and pressure for the materials. The process used to get the added hydrogen into the ammonia borane has to take place at a minimum pressure that is approximately 60,000 times the usual pressure at the surface of the Earth. That’s, if the press release writer got it right, would be 60,000 atmospheres. Any way it’s figured, those are extreme pressures.
Lin said, “For energy applications, we need to stabilize the material near ambient conditions.” Today, most hydrogen-powered machines use either compressed hydrogen gas or liquid hydrogen, which needs to be maintained at high pressure or very low temperature. Those methods have major safety concerns in the case of compressed hydrogen and require significant energy for cooling in the case of liquid hydrogen.
The hydrogen rich compound discovered by Stanford researchers could potentially be a solution for helping overcome one of the biggest hurdles to using hydrogen for fuel -namely, how do you stuff enough hydrogen into a volume that is small enough to be portable and practical for powering a car for example?
Currently no material satisfies all of the requirements for on-board fuel storage for hydrogen-powered vehicles. “If the material can be stabilized at or near ambient conditions with a large amount of hydrogen content, then I think it will be very promising,” Lin said.
Stanford Scientists Yu Lin on left and Wendy Mao.
Lin, who is working with Wendy Mao, assistant professor of geological and environmental sciences at Stanford and a co-author of the paper, are looking at several potential ways to help stabilize the compound under normal temperature and pressure conditions. One idea Lin offers is that there might be some “alternative chemical paths, like adding some catalyst to try to stabilize the system.”
If Lin and Mao come up with a storage medium that’s more practical, ammonia borane could move one step closer to becoming an everyday storage material for hydrogen. It’s interesting to see the lengths that research is going to in containing hydrogen. All driven by scientists’ and environmentalists’ dream of powering cars with oxygen from the air and hydrogen from the fuel cell, while pumping out only water from the exhaust pipe. It’s a great dream I’ll grant, but the pressure conditions the ladies are handling is by itself a cause to pause.
Also, Wendy Mao is an assistant professor in the photon science department at SLAC National Accelerator Laboratory at Stanford. Another participating is co-author Ho-kwang Mao, senior staff scientist at the Geophysical Laboratory at the Carnegie Institution of Washington.
The major advantage to this research is the guidance it can provide for the storage solution hunt. Hydrogen being the smallest atom is a devil to contain so locking it up by some means suggests the only practical solution of any appreciable amount of time. The surprise is that a molecule like ammonium borane already so hydrogen rich can be induced to take on more. Granted the pressures are high but it’s a step, and it may prove to be a highly instructive one.
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