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MOF-74 is a unique carbon metal compound, which can store hydrogen unpressurized at densities higher than solid hydrogen. The green atoms are zinc ions, while the white/gray atoms are carbon.  (Source: NIST)
Carbon based material offers hydrogen storage densities better than solid hydrogen without pressure

With the rise in interest of a so-called "hydrogen-economy" and switching to vehicles burning hydrogen or using it in fuel cells, a critical challenge has become how to store hydrogen.  Many experts think that in order for hydrogen-powered vehicles to be competitive in terms of range with modern gas vehicles, hydrogen will need to be stored at densities greater than that of liquid hydrogen.  Such super compression brings up complex problems of safety and costs.

A recent DailyTech article describes how scientists are developing plans to store hydrogen in carbon fullerene structures, such as "buckyballs".  Now, the National Institute of Standards and Technology’s Center for Neutron Research (NCNR) demonstrated a promising new storage technique using another exotic class of carbon materials.

NIST, the University of Maryland and the California Institute of Technology all collaborated in the study, which examined metal-organic frameworks (MOFs).  This class of compounds is considered highly promising as it can store and release hydrogen easily with simple changes in conditions.  This might allow for a fuel pump-style approach one day.  MOFs also are advantageous in that they don't require as high temperatures to release hydrogen.  Other materials frequently require between temperatures ranging from 110 to 500 C before they release the hydrogen.

The team focused most of their research on MOF-74, a porous crystalline powder developed at the University of California at Los Angeles.  The compound is curiously shaped with carbon arranged in straw like molecules with columns of zinc ions running along the insides of the tubes.  The straws are densely packed and form a powdery material.  Just one gram of the substance has as much surface area as a tennis court, due to its unique design.

The structure packs hydrogen in amazingly well.  Researchers discovered that at 77 K (-196 C), MOF-74 absorbs more hydrogen than any non-pressurized material to date.  The material packs hydrogen more densely than even a block of solid hydrogen.  The researchers used a mixture of neutron scattering and gas adsorption techniques to come to these findings.

NCNR scientist Craig Brown states that the team remains unsure exactly what makes MOF-74 so great at grabbing hydrogen.  He says the team is speculating it may be due to some interactions with the zinc ions.  Brown enthuses about MOF-74's promise stating, "When we started doing experiments, we realized the metal interaction doesn’t just increase the temperature at which hydrogen can be stored, but it also increases the density above that in solid hydrogen.  This is absolutely the first time this has been encountered without having to use pressure."

The temperature needed for storage in MOF-74 is easily obtainable using cheaper liquid nitrogen.  This is favorable in comparison with solid hydrogen, which requires lower temperatures of -269 C.  The researchers hope further studies will allow them to modify the material or find similar materials that will allow storage at even higher temperatures.  This will allow for the removal of refrigeration and/or insulation systems, lowering the production costs and improving fuel economy.

The new research was funded by the Department of Energy's Hydrogen Sorption Center of Excellence.


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Interesting, but...
By masher2 (blog) on 4/4/2008 4:16:06 PM , Rating: 5
While I am, as always, excited about such research, it's important to remember nature has already given us a means of efficiently storing hydrogen within a carbon framework --hydrocarbons thenselves. Done properly, the entire process is both carbon-neutral and fully renewable:

Step 1: condense CO2 from atmosphere and extract hydrogen from water using electrolysis or thermolysis
Step 2: Add energy to synthesize artificial gasoline and/or other petroleum products.

Given that any hydrogen-based economy is going to require mass amounts of energy from some other source, I wonder just how effective these exotic methods of hydrogen storage are, compared to good old hydrocarbons themselves




RE: Interesting, but...
By AphexTwin1111 on 4/4/2008 4:32:55 PM , Rating: 4
It would be nice to see some reference to Yaghi who not only made these MOF structures but also coined the term MOF in the first place. And in addition, synthesising hydrocarbons from cabron dioxide is no mean feat. simply functionalising methane is hard enough. afaik there are no catalytic systems not requiring INCREDIBLY large amounts of energy to generate usable products [besides PS1+2 in plants].

i was also curious as to why daily tech was reporting on fullerene's as hydrogen storage, yaghi has made compounds whose structure incorporates buckyballs and the mof elements and if memory serves they were less effective at storing hydrogen [% by weight] than the pure mof type structure. either way at present these are the way forward in terms of hydrogen storage.


RE: Interesting, but...
By kattanna on 4/4/2008 4:52:28 PM , Rating: 2
whats gets me is that this method, using cold temps, seems more energy inefficient then using pressure.

pressure can be contained without energy expenditure using a strong enough container.

cold storage ALWAYS requires energy to maintain.

seems a step in the wrong direction to me.


RE: Interesting, but...
By teldar on 4/5/2008 11:28:52 AM , Rating: 2
I think the point is that it is stable at low pressure and normal temperatures once the hydrogen is absorbed into the material.
The problem with pressure is the weight of the tank. You want a 300lb tank to store enough hydrogen to go 15 miles. And the materials which require high pressure to absorb hydrogen also frequently require high temperature. If this stuff is able to be stored at normal pressures and temperatures and can easily be induced to give off its hydrogen, it sounds like it is an ideal medium.

T


RE: Interesting, but...
By geddarkstorm on 4/4/2008 11:39:17 PM , Rating: 2
Well, it kinda depends on the density they got the hydrogen to. All the article says is denser than solid hydrogen, which is only 0.088g/cm^3. Now, gasoline is around 0.7g/cm^3, and if we assume the gasoline is made mostly of octane (C8H18), then that gives gasoline a hydrogen density of ~0.117g/cm^3. Quite a bit better than solid hydrogen. It's too bad the article doesn't say how dense they got the hydrogen, though probably not that dense.

At any case, the difference here is that all this compound they made is doing is binding up the hydrogen. No energy is involved in that binding except in getting the conditions right to favor that binding, and in making the compound itself. If this is more useful or not than the method you listed (which is a smart one), I can't tell without knowing how much energy goes into making this compound verses producing hydrocarbons from CO2 (though it takes quite a bit of energy for the latter, it doesn't sound too hard from what I've read).


RE: Interesting, but...
By TheSpaniard on 4/6/2008 2:40:15 PM , Rating: 3
the energy required to do his method is very high compared to what you get out...

for that you might as well build a battery powered car


RE: Interesting, but...
By MrBlastman on 4/7/2008 10:47:02 AM , Rating: 2
You were thinking exactly what I was - these roundabout methods of creating carbon structures is essentially a high-tech exercise in fabricating what we already have in petroleum.

I am very curious as to what the hydrogen density will be compared with traditional oil. They talk about density etc., but do not give us actual per unit breakdowns -

i.e. 80% Carbon, 10% Hydrogen, 10% metals.

Perhaps these carbon storage units are hyper-efficient compared with say petroleum? Perhaps they allow storage of say 80% Hydrogen and 15% Carbon and 5% Metal? This would be a tremendous energy advantage over current petroleum.

The thing that concerns me is the introduction of metals into the fuel. We are already aware of the effects of say Carbon on our atmosphere (this won't solve the CO2 emissions problem), but by introducing metals into the equation, you have a whole different thing to worry about.

You also have to take into consideration the quantity of metals being used versus the total amount available globally.

I'll continue to believe that our resources should be spent further away from liquid fuels and closer towards non-liquid alternatives (not even batteries which are very pollutive to produce in their current form).


More what if science?
By randomly on 4/4/2008 5:51:15 PM , Rating: 2
At least this is more interesting than the mental masturbation of the Buckyball hydrogen storage. That was just bathroom wall scribbling ...' well if you COULD put hydrogen inside a buckeyball and I have this computer program I can calculate how much pressure I can put inside a buckeyball till it breaks...it will hold less than half the hydrogen than the same weight of gasoline'. It's like calculating how big a piece of the sun you'd have to put in a car to drive it 100,000 miles. Interesting perhaps, but totally useless info. They offered no mechanism to get the hydrogen in efficiently, nor any way to get it out efficiently. Teleportation perhaps.

At least this one sounds possibly useful. It will all depend on if you can get the hydrogen in and out without a huge energy cost, and it's economical and portable. It's going to have to get close to compressed gas at 12% energy cost. And in the end all this will end up moot because Hydrogen powered cars are just too inefficient and too costly to compete with gas and electric. As they say 'Hydrogen is the fuel of the future, and always will be'.




RE: More what if science?
By TheOtherBubka on 4/4/2008 9:13:53 PM , Rating: 2
Totally agree randomly regarding the theoretical 'buckyball' approach. Furthermore, due to the DOE's goal of the hydrogen storage material storing 6% by weight of hydrogen, for this MOF material, you are going to need roughly 2 molecules of hydrogen per zinc atom plus roughly another 1.5 molecule of H2 per carbon ring in the carbon skeleton. That's a lot of hydrogen. The only question that remains is how much this MOF stored per unit weight whether 'theoretically' or for real.


RE: More what if science?
By snownpaint on 4/7/2008 2:55:32 PM , Rating: 2
Most of the time new ideas start as theoretical, math thought experiments, or suggested ideas, then someone figures out the applied science that goes into it making it a working system.. Like Photoelectric effects, which was first introduced by Planck as a purely mathematical manipulation. Later it was experimentally proven, then engineered and currently used on the calculator sitting on your desk to the satellite circling the earth.

despite claims, technology is reaching levels never imagined 30 years ago.. From the computer you are typing on to the sublimated printing of your clothing tags. A simple change in how something makes a process easier, or the increase in resources ( electricity, oil, ect) can change everything that was thought impossible or economically infeasible.


RE: More what if science?
By snownpaint on 4/7/2008 2:55:32 PM , Rating: 2
Most of the time new ideas start as theoretical, math thought experiments, or suggested ideas, then someone figures out the applied science that goes into it making it a working system.. Like Photoelectric effects, which was first introduced by Planck as a purely mathematical manipulation. Later it was experimentally proven, then engineered and currently used on the calculator sitting on your desk to the satellite circling the earth.

despite claims, technology is reaching levels never imagined 30 years ago.. From the computer you are typing on to the sublimated printing of your clothing tags. A simple change in how something makes a process easier, or the increase in resources ( electricity, oil, ect) can change everything that was thought impossible or economically infeasible.


RE: More what if science?
By randomly on 4/7/2008 6:14:18 PM , Rating: 2
I'm well aware how ideas start out, but many of these things like the buckyball hydrogen storage are written up and sold to the public as if they promise miracles just around the corner, when in actuality they are no closer to reality than teleportation.

Two major things seem to drive this speculative science reported as fact. One is the never ending hunger for reporters to find something to write about that will draw readership and make sales. The second is the desperate hunger of scientists (usually university based) to get grants, or to justify the grants they have.

Personally I have no sympathy for the press people who will jazz up, distort, and sell anything they can get their hands on. I've got a soft spot for researchers who need money though, as long as it doesn't get too out of hand. They do need to be held accountable. As you pointed out you can never predict where the end results of real basic research will take you, but it almost always pays off. Just as long as you take care to pick the scammers out of the wheat.


Whoa
By geddarkstorm on 4/4/2008 2:36:57 PM , Rating: 2
Now that's just awesome. Sounds like all you need to do to release the hydrogen is raise the temperature--then just shunt the slow releasing gas or liquid to a fuel cell.

I wonder what other applications such an exotic compounds could have. Drug delivery? Pollution clean up?




RE: Whoa
By root mean sq on 4/4/2008 2:56:16 PM , Rating: 5
ice cold beeer!!!!!!!! ...or various non-alcoholic drinks

who wouldn't to mod a cooling unit storing hydrogen fuel to chill drinks in their car as well?


does sound very volatile though
By AnnihilatorX on 4/4/2008 3:14:53 PM , Rating: 3
It does sound as if you put those saturated with hydrogen with a naked flame, they would explode.

I hope the rate of gas release even at high temperature is quite slow.




By dice1111 on 4/4/2008 3:46:39 PM , Rating: 4
Don't blame them. I explode when I see my hot flame naked as well!


Whats a "basketball field"?
By steelincable on 4/4/2008 2:56:20 PM , Rating: 3
Do they mean basketball court?




RE: Whats a "basketball field"?
By Slash3 on 4/5/2008 2:31:16 AM , Rating: 2
Just imagine the size racquet you'd need for that!

;)


tennis courts?
By neo64 on 4/5/2008 7:46:19 AM , Rating: 2
has anybody paused and reread this line

quote:
Just one gram of the substance has as much surface area as a tennis court, due to its unique design.


again and again?




RE: tennis courts?
By Spookster on 4/6/2008 11:33:42 AM , Rating: 2
Maybe they meant after smoking the crack pipe it seems like the size of a tennis court?


hydrogen storage
By hybuster on 4/11/2008 9:53:39 PM , Rating: 2
The end game is suppose to be hydrogen at the pump. While storage is an issue, if the water released in the exhaust were resplit into hydrogen, no hydrogen stations would be needed and no buckyballs either. When some nation such as Israel has all of their cars running by on board electrolysis into hydrogen, what do we do then. Still chase buckyballs?




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