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Ethylene for Hydrogen Storage

8 December 2006

Ethylene
Attaching titanium atoms (blue) to the ends of an ethylene molecule (yellow-green) will result in a capsule-shaped complex that absorbs 10 hydrogen molecules (red). Click to enlarge.

Results of modeling studies by the National Institute of Standards and Technology (NIST) and Turkey’s Bilkent University indicate that attaching titanium atoms to the ends of an ethylene molecule will result in a capsule-shaped complex that absorbs 10 hydrogen molecules. The results open a new avenue in the pursuit of materials that will enable efficient solid-state storage of hydrogen.

Ethylene is the inexpensive building block of the most common plastic.

The team’s calculations show that attaching titanium atoms at opposite ends of an ethylene molecule (four hydrogen atoms bound to a pair of carbon atoms) will result in a very attractive “two for” deal. The addition of the two metal atoms results in a net gain of up to 10 hydrogen molecules that can absorb onto the ethylene-titanium complex, for a total of 20 hydrogen atoms. As important, the engineered material is predicted to release the hydrogen with only a modest amount of heating.

The absorbed hydrogen molecules account for about 14% of the weight of the titanium-ethylene complex. That’s about double the Department of Energy’s minimum target of 6.5% for economically practical storage of hydrogen in a solid state material. Although significant challenges stand in the way, solid state storage is preferred to storing hydrogen as a liquid or compressed gas, both of which require large-volume tanks.

The success of future hydrogen and fuel-cell technologies is critically dependent upon the discovery of new materials that can store large amounts of hydrogen at ambient conditions.

—Taner Yildirim, theorist at the NIST Center for Neutron Research

Yildirim and collaborators have been searching for routes to develop these needed materials. Their earlier research has pointed to several candidates, including carbon nanotubes coated with titanium atoms. Difficulties in securing bulk amounts of small-diameter nanotubes and other challenges have foiled efforts to create these materials in the laboratory.

The team anticipates that ethylene-based complexes, made with titanium or other so-called transition metals, will prove easier to synthesize and, then, to evaluate for their potential for high-capacity hydrogen storage.

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December 8, 2006 in Hydrogen Storage | Permalink | Comments (16) | TrackBack (0)

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Comments

Do we get 10 or 20 atoms delivered?
If 20 where does the C and Ti end up?
If 10 we aren't talking about 14% anymore.
The resource link is not working at this time, but it
looks like a great way to sop up some grant money.

Another barmy H2 storage idea.

Still misses the point about where the H2 comes from? It is the daftest way of storing energy ever thought of!!

Man, some people will whine about anything.

If this works they'll have solved one of the three main hurdles to H2. (the others being the platinum content of fuel cells and efficient creation of H2 from non-fossil fuels) Even though I favour electricity as a carrier I would still be happy to see this work.

Current PEMFC technology requires ~10x the platinum for the stack that a gasoline ICE car needs for its three-way catalyst. If you now increase the platinum requirement per FCV even further by including it in the hydrogen storage medium, you will pretty quickly run into a hard wall regarding platinum prices/availability.

It's not a significant problem as long as production volumes remain very low. In that case, however, FCVs hardly represent the future of anything other than a few bureaucrats over at CARB.

BEVs are also still expensive but much less so than FCVs. Lithium is a fairly abundant material that poses no significant barrier to expanding market share.

H2 storage technology is essential. Many new technologies are coming up which promise Solar to Hydrogen, or any renewable energy to hydrogen production.
And by the way hydrogen is best kind of fuel possible due to its very high heat of combustion.
Better storage of hydrogen will mean better machines.

If you now increase the platinum requirement per FCV even further by including it in the hydrogen storage medium, you will pretty quickly run into a hard wall regarding platinum prices/availability.

Huh? This proposed molecule doesn't contain platinum.

The link to the article is broken, btw.

I have to wonder if this stuff would be usefull as a way of storing energy from renewables to even out production? Would the amount of Titanium required make it too expensive?

Neil:

Titanium is quite common element in Earth crust, and there are abundant deposits of high concentration titanium ore. 95% of Ti is consumed in form of inexpensive Ti dioxide as whitening pigment in paper, paints, and plastic. Yearly per capita consumption of Ti dioxide is 6 lb for US, 4 lb for Japan, and 0.4 lb for China and India.

Now, the picture changes with Ti metal. It is extremely expensive and energy consuming to purify it into metal form. Since the high price. Hopefully, currently developing Cambridge method will change the picture.

So, use of Ti derivatives are not limited by supply, but rather by price of particular chemical technology.

Ti chemical compound is also used in Altair Nano battery as cathode component.

>Titanium is quite common element in Earth crust ...

I have often wondered about this myself, as TiO nanotubes seem to be a very big deal in newer PV technologies.

According to a geoscience text recommended by my geophysicist wife, Ti occupies 0.86% of the earth's crust by weight. Interestingly enough this is *way* above some other metals which may surprise you, including lead (0.0001%), copper (0.0058%) and tin (0.00015).

What complicates this picture is the fact that an element must be concentrated to a much larger degree to make it economic to extract. For instance, iron is 5.8% of the crust by weight but must be concentrated by a factor of 5 to 10 to be profitably extractable. I would be very interested to know what the current economic extraction concentration factor for Ti is, and how much reserves of that material are available and where they are located.

Andrey is dead right on the fact that titanium metal is obscenely expensive, and AFAIK nearly all of it comes from Russia.

Check out the following links for promising replacements for platinum in many of its industrial uses using nickel-titanium and nickel-cobalt nano particles.

Nickel-Cobalt Alloys

Nickel-Titainium Nano Particles

The first link claims that one could reduce the cost of fuel cell and battery catalysts by 50% with 90% of the performance, and reduce the cost by 90% at 73% of the performance.

If the three main hurdles to H2 are the platinum content of fuel cells, storage of H2, and efficient creation of H2 from non-fossil fuels, we may be down to only one major hurdle soon (economical H2 creation) - at least in the lab anyways (as many of these technologies aren't available to consumers yet, either because of technical or economic/cost issues that do look likely to be overcome).

I think an important way of solving the H2 generation problem in an economical way will be to build nuclear power plants designed for H2 generation, and use the Sabatier method (reacting H2 with C02 at elevated temperatures to create Methane +O2- this process is 96% efficient I believe) to create methane and dump this methane into our regular natural gas pipeline systems. Small home-sized reformers could then turn the CH4 back into H2+C02 for fuel cell use, so this would be a carbon neutral way of generating fossil fuels. Indeed you could just burn it in a CNG car as well or use it for your natural gas heating or stoves.

The economics of unsubsidized nuclear (for either power or CH4 generation) aren't cost competitive yet with current fossil fuel prices. This is a mostly a matter of political will - if legislatures are willing to set up a cap and trade system for green house gases, I think this could easily become an economical system of greenhouse gas neutral fossil fuel production.

Anybody interested in coming up with a cost analysis/comparison of nuclear CH4 production using the Sabatier method? If we had that data we could determine how expensive greenhouse gas credits would have to become before we would see investment in something like this.

Smaller quantites of Ti come from Australia, and oddly, Florida.
_This is still in the preliminary stage. The next step would be to make small quatities of this material, and test it under a variety of conditions. It could be 5 years before we figure out if this is usable, then another 5-10 years until it may see consumers, if ever.

Hmm Sabatier method might actually be CH4 + 2H2O. This means you would be spending the heat energy of the nuclear plant to break H2 off of H20, and only getting half of the H2 to attach to C, the other half going back to water. So using the Sabatier method would be only half as efficient as I though....

Problem of generating the H2 economically?

A recent GCC article citing a Popular Mechanic article has shown that H2 can be produced from waste biomass (gasification) at a price competitive with petroleum. From coal gasification, H2 can be produced even a lot cheaper than petroleum products.

Solar heat can be used to generate H2 via the thermo-chemical process, or solid oxide high-temp electrolysis, or via coverting Zinc-Oxide into zinc metal by heat, then zinc reacted with water with heat to generate H2 and Zinc oxide, all at high efficiency, or the more experimental method of direct spliting of H2O into H2 and O2 via a special solar panel, though still in research stage.

High cost of PEM fuelcells?
How about ICE-HEV at high efficiency? Look at a recent GCC article:
http://www.greencarcongress.com/2006/09/the_arguments_f.html

Problem transporting or storage of H2 ?

Hopefully, this featured technology of high-capacity H2 solid storage will solve this problem. Or, alternatively, one could generate H2 locally within the same city, hence minizing the H2 transportation cost via trucks or dedicated H2 pipeline.
At high vehicular fuel efficiency, compressed H2 tank is somewhat adequate even now.

I like the way the article says "Ethylene is the inexpensive building block of the most common plastic." Never mind the fact that the transition metal reagents cost a gazillion times as much per mole. I don't appreciate such intellectual dishonesty. Nevertheless it is an interesting new system.

If you read the preprints of this article (google for the title), you find that the monomer shown is predicted to be unstable to polymerization. The polymer is predicted to bind about 6% hydrogen by mass. Not bad, but much less than the 14% for the monomer.

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