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Purdue Researchers Refine Aluminum-Gallium Alloy for On-Board Hydrogen Production; May Meet DOE 2010 Target of 6% Hydrogen Mass Density

Aluminum-Gallium (Al-Ga) phase diagram. The “Ga-rich liquid” refers to Prof. Woodall’s 1982 patent. (Below) Click to enlarge.

Researchers at Purdue University have further developed their technology, announced earlier this year, for cost-effective hydrogen production via the splitting of water with an aluminum-gallium alloy.

Aluminum reacts vigorously with water to produce hydrogen, alumina (aluminum oxide, Al2O3) and heat in the reaction:

2Al + 3H2O → 3H2 + Al2O3 + heat

This basic property has lured numerous researchers interested in generating hydrogen from the aluminum-water reaction for modern transportation systems for at least 35 years.

A 1972 paper by I.E. Smith from Cranfield Institute of Technology summarized past efforts and proposed a mechanism for “Hydrogen generation by means of the aluminum/water reaction”.

However, air-exposed aluminum forms a passivating skin of alumina that protects it from further rapid oxidation. A viable aluminum-water hydrogen system must overcome the protective layer to allow the reaction to continue, while still meeting the other constraints for on-board hydrogen storage or generation. A number of efforts over the past decades have explored the potential of developing an amalgamated aluminum surface that can sustain the reaction with water.

The basic approach taken by Purdue professor Jerry Woodall, the inventor of this aluminum-gallium process, is to disrupt the passivating oxide skin with the gallium component of the alloy.

The gallium component is inert, which means it can be recovered and reused.

This is especially important because of the currently much higher cost of gallium compared with aluminum. Because gallium can be recovered, this makes the process economically viable and more attractive for large-scale use. Also, since the gallium can be of low purity, the cost of impure gallium is ultimately expected to be many times lower than the high-purity gallium used in the electronics industry.

The aluminum oxide product of the reaction can be recycled back into aluminum. The recycled aluminum would be less expensive than mining the metal, making the technology more competitive with other forms of energy production, Woodall said.

The Purdue researchers are developing a method to create particles of the alloy that could be placed in a tank to react with water and produce hydrogen on demand. Since the technology was first announced in May, researchers have developed an improved form of the alloy that contains a higher concentration of aluminum.

In recent research, the engineers rapidly cooled the molten alloy to make particles that were 28% aluminum by weight and 72% gallium by weight. The result was a metal stable solid alloy—able to be handled like a solid, rather than a liquid—that also readily reacted with water to form hydrogen, alumina and heat, Woodall said.

Following up on that work, the researchers discovered that slowly cooling the molten alloy produced particles that contain 80% aluminum and 20% gallium.

Particles made with this 80-20 alloy have good stability in dry air and react rapidly with water to form hydrogen. This alloy is under intense investigation, and, in our opinion, it can be developed into a commercially viable material for splitting water.

—Jerry Woodall

Assuming 50% of the water produced as waste is recovered and cycled back into the reaction, the new 80-20 alloy has a hydrogen mass density greater than 6%, which meets the DOE’s 2010 goal.

Recent findings are detailed in the first research paper about the work, which will be presented on 7 Sep during the 2nd Energy Nanotechnology International Conference in Santa Clara, Calif. The paper was written by Woodall, Charles Allen and Jeffrey Ziebarth, both doctoral students in Purdue’s School of Electrical and Computer Engineering.

Aluminum is refined from the raw mineral bauxite, which also contains gallium. Producing aluminum from bauxite results in waste gallium.

The researchers note in the paper that for the technology to be used to operate cars and trucks, a large-scale recycling program would be required to turn the alumina back into aluminum and to recover the gallium.

The Purdue researchers had thought that making the process competitive with conventional energy sources would require that the alumina be recycled back into aluminum using a dedicated infrastructure, such as a nuclear power plant or wind generators. However, the researchers now conclude that recycling the alumina would cost far less than they originally estimated, using standard processing already available.

Since standard industrial technology could be used to recycle our nearly pure alumina back to aluminum at 20 cents per pound, this technology would be competitive with gasoline. Using aluminum, it would cost $70 at wholesale prices to take a 350-mile trip with a mid-size car equipped with a standard internal combustion engine. That compares with $66 for gasoline at $3.30 per gallon. If we used a 50 percent efficient fuel cell, taking the same trip using aluminum would cost $28.

—Jerry Woodall

The Purdue Research Foundation holds title to the primary patent, which has been filed with the US Patent and Trademark Office and is pending. An Indiana startup company, AlGalCo LLC., has received a license for the exclusive right to commercialize the process.

In 1967, while working as a researcher at IBM, Woodall discovered that liquid alloys of aluminum and gallium spontaneously produce hydrogen if mixed with water. The research, which focused on developing new semiconductors for computers and electronics, led to advances in optical-fiber communications and light-emitting diodes, making them practical for everything from DVD players to television remote controls and new types of lighting displays. That work also led to development of advanced transistors for cell phones and components in solar cells powering space modules like those used on the Mars rover, earning Woodall the 2001 National Medal of Technology from President George W. Bush.

Also while at IBM, Woodall and research engineer Jerome Cuomo were issued a US patent in 1982 for a solid state, renewable energy supply. The patent described their discovery that when aluminum is dissolved in liquid gallium just above room temperature, the liquid alloy readily reacts with water to form hydrogen, alumina and heat.

Future research will include work to further perfect the solid alloy and develop systems for the controlled delivery of hydrogen.

The 2nd Energy Nanotechnology International Conference is sponsored by the American Society of Mechanical Engineers and ASME Nanotechnology Institute.




Why not just use the aluminum directly in a metal-air fuel cell? It would be more efficient, metal-air fuel cell achieve efficiencies in the 60s% range, not to mention the wasted energy in converting aluminum into hydrogen.

Adam Galas

I heard Doctor Woodall on Science Friday and on Inside Renewable Energy, when asked why not just use the electricity needed for recyling alumina, he said that his method was more energy dense than batteries.

The thing is, energy density is meaningless once the batteries exist to make a Prius sized EV go 300 miles/charge.

He mentioned that recycling alumina could be done at 50% efficiency, which means that EVs charged straight from the socket are still more efficient.

Also, how does one remove the alumina from your tank? Can you do this at home?

Do you need to redesingn gas stations to extract it?

You could make a removable tank that could be replaced with a fresh one, but then you really need to redesign the car.

Dr. Woodall's research is interesting, but the fact remains that EVs will always be cheaper than Fuel Cells to make, fuel and maintain.

Don't forget that the fuell cell stack still needs platinum for the catalyst, the most expensive metal on earth.

A Nanoposphate battery needs, lithium, iron and phosphate, all of which are in good supply and relativly cheap.

By the time Dr. Woodall's work is ready to be incorporated into a fuel cell car, BEVs will be dominant.

This work is interesting but soon to be irrelevant.


@ Ben:

Excellent point that is often missed in the race to invent processes to bring H2 to the market. Still haven't read about an H2 gen process yet that is net positive unless it uses some form of sun energy, like electrolysis from water and solar cells, etc. And, so far those processes won't come close to meeting the projected marketing demand

One more observation: seems to be lots more support by the feds to fund H2 research than batteries; I wonder why. Is someone stalling battery development? Who would stand to lose the most if there were off-the-shelf Li Ion cells available right now? Big Oil? I don't know the answer, I'm just asking the question!



We can replace seventy per cent of our transportation fuel RIGHT NOW with electricity generation and battery technology already extant. I don't know where that is from, but I do know that I believe it. I also know that there is enough wind in North Dakota to power all of the continental United States.

Biofuel electric hybrids. It's bulletproof simple. Butanol, biodiesel, and Lithium Ion. Hell, NiMH, even.

Big oil is sponsoring hydrogen fuel cells. We get most of our hydrogen from natural gas. Put two and two together, people!

Rafael Seidl

This discovery has exactly zero chance of ever making it into a civilian light duty vehicle. However, there may be military applications, especially small reconnaissance submarines or torpedoes. The fuel and fuel cell can be pressurized such that the exhaust vapor can be released into the ocean.

Even then,
A small bottle of compressed hydrogen is much lighter and contains much more energy than a box of aluminium + a bottle of water. Remember that the smaller the bottle, the smaller becomes the tension on the wall of the bottle. This means that a small hydrogen container is much simpler to make than a big-one.


I wonder if this type of thing would have application in aviation where there are strict weight/volume limitations. An electric motor turning a propeller driven by a fuel cell. If I wasn't still half-asleep, I would run some numbers myself :-).

Adam Galas,

Can you imagine a semi-truck powered on lithium ion batteries? Lithium Ion batteries will do great for cars but they aren't for everything.

Actually, it is the oposite. A car, has (compared with a truck) a relatively high surfase, but a relatively low weight. So you need a lot of energy (and thus batteries) to deliver the power to keep it running. It is easy to gain speed, but it keeps a lot of energy to keep the speed.
A truck is the oposite : you need a lot of energy to accelerate the 20 tons, but it take relatively few energy to keep it goïng. In addition, when braking, most of the energy can be recycled.
Additionally, many trucks need to keep the engine running while unloading. If everthing is elektric, this may spare a lot of fuel, noice, fumes and money.



I think your statement "once the batteries exist to make a Prius sized EV go 300 miles/charge" is the kicker. Having such batteries is not a given. One hopes that they will develop, but you can't count on it. Like fusion was supposed to be a viable power source in twenty-five years, thirty years ago.

As for the Aluminum-->Hydrogen, it may have it's place, but I just don't see it on a large scale.

Adam Galas

tthoms: you are partially correct.

Calcars has found that it a Prius in EV mode can go 5 miles/Kwh.

So 300 miles requires 60 Kwh battery.

Currently, Li+ batteries have energy density of 115 wh/kg, so you would need 522 kg of batteries, 1150 lbs.

Now, an EV prius wouldn't need the engine, which weighs a couple hundred lbs. You can also throw out the transmission and a few other unecessary componenets, but the EV Prius would still weigh slightly more.

However, battery energy capacity has been increasing by 9% annually for a while now, and with nano tech, it should continue to do so, especially with the increased investment in battery tech.

So within 7 years we will have the battery pack down to 600 lbs, including cooling system and control systems.

Add up the weight of the components you replace, (engine, transmission, ect.) and you find the EV Prius weighs the same as the CAl cars version, thus preserving the 5 miles/Kwh numbers and making the EV prius a reality.

Adam Galas,

It seems obvious that by doubling the energy density from 115 Wh/kg to 230 Wh/kg a Prius with 300 miles all-electric range becomes a reality.

Correct me if I'm wrong but Electrovaya already has such a battery. What is stopping its use in a Prius BEV?

Just to make it sound even better, Electrovaya is developing a 330 Wh/Km
battery pack. How far would it drive an improved Prius BEV?


This technology will probably never be used due to the cost of Gallium. In order to store 1kg of hydrogen (a practical hydrogen car will need at least 5kg) 16kg of AlGa alloy would be needed. Gallium would be 20% or 3.3kg. Gallium currently costs approximately $700 per Kg (not too long ago it was selling for $2000kg). So in order to store 1kg of hydrogen, $2333 of gallium would be needed. A tank capable of storing 10kg of hydrogen would weight 160kg (352lbs) and have $23000 of gallium. Currently there is not a lot of demand for Gallium. If this technology were to be implemented on a wide scale the cost of gallium could easily be triple todays cost.


This technology will probably never be used due to the cost of Gallium. In order to store 1kg of hydrogen (a practical hydrogen car will need at least 5kg) 16kg of AlGa alloy would be needed. Gallium would be 20% or 3.3kg. Gallium currently costs approximately $700 per Kg (not too long ago it was selling for $2000kg). So in order to store 1kg of hydrogen, $2333 of gallium would be needed. A tank capable of storing 10kg of hydrogen would weight 160kg (352lbs) and have $23000 of gallium. Currently there is not a lot of demand for Gallium. If this technology were to be implemented on a wide scale the cost of gallium could easily be triple todays cost.


Try driving a hybrid or EV semi-truck up the rocky mountains. Cargo trucks often need high power for long time periods, so a fuel cell and biodiesel are more viable options for them then batteries.

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