Chemical process to extract hydrogen - finally a viable alternative to gasoline?

Here’s the original article.
Synopsis: scientists have developed an aluminum-gallium alloy that, when added to water, splits it into hydrogen and oxygen. Right now, they’re working on a way to make the alloy in powder form, which will be easily portable and thus eliminate the need to store or transport hydrogen in large quantities.

The hydrogen can be used to fuel your basic internal combustion engine. According to the article, the only change necessary would be replacing the gas fuel injector with a hydrogen one. (Disclaimer: I know nothing about cars; this may be tantamount to replacing the engine for all I know.)

Once produced in sufficient quantities, the cost of fueling with this method would be comparable to gasoline, with far fewer environmental concerns and (presumably) more stability:

Furthermore, the residue left after use can be recycled back into the necessary alloy, thus providing a far more sustainable fuel source.

So… what’s the catch? There’s gotta be something I’m missing here, but I’m not a chemist or engineer. Any potential big problems, and even then is this still a better option than what we’ve got?

I believe you can use that aluminum directly as one side of a primary battery, and recycle the spent anode into new aluminum more efficiently then using Al to make H2

Where do you get the aluminum?

The hydrogen is produced when aluminum reacts with water to produce aluminum oxide and hydrogen. You then burn the hydrogen to power your car.

The trouble is that aluminum metal isn’t just lying around, you have to create it–by splitting aluminum oxide ore into aluminum metal and oxygen. And that takes energy. And of course, the energy you get from burning hydrogen produced this way will be a lot less than the energy it took to purify the metallic aluminum in the first place.

So this isn’t a source of energy, rather the metallic aluminum is stored energy that came from some other source. Generally aluminum smelters require gigantic amounts of electricity, and can produce some nasty by-products. So to produce the electricity in the first place you’ve got to build nuclear, hydro, or coal power plants. Hydro is out, since we’re pretty much maxed out on potential hydro power in the US. So that means burning coal to produce hydrogen, or nuclear to produce hydrogen. And of course, electricity can split water into hydrogen and oxygen directly. I suppose the advantage of this method is that metallic aluminum is easier and safer to transport than gaseous hydrogen, but that’s about it.

Isn’t gallium rare and expensive? Where do they get it from? Is it difficult to extract?

I remember seeing a picture of gallium in my high-school chemistry book: a lump of the stuff melting in someone’s hand. Gallium has a melting point of 29.5C (a pleasant summer day, and quite a bit less than body temperature (37C)).

The catch is that you have to use an enormous amount of electricity to extract elemental aluminum from its alloy. That electricity is by and large generated by burning fossil fuels.

The second catch is that when you’re out of fuel, not only do you have to put new fuel in, you have to take out the spent fuel and transport it back to a recycling center.

Bingo. You can never, and I mean NEVER, get more energy out than you put in. Never. It’s the second law of thermodynamics. Sure, you don’t directly use energy to get the hydrogen, so it seems like a gain, but when you take in the energy needed to extract, make, and transport the aluminum alloy, then you’re clearly at a loss. That’s also why I am skeptical of biofuels and ethanol engines. Hopw did you convert that corn and waste oil into fuel? I’m guessing you didn’t use compleltly renewable energy, did you?

Basically, until we get to the point where the majority of our electricity usage is from hydro, wind, solar, tidal, etc…, (or at least nuclear) then we are always going to be having a net loss of energy from fossil fuels.

Think of it as dehydrated gasoline that’s really safe to transport, rather than as a primary energy source.

If you need to run an engine or produce electricity in some remote area, you either need to bring in gasoline/diesel fuel, which is bulky and inflammable, or you bring in gaseous hydrogen to power fuel cells, which is also bulky and inflammable. If you’ve got a good supply of water in your remote spot, bring in the aluminum-gallium stuff which is comparatively inert, as far as shipping is concerned, and make hydrogen on the spot.

So you have a system where Al/Ga is slowly introduced to water to produce hydrogen. The hydrogen is “burned” to produce water which could be recycled back into the system or expelled. If it is expelled, then you need to refuel both the water and the Al/Ga alloy, but that probably isn’t difficult. Some type of cartridge could be purchased for refueling the Al/Ga. A filter assembly could be designed to be exchanged for a clean filter at refueling, ensuring that no Al/Ga is wasted. The cartridge and the filter could even be designed into the same thing so that there is no accidentally not exchanging the filter resulting in dangerous pressures. Another advantage of this cartridge design, is that you don’t need to restructure gas stations to supply them. They could simply be stored on the shelf.

As has been pointed out, even if the Al/Ga is recycled you have to rereduce the Al[sup]+3[/sup] to Al[sup]0[/sup] which is a very high energy process. On the otherhand, as long as the power plant associated with this process is nuclear or hydroelectric no greenouse gases are emited. I don’t know anything about the reduction of Ga, but it probably is less complicated than Al.

So how stable is this Al/Ga alloy? Will it burst into flame if the container is ruptured in an accident? (On review of the article I see this is answered as “no”.)

This is similar to the amine borane designes I have seen lectures on. Rather than reacting with water, they release hydrogen upon heating. The minus side to that is that a vehicle fire could be disasterous.

In all truth aluminum by itself will produce hydrogen on contact with water, but it instantly creates a protective coating of aluminum oxide that prevents oxidation any further. (Once again, I see the article addresed this.) I wonder if the Al/Ga alloy has similar troubles and that is why they are looking at a powder. I’m suprised nobody has tried this in the past, it seems rather obvious in hindsight.

I guess another thing to consider is the weight/volume to energy ratio. I think aluminum is pretty big and heavy as hydrogen storage strategies go, but I’ll leave the calculations for someone else to do. And unlike with fuel, you won’t lose the weight as you use the energy up. That is one advantage of amine boranes. They have high hydrogen to weight ratios.

That’s a pretty big advantage, as I see it. It’s the only system I’ve seen so far that allows us to eliminate the use of oil without having to invest in some incredibly huge infrastructure to support it.

Nobody is saying that this Al-Ga-H2O system is an energy source, but if you locate your aluminum recycling plant near a nuclear power plant to obtain the cheap electricity, you are essentially running all your cars on nuclear power - cheap, safe, low pollution, no greenhouse gases. Sounds good to me.

Biofuels are a different kettle of fish - unlike the process being discussed in this thread, the energy in the resulting fuel comes not from the fuel spent harvesting and processing it, but from the net energy input from the sun while the crop was growing.
It’s is theoretically possible for biofuels to yield more energy than it takes to grow/harvest/process them - I don’t know if it’s practically possible right now though.

Aside from the valid issues regarding reducing the aluminum-gallium alloy to a usable form, the notion that you can just pump hydrogen through your gasoline engine is laughably absurd. Gaseous hydrogen is a fairly corrosive gas; at a minimum you’d need to replace fuel lines other non-CRES components. You might have problems with damage to valves and valve seats, and I suspect that any aluminum engine components that see tensile stresses may have problems with stress corrosion cracking. You’ll likely need to replace the crankshaft and cam/valve timing system and reprogram the engine controller to deal with the thermodynamic differences between using hydrogen and gasoline. This is not the simple swapout that the article protrays it to be.

I think the fundamental less to be learned here, however, is that you should never trust automotive engineering advice from pirates. Aaarrrggg!