MIT Researchers Make Hydrogen Fuel from Aluminum and Water | Hacker News Reader

MIT Researchers Make Hydrogen Fuel from Aluminum and Water

interestingengineering.com

40 pointsmardiyah39 comments

I love that this project investigated some novel surface chemistry. I hate that the article ignores that the aluminum is made using a bunch of electricity.

Just use that electricity to make hydrogen in the first place, hydrolysis is approximately as efficient as aluminum smelting already (and both are over 90%)...

> Using aluminum as our source, we can ‘store’ hydrogen at a density that’s 10 times greater than if we just store it as a compressed gas.

The point is that it is beneficial to store the energy as Aluminium instead of hydrogen gas.

Hydrogen production via electrolysis isn’t over 90% in real systems. It’s more on the order of 70% for real world systems. Some small scale research systems can hit 90% or more for various solid oxide electrodes, but they’re fragile and generally not commercially available yet.

See https://www.sciencedirect.com/science/article/pii/S258929911... as an example overview.

Are you thinking of aluminum recycling, which is much easier than aluminum smelting, which is not an incredibly efficient process? I think recycling aluminum requires 5% of the energy that smelting it requires.

It is possible, I didn't look up numbers. Still, it's hard to imagine inserting a step being a practical solution.

I expect a reasonable high density low pressure hydrogen storage solution to happen sooner at any scale, a solid fuel isn't particularly practical either except in a one-use battery.

That’s a misunderstanding. Aluminium smelting is the process of extracting pure Aluminium from its oxide. https://en.wikipedia.org/wiki/Aluminium_smelting

Recycling generally avoids smelting aluminum because Aluminum in say cans only has an atomic scale coating of Aluminum oxide around pure Aluminium.

Actually, that works in favour of this method here, provided certain conditions are met.

Aluminium takes a big juicy bunch of electricity. Its very energy intensive. But, if we can extract a good portion of that aluminium energy as hydrogen gas, then aluminium acts as a highly energy dense battery.

It can then be effectively used for grid scale energy storage.

I've been doing something similar since I was, like, 10? Put some aluminium in water, add lye, and you got hydrogen. For me it worked because it was faster than electrolysis, enough to fill balloons with. [inb4 yes, my childhood was weird and I got access to lye.]

As another user mentioned however this is more expensive than making hydrogen the "old" way. You're better off recycling the aluminium.

One of my childhood neighbors had an in-ground pool which gave him access to all sorts of pool cleaning chemicals... many an "hcl bomb" were made from 2-liter bottles and aluminum foil scraps.

Yeah I was going to say, when I was a preteen, would mix lye (in principle, sustainably produced via leaching wood ash) with aluminum (not sustainably produced, but readily available), fill up garbage bags with H2 and torch them for lols. A bit scary when the pot got hot enough to boil. Generally stopped blowing things up after sex, drugs, appreciation for injury all started to seem more important

Back in grad school we would put lye, water and aluminum foil in an empty wine bottle, tie a (unused) condom around the neck of the bottle, wait for it to inflate and then light it up with a match tied to a very long stick.

Lye is fairly common. In my childhood you could even buy, as a child, things like potassium nitrate at the drug store.

> yes, my childhood was weird and I got access to lye.

I used to make gunpowder. Sulphur and potassium nitrate at the local pharmacy and charcoal from the BBQ. I wasn't very successful because it all has to be ground really fine without killing yourself. I just lit it never made anything with it more for the science than anything.

The Radioactive Boy Scout was ten years later but if I had been aware of him and of Americium (I probably was) I bet I would have tried that too. I was a nerdy kid on my own but a 75% range (C) student in school.

Weird is good but it seems to be frowned upon these days. Too often it's seen as dangerous to even just ask about certain things.

Hrhrhr. I did pipe-bombs with it with which I've torn down brick walls of abandoned buildings which where already rotten. Water bombs also, with electrical ignition via very thin wires and flashbulbs. I don't get the 'without killing yourself' though. Black powder isn't like the potassium chlorate you have when messing around with fertilizer. You can grind every constituent of it all day like you want. And then mix the grinds together. Maybe avoid static electricity. But that's what cotton clothing is for, isn't it?

Lye, aka the industrial commodity Caustic Soda.

I advise people to stop young, by the time I grew up it was shiploads.

Nobody's fault but mine.

Aluminum (metal) is way more expensive than hydrogen. This is such a waste. Is it prohibitively difficult to recycle this scrap instead?

And if you go with this idea, what do you do with the spent aluminum hydroxide? That's toxic waste,

https://en.wikipedia.org/wiki/Red_mud

I think you've got it wrong. The red mud is not aluminum, it's what's left over from mining aluminum. Aluminum hydroxide is used in vaccines, antacids, and as a precursor to other Aluminum compounds. It can also be converted to alumina under heat, so it should be reusable as a portable hydrogen generator.

You pour the waste into a crater because you're using this technique to create fuel and oxygen from Lunar regolith.

Disclaimer: never took chemistry

but wouldnt it be https://en.wikipedia.org/wiki/Tin(II)_hydroxide ? since aluminum foil is not aluminum?

Reverse that. What is called tin foil is actually always aluminum. Once upon a time, though…

As it is apparently essentially a purified bauxite, I imagine it would be a desirable raw material for an aluminum smelter. Consuming it in this manner would create a closed cycle for generating hydrogen from electricity (as aluminum smelting is an electrolytic process) - electrolysis of water by proxy, if you will.

https://www.usgs.gov/centers/nmic/bauxite-and-alumina-statis...

One downside is that currently, graphite anodes are used, with which the oxygen of the hydroxide anion reacts, creating CO2 in an amount commensurate with the amount of of hydrogen produced - so this process would be far from carbon-neutral, though presumably this CO2 could be relatively easily captured in a pure form (disposing of it is another matter.)

Here's some research into reducing the CO2 production (by 50%) as well as being more efficient, but it is still in development with some as-yet unsolved problems:

https://news.osu.edu/electrode-to-lower-cost-of-aluminum-sme...

You reheat it and deoxidize it. No waste.

Aluminum hydroxide is not toxic waster. You linked to a wikipedia article that has nothing whatsoever to do with aluminum hydroxide. Here's the article on aluminum hydroxide [1]

[1] https://en.wikipedia.org/wiki/Aluminium_hydroxide

The chemistry behind that is simple and well known for some time. The novel idea is that Al can be used as a storage for H which is much denser than you could ever achive with compressing H. In the end a car would then be fueled by an Al rod and water. The whole transportation nightmare of H2 (liquidification, cooling, etc) would be gone. Al is made by electrolysis as is H2. So it is a staged process, where first the Al is made and later transformed to H2 by an exothermic reaction which generates additional heat which can be used for heating or cooling (via adsorption coolers).

> Additionally, even the generation of hydrogen results in the release of greenhouse gases, which quite beats the purpose of using hydrogen in the first place.

Why does every article about hydrogen keep saying this? Running electricity through fresh water generates hydrogen and oxygen. The electricity can come from the nuclear power plant, a solar array, etc...

What am I missing since I first saw hydrogen and oxygen created in high school chemistry?

There was a recent study about generating hydrogen using power from natural gas and capturing the carbon dioxide from it. It found that methane leaks almost certainly made it too dirty to consider as a green energy source. https://arstechnica.com/science/2021/08/blue-hydrogen-pushed... I agree the article left out this important context.

That's just an attempt to make fossil fuels produce green hydrogen. A thing often attempted by the fossil fuel industry to stay relevant.

There are other ways to make hydrogen from water.

The problem is that it is cheaper to produce hydrogen using fossil fuels, instead of using clean energy + eletrolysis.

https://en.wikipedia.org/wiki/Hydrogen_production

> As of 2020, the majority of hydrogen (∼95%) is produced from fossil fuels by steam reforming of natural gas, partial oxidation of methane, and coal gasification.

The so-called "blue hydrogen" is made from natural gas.

... painted the scrap aluminum with a eutectic mixture of gallium and indium

There may be a problem with the economics of this approach.

Fortunately, "the mixture does not react with aluminum and can be recovered at the end of the process and used again."

With how much difficulty?

I doubt this has a practical application (better to just recycle scrap aluminum), but it’s still cool just from a “you can do that” perspective.

So would it be possible to make a mini hydrogen power plant from a rain water cistern and scrap aluminum?

Right? It's like the perfect post-apocalyptic semi-portable power solution.

Al is so easy to melt and recycle though, post-apocalypse the value of the metal is likely higher than fuel

I am not sure fuel won't be coming in magically and everywhere besides the middle East or permafrost all easily accessible fossil fuels have been already exploited.

Yes if you have a way of using generated hydrogen effectively. No idea how easy is to regulate the speed of reaction.

It might be preferable to make aluminium-air battery instead. https://www.youtube.com/watch?v=1ExuhMrnQSw

Looks something pretty short distance from lab to fab ?

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