Silicon Nanoparticles Could Lead To On-Demand Hydrogen Generation

cylonlover writes "Researchers at the University of Buffalo have created spherical silicon nanoparticles they claim could lead to hydrogen generation on demand becoming a 'just add water' affair. When the particles are combined with water, they rapidly form hydrogen and silicic acid, a nontoxic byproduct, in a reaction that requires no light, heat or electricity. In experiments, the hydrogen produced was shown to be relatively pure by successfully being used to power a small fan via a small fuel cell."

Comments

Honest, Officer

[mbstone]

I wasn't having an illegal campfire on the beach. It was the sand reacting with the seawater.

Re:Honest, Officer

[slashmydots]

Having a fire on the beach and having the beach on fire are two completely different things

Re:Honest, Officer

[richtopia]

Keep in mind that hydrogen burns clear, so it will be pretty hard for the officer to discover the fire

Re:Honest, Officer

[tilante]

Flames of pure hydrogen are very hard to see - however, when there are impurities present and also burning, the flame can be very easy to see. See, for example, photos of the Hindenburg burning. Using sea water, the flame would likely be very visible. See, for example, this video showing sea water being burned using a different process for extracting hydrogen from it: http://www.youtube.com/watch?v=e8utkoK2DhA

Re:Honest, Officer

[Jeremiah Cornelius]

This reminds me of yesterday's article - cooling with lasers.

Myself, I once started a forest fire, being careless with an ice cube.

The key question becomes

[Stirling Newberry]

How much energy to create the silicon nanoparticles.

Re:The key question becomes

[jcr]

If it's less than the energy used to make conventional, disposable batteries of equivalent power, it's a win. Even if it's more costly than that in energy terms, it could still be a win from a weight to power ratio standpoint.

-jcr

Re:The key question becomes

[R_Ramjet]

Significant. From the article: "Though it takes significant energy and resources to produce the super-small silicon balls, the particles could help power portable devices in situations where water is available and portability is more important than low cost."

Re:The key question becomes

[snarkh]

Even if it is neither of those it can still be a win if it is non-toxic or easy to dispose of.

Re:The key question becomes

[SJHillman]

I'm hoping this doesn't turn into another "butbutbut but it still takes more energy to make than it gives back!" argument. The key here is making the stored energy portable. Gasoline takes a lot more energy to drill, transport and refine than it gives back, but the end product is very portable so the premium is worth it compared to stuff like coal or natural gas that (presumably, I don't really know) takes less effort to get to the end product. However, coal is pretty impractical for portable applications like cars, lawn mowers or snowmobiles.

Water, on the other hand, has every advantage of gas (liquid can be pumped, etc) with additional advantages such as being much more renewable, much greater availability, much easier to get to and not being explosive if you decide to smoke while filling up. The only problem is that we haven't found a way to convert water into hydrogen fuel (which cannot be as easily stored or transported as water) at the point of use - either the pump or, better yet, whatever needs the fuel. If silicon nanoparticles can do that and you only need to swap in a new silicon nanoparticle cartridge every few thousand miles then it's well worth the extra energy to create them in the first place.

Re:The key question becomes

[Stirling Newberry]

Both this question and the next one roll into what is called the "Life Cycle Analysis" the net output per unit input.

Remember, there is energy extraction, and energy packaging. Petroleum is a huge win, because it is both - refining is relatively cheap, and it packages the result. This is not energy extraction - there is a large input, but it makes a convenient fuel cell package that gets around the problem of storing hydrogen. Since hydrogen is very chemically reactive, it's a big problem in having a hydrogen based energy chain.

The input cost is essential, especially the theoretical efficiency, against other forms of energy storage. This would include how stable the nano-particles are, because water is ubiquitous.

However it could be great for renewables, because the onsite wind farm or what have you, could be used to generate the silnaparts and this stores them. It could also be good for nuclear power, which runs continuously, and thus reduce the need for peak capacity, which is heavily carbon dominated. Even if not very efficient it could significantly reduce carbon footprint, because there would be no concern about the major problems of current bulk energy storage: gravity is environmentally destructive, and batteries have rather low cycle limits.

Re:The key question becomes

[Stirling Newberry]

Theoretical efficiency could be a great deal lower. We are about as good at producing nano anything as Assyrians were at producing steel.

Re:The key question becomes

[Stirling Newberry]

Actually the LCA of petroleum is excellent, that's one of the reasons it took over the world.

It just has unfortunate side effects: it is killing us, and killing our ecosystem, which we are rather dependent on, there being no other garden worlds.

Re:The key question becomes

[Culture20]

Then the question is "how much energy does it take to crack the oxygen back out from the acid?" Start burning that hydrogen everywhere for decades and we'll have a little less oxygen in the atmosphere. Ordinary water cracking leaves the proper amount of H and O for future reacting.

Re:The key question becomes

[DeathToBill]

Um, no. It typically takes around 4MJ/L (just over 1kWhr/L) to refine petrol, while the energy content is 35MJ/L. Drilling and transport add a little to that, but it's negligible compared to refining it. If it wasn't so, using it would have a net negative impact on our energy supply and no-one would use it.

Re:The key question becomes

[ciggieposeur]

Indeed. I work for one of the major "silicon crushers". Converting sand to metallurgical grade silicon (97%+) takes an arc furnace, lots of electrical power required. Then comes grinding and classifying it and most processes deliberately spray the dust with water to put an oxide layer on the particles to prevent a dust explosion.

Re:The key question becomes

[VortexCortex]

If your pathetic genome had better redundancy and error correction you wouldn't care about the radiation.

Oh wook at da poor wittle hue-mans, can't come out an pway in the milky way because them scawed for cosmic rays. Have fun being grounded dork!

Re:The key question becomes

[jcr]

I don't think you have a grasp of the scale of the earth's atmosphere. This might be an issue for people aboard a space station, but on earth it's insignificant.

-jcr

Re:The key question becomes

[dave420]

Like, say, the amount of CO2? Honest question.

Re:The key question becomes

[rot26]

It's a feature, not a bug.

Re:The key question becomes

[SJHillman]

Gas is stored underground at gas stations. Store water underground and it's pretty easy to maintain it at a temperature above freezing... even in climates much colder than Minnesota.

It's also not too difficult to keep it as a liquid using other methods ranging from passive to active.

Re:The key question becomes

[Anonymous Coward]

No need to, the oxygen wasn't in the atmosphere, it was bound to the hydrogen in the water molecules. Water is burned hydrogen, so this oxygen was already "lost".

Re:The key question becomes

[mapsjanhere]

This is strictly for military applications. The US forces in Afghanistan use 28 gallons of fuel to deliver one gallon of fuel to an outpost where a 3 gal/h generator charges an Ipod (don't laugh, that's from an US Army presentation). So, if I can charge my devices of a fuel cell fed by something like this silicon hydrogen generator I might save money not because it's energy efficient in production but energy efficient at the point of use. The reason they use silicon is that it gives you 1 gram of hydrogen per 8 grams of silicon. You could use other, cheaper, metals, but the weight ratio isn't as favorable (iron would require something like 20 to 1). As 1 kg of hydrogen gives you 127 MJ of energy, 1 kg of silicone powder gives you about 15 MJ. Compare that to a battery that gives you less than one MJ/kg, and you see the attractiveness if weight is at a premium.

Re:The key question becomes

[daem0n1x]

You're right, because internal combustion engines don't spend oxygen!

Re:The key question becomes

[Culture20]

No need to, the oxygen wasn't in the atmosphere, it was bound to the hydrogen in the water molecules. Water is burned hydrogen, so this oxygen was already "lost".

Except this method doesn't release the oxygen. The oxygen gets bound into the acid. So when new water is created from the burned hydrogen, it comes from the atmosphere (or some oxidizing agent). With a net "loss" of oxygen to the acid.

Re:The key question becomes

[rgbatduke]

Where does silicon come from? Silicon dioxide, a.k.a. "sand". How tightly is it bound? Very, very, very tightly. Indeed, a whopping 910.86 kJ/mole. So it requires at LEAST this much energy to turn sand into silicon and oxygen, except that one cannot electrolyze or reduce it until it is molten, so add to this enough energy to melt sand, after raising its temperature to some 1500 C. Then, one has to engineer "nanoparticles" out of the purified silicon metal. At a guess -- only a guess, of course -- this involves heating the silicon to the vaporization point and either vapor depositing it on a suitable substrate and scraping off the nanoparticles or spraying silicon vapor into a suitable medium that causes it to condense out small particles and then filtering or otherwise separating out the 'nano' particles from those that are merely small. Sounds like more energy to me.

At the end of the day, you can get at most the 250 or so kJ/mole back from the hydrogen gas produced after the silicon nanoparticles steal the hydrogen back from water. I think it would be an absolute miracle if it this is as much as 10% of the energy invested in making the nanoparticles, and the energy costs are probably at most half of the total manufacturing costs. Down to 5%. Multiply by roughly 50% again (efficiency of fuel cell).

This "Fermi estimate" of the probable economic efficiency is on the order of 2.5%, then, compared to the cost of just buying electricity or any other form of concentrated energy. Even if I'm too aggressive in my pessimism, 10% is a pretty safe upper bound. I'm not seeing this as a game changer. Gasoline or other hydrocarbons are still the gold standard for readily available energy density at ballpark 35 MJ/liter, and don't require investing 20 times the energy eventually recovered in their preparation.

rgb

Re:The key question becomes

[ElectricTurtle]

Why aren't you the Secretary of the Dept. of Energy? I can't understand how a Nobel laureate physicist is running things and seems to be in complete denial about the practical aspects of energy policy. He seems to think we can power the world on puppies and raibows, and it will only cost a billion times more, but everything will work out in the end in magical fantasy land.

Re:The key question becomes

[ElectricTurtle]

I guess we'll know if he comes back... in greater numbers.

Re:The key question becomes

[Electricity Likes Me]

No one makes nanoparticles in large quantity by vapor deposition. You react the silicon to a suitable precursor and then reduce it gently. It's a very high yielding reaction. Silicon tetrachloride would be one example of a precursor you could use (I think there's a few others - there's a guy in my lab who makes a lot of silicon quantum dots).

The big question is how easy it is to go from silicic acid back to nanoparticles - if it can be done electrochemically and relatively efficiently then what's been discovered is a very efficient catalytic process for cracking hydrogen from water.

Re:The key question becomes

[jcochran]

I don't believe you've taken into consideration the oxygen released from converting Silicon Dioxide into Silicon and Oxygen. Looking up Silicic acid, it's a generic term for a family of related acids. Looking at the 4 simplest ones, I get the following equations.

Si + 3 H2O => H2SiO3 + 2 H2
Si + 4 H2O => H4SiO4 + 2 H2
2 Si + 5 H2O => H2Si2O5 + 4 H2
2 Si + 7 H2O => H6Si2O7 + 4 H2

For all of the above equations, each Silicon atom will result in the generation of 2 hydrogen molecules (4 atoms). Which requires 2 Oxygen atoms to convert into 2 molecules of water when burned. However, to create each Silicon atom, one had to break down a Silicon Dioxide molecule .... Which in return released the 2 Oxygen atoms needed to burn the resulting Hydrogen. And just in case you now attempt to claim that it's consuming water. If you dry out the various forms of Silicic acids, you'll find out that they disassociate into various numbers of water molecules and Silicon Dioxide.

It all balances out. All we have is a system in which we can spend energy converting Silicon Dioxide into Silicon and Oxygen. And then use the resulting Silicon to react with water to get dissolved Silicon Dioxide and Hydrogen. And finally, react the resulting Hydrogen with the Oxygen released earlier to get back water.
 

Re:The key question becomes

[rgbatduke]

Because Obama hasn't given me a call yet to make me the offer, I suppose. I'm not sure I accept it if he did -- it has to be a thankless job these days and I'm enough of a climate skeptic to think that energy resources need to have net positive present cost-benefit before implementing them on a broad scale. Until then research and even prototyping is lovely and worthwhile, but no large scale implementation at a loss until it results in something at least cost-competitive with existing fully developed resources.

rgb

Gimme a match, quick!

[Impy the Impiuos Imp]

Silicon Nanoparticles Could Lead To On-Demand Hydrogen Generation

That's some serious R&D by the whoopie cushion industry.

Why "silicon nanoparticles"? Just add water ...

[Ihlosi]

... to sodium. Instant, on-demand hydrogen!

10nm particles...

[BLKMGK]

What's the health impact of these getting into the ecosystem? Pass right thru a human? Cause serious disease? What happens when it hits the water IN a human? If this becomes in any way widespread these are going to be issues.

What's left after the reaction? Must the water be pure or can we produce power from dirty water and do what with what's left? Could this be used to clean dirty water by simply using the water for power? Is oxygen also produced from this - I'd think so right since water is H2O. Are the particles completely consumed in the reaction? No reuse? How much water is used in the manufacturing process to create these particles? What are the waste byproducts for the process of creating these particles?

Still no free lunch

[jamesl]

From TFA ...
Though it takes significant energy and resources to produce the super-small silicon balls, the particles could help power portable devices in situations where water is available and portability is more important than low cost. Military operations and camping trips are two examples of such scenarios.

Great

[pr0nbot]

How long have we got till peak silicon? I'm going to start stockpiling sand for the forthcoming commodities bubble.

Re:Great

[Specter]

Just try to keep your cat out of it, alright?

It's still about net energy

[gestalt_n_pepper]

How much energy does it take to make the stuff, transport it, dispose of it, and so on? It may prove to be an adequate energy carrier if it's cheap enough AND we have enough cheap electricity to make use of it, which might happen if we actually get thorium-based nuclear power AND we can solve the engineering problems involving the use of hydrogen in any metallic machines.

Not a bad technology if it's more energy dense by volume and cheaper than current batteries though.

Re:Bad trade

[higuita]

you don't understand that H2 is very hard to contain, its the smallest of the gases and if it escapes, together with Oxygen produces a very explosive/inflammable mixture.

you need very well constructed (and heavy) containers and very good transfer methods (fool proof).
Also, hydrogen is also corrosive and suffer from migration on metals and other crystalline structures (check wikipedia for more info.)

Compared with the propane gas, its a lot harder to work with and, specially, long term maintenance.

Water, you just need some "bucket" or simple container and that's it, no safety problems (other of people trying to drink it maybe!).
Rust is only a problem with some materials and have currently many easy solutions (other material, coatings, alloys). Unless you are using sea water, its not different from your water supply at home. Even it there is a leak, there is usually no big problem.