Scientists Achieve Perfect Efficiency For Water-Splitting Half-Reaction (phys.org) 130
Dthief writes: Splitting water is a two-step process, and in a new study, researchers have performed one of these steps (reduction) with 100% efficiency. The results shatter the previous record of 60% for hydrogen production with visible light, and emphasize that future research should focus on the other step (oxidation) in order to realize practical overall water splitting. The main application of splitting water into its components of oxygen and hydrogen is that the hydrogen can then be used to deliver energy to fuel cells for powering vehicles and electronic devices. The process involves exposing the water to a mass of platinum-tipped nanorods, with visible light driving the reaction.
The 100% efficiency refers to the photon-to-hydrogen conversion efficiency, and it means that virtually all of the photons that reach the photocatalyst generate an electron, and every two electrons produce one H2 molecule. At 100% yield, the half-reaction produces about 100 H2 molecules per second (or one every 10 milliseconds) on each nanorod, and a typical sample contains about 600 trillion nanorods.
Oh well. (Score:5, Funny)
Too bad there aren't any uses for oxygen.
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I'm not sure I'd want to hang out near the exhaust pipe of such an engine. O2 is rather explosive.
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I'm not sure I'd want to hang out near the exhaust pipe of such an engine. O2 is rather explosive.
No... O2 is not explosive. It is an oxidizer. It requires a fuel to burn.
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Like... your nostrils?
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Yes, your nostrils also need a fuel to burn.
But seriously, if you have pure O2 coming out of your nostrils, then something is seriously wrong with your respiratory processes and you should probably get back to Area 51 at your earliest convenience.
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If you lived on Titan, you might see things the other way around.
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Like H2?
Re:Oh well. (Score:5, Interesting)
False.
Pure O2 is the only thing which breaks the fire triangle (fires require oxygen, fuel, and ignition sources)
It's oxygen, so that's one corner of the triangle.
It turns almost anything into a fuel and handling it is incredibly difficult because of this. For example pure O2 pipelines have "fuses" put into them which is basically a section of teflon pipe with high pressure water jets directed at it because the metal pipework itself becomes a fuel in the presence of pure O2. Most things which aren't a fuel in normal air burn spectacularly in the presence of concentrated O2. That's the second corner of the triangle.
Also pure O2 is easily ignited by any particles in the O2 stream. There's a separate specification for construction and cleaning of O2 carrying systems on top of the standard pipe spec because of this, as well as special ordering requirements for any equipment used in O2 services. If that isn't bad enough it can spontaneously combustion due to adiabatic compression by something as simple as a valve moving too quickly. That's the final corner of the triangle.
In industry O2 is handled like an explosive and highly volatile substance. The exception is when it is in stationary containment (i.e. a gas cylinder). In most plants handling pure O2, the pipework has special identification on it to ensure people stay the heck away from it.
Re: Oh well. (Score:1)
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Our hospitals have the same. All the staff get mandatory training on the hazards of pure O2. Though the hazards are considerably lower at the low pressure and flows used in hospitals and small labs. Your callousness doesn't change the dangers associated with it.
Re:Oh well. (Score:4, Informative)
The engine is the oxidation part. It outputs water, not O2.
The process described in the arcticle would happen in an industrial complex of some sort.
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The engine is the oxidation part. It outputs water, not O2.
I don't think so. The reduction half reaction they're talking about is
2 H+ + 2 e- -->H2
It has to be paired with and oxidation half-reaction. In this case:
H2O --> O2 + 4 H+ + 4 e-
The whole reaction provides H2 and O2 that can be used in a completely different reaction to drive fuel cell or heat engine.
Redox (Score:2)
I wonder...
The dissociation reaction H20 -> OH- + H+ occurs spontaneously in pure water. Combine that with their reduction reaction, and you could potentially produce H2 without further inputs, at least until the OH- concentration built up enough to strangle it.
If using a continuous flow of fresh water instead of a fixed reservoir, you could keep the reaction up indefinitely. Though I suppose the H2 concentration would probably remain low enough to stay fully dissolved in the water. And even if you co
Re:Oh well. (Score:5, Interesting)
the cheapest way to store the oxygen so you can use it later is to not store it, releasing it into the atmosphere, and later just use "air" for the reaction. :-)
Not when you consider the total cost. Air is about 78% Nitrogen, which leads to a lot of inefficiency. Most engines will run much more efficiently with straight O2, or even O2 and some other substance such as injected water. Coal burning power plants that do carbon sequestration use air stripped of N2 so they don't have to separate the CO2 from the N2 in the exhaust. Nitrogen in a combustion chamber also leads to a lot of nasty pollutants that are difficult and expensive to remove. If you are producing pure O2, just venting it into the air is a big waste.
Re:Oh well. (Score:5, Funny)
Not that hard just add water and pipe it away as very weak nitric acid which is pretty well how "scrubbers" work.
At a power station where I did some work the new manager decided he wanted nice white smoke coming out of the stack for PR reasons. So somebody played with the settings on the scrubber injecting a lot of water into the exhaust which came out as nice white steam. That night was very still, the water condensed out of the air and the utility had to pay for repainting thousands of cars in the city that had nitric acid damaging the paintwork.
Re:Oh well. (Score:4, Informative)
I do agree, though, that it makes more sense to store the O2 than to vent it. There are plenty of uses for bottles of pure O2.
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Well, if we were producing H2 on a scale to replace gasoline as a portable fuel source, then I'd venture a guess that the amount of O2 produced would be several orders of magnitude greater than produced as a byproduct of liquid nitrogen production.
Re:Oh well. (Score:4, Interesting)
How do you figure that's carbon neutral? You're still converting all that geologically sequestered carbon into CO2.
Just because you're scrubbing it from the exhaust and temporarily storing it somewhere doesn't mean it's not there. So far as I've heard, we've yet to come up with a way to store CO2 in the long term. Pumping it into the ground is only a temporary buffering solution, as it begins to leak out almost immediately. Undersea storage is a bit more effective, but much more expensive, and has a devastating effect on the fragile sea-bottom ecosystem with unknown long-term consequences.
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Re:Oh well. (Score:5, Interesting)
what do they mean with two step? (Score:3)
the article is confusing. googling for water splitting half reaction results mostly just in this article or copies of it itself.
they can pluck the h2 from the O but the O doesn't want to O2? and it just reacts back to water? so they can make H2 from water with 100% efficiency except that they can't?
in their not-just-water(they mention "high ph") solution? I'm not sure this is big enough news to tout all over the world with a trombone as they seem to be doing.
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Nowhere does it state Oxygen is produced in the process.
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Only Jean Michel Jarre can produce Oxygène.
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That may be true, but only The Orb can produce Toxygene.
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Well played, sir. :)
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Re:what do they mean with two step? (Score:5, Informative)
They are not splitting water at all. They are just encouraging individual H atoms (H+ ions, or basically protons) to combine into H2 molecules.
Normally, even pure water has a whole lot of individual H+ ions floating around in it, and the same number of OH- ions. Those H+ don't combine into H2 because that would require extra electrons, which are stuck in the OH- ions. That's why you can create H2 using an electric current which delivers the missing electrons so the H can pair up. (This doesn't work very efficiently in pure water, but a bit of catalyst helps a lot.)
Acidic solutions have more H+ (along with negative ions from the acid, like for example HSO4-), basic solutions have less H+ (and more OH-)
Apparently the researchers are using a basic solution (high pH, lots of OH- and less H+), and then using photons to liberate electrons from the OH- to allow H+ to combine into H2.
This works best in a basic solution because the problem is not so much the number of H+, but rather the number of OH- ions that can be persuaded to give up an electron by nudging them with a photon. In an acidic solution, most of the eligible electrons are stuck in the negative ions from the acid which are much more possessive of their electrons.
The big novelty is apparently that they can get the OH- to give electrons to the H+ and let them combine into H2, rather than combining back into H2O.
Re:what do they mean with two step? (Score:5, Informative)
Apparently the researchers are using a basic solution (high pH, lots of OH- and less H+), and then using photons to liberate electrons from the OH- to allow H+ to combine into H2.
That would leave you with uncharged hydroxyl radicals with an unpaired electron, so I don't think that's what they're doing. They are only talking about the reduction half reaction (2 H+ + 2e- --> H2). There has to be an oxidation half reaction. You're proposing (OH- --> OH + e-), but they're talking about splitting water, ie : 2 H2O --> O2 + 4 H+ + 4e-
I suspect they need the high pH to let the H2 diffuse away.
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Does it scale? (Score:1)
I make that one ten millionth of a mole of H2 per second. Not exactly going to be making industrial quantities via this method, are we?
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Your math is right based on the summary but the article says:
"With a stable system and a turnover frequency of 360,000 moles of hydrogen per hour per mole of catalyst, the potential here is real."
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Yes, but a mole of hydrogen weighs less than a penny, while a mole of nanorods weighs about as much as you or maybe your car or house.
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https://what-if.xkcd.com/4/ [xkcd.com]
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Your math is right based on the summary but the article says:
"With a stable system and a turnover frequency of 360,000 moles of hydrogen per hour per mole of catalyst, the potential here is real."
Yes, but the specific numbers given would indicate 360,000 MOLECULES/hour, which makes it seem much more likely that the article itself misspoke by saying "moles" where it should have said "molecules"
Sanity check: 360,000 moles/hr per mole of catalyst = 100 moles/sec per mole of catalyst = 6x10^25 reactions/sec per molecule of catalyst.
You can't get a reaction time of 1/(6x10^25) sec = 1.7x10^-26 sec for chemical reactions in our current universe (maybe in a Big Bang)
1.7x10^-26 sec is FAR less time
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It's never too early to say that.
"Fuck you, oil companies!"
The article doesn't enable that, or make it any more useful, but it also doesn't make it any less satisfying.
What about energetic yield? (Score:2)
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You, um, need to read the second paragraph of the summary. That 100% DOES refer to quantum efficiency -- they're claiming that essentially every photon that reaches the catalyst frees an atom of hydrogen.
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Activated by photons, you know like a solar cell?
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Got to capture those electrons in useful form - no good liberating an electron and having it resorbed a few nanoseconds later.
Corroding nanorods (Score:3, Insightful)
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When I see platinum nanorods in water, I worry that anything more than absolutely pure water will leave its "more" deposited on the nanorods, rendering them useless in a big big hurry.
The thing is (Score:2)
and a typical sample contains about 600 trillion nanorods.
That sounds like a lot, but Avogadro's number is still way, way bigger than that. How many decades before this produces 1 mole (2g) of hydrogen gas?
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about 3.8 months, unless I dropped a decimal. 6e23 atoms wanted / 6e14 rods means we need to generate 1e9 atoms per rod; at 1e-2 seconds per atom per rod, that's 1e7 seconds or 115ish days.
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Or one could use multiples of "a typical sample".
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You forgot to factor in that the sun is only up for half the day (on average). So only 12 hours a day will have usable light. My math rounds out at 231 days per mole. Factor in real world limitations like the effect of weather and I would estimate somewhere in the neighborhood of a year per mole when it's all said and done. I think they're going to need a whole lot of these things to be actually useful.
Still in all, it's a good advancement in the right direction.
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You forgot to factor in that the sun is only up for half the day (on average). So only 12 hours a day will have usable light.
But then there's cosine error from the light not hitting the surface straight on. (At a solar-farm level it applies even to tracking systems, since you're really interested in the amount of ground surface area involved.)
Then there's things like non-noon light taking a longer path through the admosphere (especially near sunrise and sunset) latitude, weather, season, altitude, near-hor
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about 3.8 months, unless I dropped a decimal. 6e23 atoms wanted / 6e14 rods means we need to generate 1e9 atoms per rod; at 1e-2 seconds per atom per rod, that's 1e7 seconds or 115ish days.
The paper is restricted (paywalled?), but assuming 600 trillion nanostructures, sqrt(600 trillion) is a square about 24 million on a side. The Platinum atomic radius is about 0.13 nanometers, so rods 1 nanometer wide mean that the "typical sample" is 24 million nanometers on a side, or 24 mm on a side.
Assume a typical sample is 1cm (10 mm) on a side, a square meter would be 100cm x 100cm, or 10,000 times more.
Using your figures, 1e7 becomes 1e3 seconds, or about 15 minutes, unless I dropped a decimal or my
Still has the problem of night (Score:2)
This process requires day light to function, therefore it's potential output is limited by the amount of time the sun shines. Not only is there night but also clouds.
I hate solar power, not just because it is so limited but because so many tree hugger types flock to it. The chemistry of this process is very interesting but if used to convert sunlight to hydrogen then I believe this is a waste of time. Solar power is a distraction from energy production schemes that actually work.
Let's take a look at the
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All it needs are photons, I wonder if Co60 decay photons do anything good for them?
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Just ignore that and think manly thoughts about the Apollo program like the rest of us. It's an engineering thing and not a "tree hugger" thing.
Since it's on a tiny scale with potentially a vanishingly thin coating I'd say just about everything else, especially since it's just about as corr
Re:Still has the problem of night (Score:5, Informative)
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Re:Still has the problem of night (Score:5, Informative)
Solar power is a distraction from energy production schemes that actually work.
Solar power is the root of all energy production schemes that actually work. With maybe an exception for nuclear. It's the only energy input into our otherwise closed system. Oil and coal are both sequestered solar power, while wind and hydro are both driven by solar power converted to heat.
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You are forgetting geothermal, which might be partially nuclear in nature, if I'm not mistaken. Come to think of it, solar power is also nuclear at its root (except fusion, not fission). So it's all nuclear all around.
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OK. Geothermal, yes. But the cause of the energy in solar power isn't really relevant since that in itself is outside the Earth's energy system.
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This is not an attack, I'm genuinely interested here:
What do you figure is the break-even point between the car + solar + storage + maintenance vs. ICE car + gas + maintenance? Which component do you think will give out first, and when do you think it will give out? I'm interested because I actually have some solar guys coming to the house Saturday to discuss some panels, and I'm curious how you figured the value of the deal. For me it would start by offsetting grid power, but I would love to be able to
Wait a minute... (Score:2)
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It wouldn't have taken so long if they focused on splitting yo mommas legs instead.
Pow! Chair to the face!
ExxonMobil president here (Score:3)
Thanks for the tip guys!
There is definitely more energy (hydrogen) in the oceans than there is in those silly oil patches. Who needs water anyway?
We might have to make a deal with Nestlé but this should come along well.
https://www.salon.com/2015/04/... [salon.com]
Truly yours,
Rex Wayne Tillerson
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Gee... can't you read? I am switching ExxonMobil into an hydrogen producer and the hydrogen will come from water. I have to make a deal with Nestlé because they already have water patented in some part of the globe. Who is talking about fracking and bottled water? Not me...
Here is Nestlé CEO goal and they have some advance on us, hence the required deal between us:
http://www.naturalnews.com/040... [naturalnews.com]
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I'd say that the AC can read rather well... Your implication in referencing that Salon article (really? Salon?) is that Nestlé is a nefarious corporate entity in California, profiting from a water shortage that it is helping to produce. While that may be technically true in the most pedantic sense -- they sell bottled water, some of which comes from California taps which are being depleted -- it's not true in a practical sense as the AC pointed out. Moreover, Nestlé is acting well within their ri
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Wake the fuck up. I am just a professional humorist testing my puns here on /. before the show.
Thanks for your participation.
-Rex Wayne Tillerson
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There is definitely more energy (hydrogen) in the oceans than there is in those silly oil patches.
No there isn't. There is energy in light and it can be captured by breaking the bond in water.
And it's this energy that you get back by burning hydrogen to water.
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brilliant! At least somebody knows what she/(he) is talking about in here...
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Or you could just run solar and a battery and not bother will all that junk.
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Hydrogen will become very interesting once hydrogen storage containers come down in price due to economy of scale. Anyone with a water hookup and sunlight could run their own hydrogen refueling station.
Many things get interesting with economies of scale, but that's putting the cart before the horse. New technologies have to be viable for public/private investment from the outset.
OMG, here come the scammers (Score:2)
Oh my God... I can hear the "Run your car on water" scammers firing up their computers right now. There's bound to be another wave of crappy scams for sale online which will tout this as the kind of breakthrough that has finally made it practical to boost your mileage by 500% and reduce gas costs by 600%. Just send $49.95 now for the secrets of how this nano-technology can let you split water into hydrogen and run your car for free!
Groan!
Even PT Barnum would roll in his grave!
Peak Water (Score:2)
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Well, with global warming and all, we can start to reverse the ocean's rise with this wonderful new technology.
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Re:Peak Water (Score:4, Interesting)
A hydrogen economy would be useless for exactly that reason. To store hydrogen, you need exotic materials and high-energy cooling systems. Hydrogen leaks through sealed steel; you'd need to use a lot of energy to keep a hydrogen storage unit idle. This is okay when you're making, shipping, burning; but it's not okay when you fill up your gas tank once a month.
If they could combine the hydrogen with CO2 and make O2+C4H, they could use methane to drive fuel cells or internal combustion. You can actually store methane.
The numbers say... (Score:2)
100 H2/s/rod * 600 Trillion rods / sample = 6 * 10^16 H2/s/sample
High number, but small compared to Avogadro's number: Na = 6*10^23
I.e. it takes approximately 10^7 s (~117 days) to produce one mole (~1g) of hydrogen gas (per sample).
If you would construct a factory which produces a ton (a bit modest, but still) on H2 every day, you'd need 10^6 grams per day. That leads to 10^6*117 ~ 10^8 samples.
I wonder that a sample costs... and what the price of a ton H2 is currently on the market. Let me make a wild gue
Comment removed (Score:4, Interesting)
Not necessarily about bulk price (Score:1)
It's not just the sale price, but what you can accomplish when this process is doable on-the-fly and/or portable.
Entropy (Score:4, Insightful)
Entropy just isn't what it used to be.
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It's a hell of a lot bigger now than when I was a kid.
Useless for vehicles, waste of energy (Score:2)
Elon Musk says it best. "Hydrogen is an incredibly dumb” alternative fuel
http://thinkprogress.org/climate/2015/02/12/3621136/tesla-elon-musk-hydrogen-dumb/
Hydrogen Combustion is a better than Electric cars (Score:2)
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Only if you're using air instead of the oxygen you just made when you cracked the water.
decent (Score:2)
Quantum mechalical Splliting (Score:1)
Attach it to long carbon chains (Score:2)
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When are you going to fire this idiot editor, whipslash?
Agitating to get someone fired while sitting in nice, cozy anonymity. Yup, classy behaviour indeed. Asshole.
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Would it be faster if the hydrogen didn't covet its neighbor's wife ?