Producing hydrogen from water with carbon / charcoal powder

Aug 28, 2013

In the latest advance in efforts to find an inexpensive way to make hydrogen from ordinary water—one of the keys to the much-discussed "hydrogen economy"—scientists are reporting that powder from high-grade charcoal and other forms of carbon can free hydrogen from water illuminated with laser pulses. A report on the discovery appears in ACS' Journal of Physical Chemistry C.

Ikuko Akimoto and colleagues point out that traditional approaches to breaking down water, which consists of hydrogen and oxygen, involve use of expensive catalysts or electric current passed through water. Since economical production of hydrogen from water could foster a transition from coal, oil and other fossil fuels, scientists have been searching for less expensive catalysts. Those materials speed up chemical reactions that otherwise would not work effectively. Based on hints from research decades ago, the scientists decided to check out the ability of carbon powder and charcoal powder, which are inexpensive and readily available, to help split from oxygen in water.

Akimoto's team tested carbon and charcoal powders by adding them to water and beaming a laser in nanosecond pulses at the mixtures. The experiment generated hydrogen at room temperature without the need for costly catalysts or electrodes. Its success provides an alternative, inexpensive method for producing small amounts of hydrogen from water.

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More information: "Hydrogen Generation by Laser Irradiation of Carbon Powder in Water" J. Phys. Chem. C, Just Accepted Manuscript. DOI: 10.1021/jp4012558

Abstract
We report the photochemical activity of carbon powder in the generation of hydrogen from water by laser irradiation, without any electrodes and photocatalysts. The gas was obtained by laser irradiation in the VIS-NIR range and was dependent nonlinearly on the laser power density. From a gas component analysis and a repeated irradiation experiment, it was found that the carbon powder was oxidized and acted as a sacrificial reagent in the photochemical hydrogen generation. In addition, a highly carbonized charcoal, known as Bincho-tan, was found to effectively work for the hydrogen generation.

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User comments : 7

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dschlink
1 / 5 (1) Aug 28, 2013
I fail to understand how a process that requires a nanosecond laser can possibly be cost-effective.
holoman
2.3 / 5 (3) Aug 28, 2013
"Its success provides an alternative, inexpensive method for producing small amounts of hydrogen from water." from article.

Oh jeah I should be able to use the timble full of hydrogen H2 per month to power my IPOD for a half hour.

Come on, get serious, this is just Medicine Man Science, useless to the
world's population.

Very disappointed in Physorg for putting this up.
TheGhostofOtto1923
2 / 5 (4) Aug 28, 2013
I fail to understand how a process that requires a nanosecond laser can possibly be cost-effective.
Here you go.
http://www.onefiv..._xp.html

-Cheap.
Eikka
5 / 5 (4) Aug 28, 2013
it was found that the carbon powder was oxidized and acted as a sacrificial reagent


In other words, they re-invented town gas.

Gasworks used to produce lighting gas by heating a bed of charcoal until it glows and spraying it down with water. The difference here is that the reaction happens nominally at room temperature because only a tiny portion of the mixture is heated by the laser to the point that the hydrogen is reduced and carbon is oxidized.
Eikka
5 / 5 (1) Aug 28, 2013
Of course, the problem is always in how to get the carbon.

It's not really a hydrogen economy if you have to mine for coal to produce hydrogen at a loss. Thermodynamically speaking, you aren't getting more hydrogen out than you put carbon in.
antialias_physorg
5 / 5 (1) Aug 29, 2013
Depends. Since it's only a catalyst the usage of carbon should be minimal. And it's not really the carbon that is the problem in a carbon economy, but the CO2 produced. Having carbon in the mix as a catalyst without producing CO2 (or other greenhouse gases) is fine.

However, I suspect exposure to the laser would combust some of the carbon. And you can't really have this process work under oxygen-free conditions, since you always liberate O2 along with the hydrogen from water. So there may be a few caveats attached to this method.

Another thing is that lasers aren't typically very efficient (depending on the type only a few percent of the input energy gets converted to laser light). So the energy conversion efficiency of the whole process needs to be explored.

For comparison: Photobiological systems are 7-10% efficient in producing hydrogen
(Various cataytic systems are more efficient, but that's what they're trying to replace here so a comparison wouldn't be fair).
Eikka
not rated yet Sep 04, 2013
Since it's only a catalyst the usage of carbon should be minimal.


It's not really a catalyst because the carbon gets consumed. It can be thought of as such if you could recycle the CO2 back to carbon, but that's a whole other can of worms.

However, I suspect exposure to the laser would combust some of the carbon.


The whole process works by combusting the carbon with the oxygen coming off of the water. The energy from the combustion is collected in the form of hydrogen gas. The energy pumped in with the laser is lost as heat, because the chemical exchange of oxygen doesn't permit the system to store any energy that doesn't come from the carbon. The only purpose of the laser is to break the energy barrier that keeps the oxygen atom bound to the hydrogen, which is not much because the carbon is there ready to snatch the oxygen atom.

In other words, the biggest problem of the system is the massive demand for carbon. It's a method of burning coal in water.