Producing hydrogen from sea water

Chemistry World ^ | 28 April 2010 | Mike Brown

[neverdem]

A new catalyst that generates hydrogen from sea water has been developed by scientists in the US. This new metal-oxo complex displays high catalytic activity and stability, whilst being low cost, the researchers say.

Hydrogen is very attractive as a clean source of power. Currently, it is produced by natural gas reforming - where steam is reacted with methane in the presence of a nickel catalyst to form hydrogen - but this method produces the greenhouse gas carbon dioxide.

Jeffrey Long and colleagues from the University of California, Berkeley, prepared a simple molybdenum-oxo complex that can serve as an electrocatalyst, reducing the energy required to generate hydrogen from water on a mercury electrode. As an abundant metal, molybdenum is much cheaper than precious metal catalysts where the costs associated with large scale hydrogen production would be high.

The team's molybdenum-oxo species generates hydrogen from sea water

© Nature

Long explains that the stability of the catalyst is due to a ligand that bonds to the molybdenum in five places (pentadentate) making it a very strong complex. 'The molecule is very robust and is stable in aqueous conditions for long periods of time so we don't see degradation of the catalytic activity over three days of running the reaction,' he says.  

Significantly, Long's catalyst is also stable in the presence of impurities that can be found in the ocean, meaning that sea water can be used without pre-treatment. The team used a sample of California sea water in the system and found the results to be similar to the results obtained for water at neutral pH. In addition, no other electrolyte is necessary when using sea water, which helps reduce costs and removes any need for organic acids or solvents that could degrade the catalyst.

'The work clearly demonstrates that the molybdenum-oxo complex explored shows good catalytic activity, with at least an order of magnitude higher turnover frequency [the speed at which a catalytic cycle is completed] than alternative catalysts quoted,' says Bruce Ewan, an expert in hydrogen production and renewable energy at the University of Sheffield, UK.   'This new catalyst also opens up new possibilities as a catalytic agent in other proton reducing scenarios,' he adds.

Long and his team hope to develop this system so that 'in the future a catalyst like this could be used in conjunction with a solar cell to produce hydrogen,' he explains. The team is now working on modifying the catalyst to reduce the potential at which the electrochemical reaction proceeds and make the system more efficient.

 

References

H I Karunadasa, C J Chang and J R Long, Nature, 2010, DOI: 10.1038/nature08969

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[Royal Wulff]

Seawater is 1 ppm uranium...they’d be better off extracting uranium from seawater.

[babygene]

ping

[Recon Dad]

Just think how much more energy can be gained it they use the waters of the Gulf of Mexico!

[Lion Den Dan]

And whence comes the energy to conduct this catalytic reaction? What becomes of the expended catalyst and is it toxic. Molydenum, what is the energy cost to produce that and is it not toxic to a degree????? Nothing without a price.

[IamConservative]

Another claiming to have circumvented the laws of thermodynamics?

[reg45]

If we use sea water to create hydrogen, and make the oceans lower, that should help counteract the melting ice caps from global warming. We will live!

Oops! You missed a step. When the hydrogen is consumed as fuel - a very good thing - water is formed in the atmosphere which precipitates as rain. This rain will eventually wind up in the oceans - they get refilled. We therefore have a virtually perpetual fuel source.

[reg45]

The nature of a catalytic agent is that it is not consumed in the reaction. BTW, I have been an advocate of hydrogen as a fuel for forty years.

[conservatism_IS_compassion]

in a 100 years, i have no doubt in my mind that the future generation of environmentalist will find fault in the technology thats powering society, even if we adopt everything they support now e.g ethanol, solar panel.

That's because they are progressives" - and therefore they cannot have an end point.

"Change" is their entire philosophy.

[FreePaul]

There are many ways to produce hydrogen. Is this cheaper and easier than other methods? Is this cheaper than "fossil" fuels?

As with all hydrogen schemes the question as to distribution methods will rear it's head. Hydrogen is not an easy gas to handle or transport.

[norwaypinesavage]

"The half life of a water molecule in the atmosphere is about a week, a molecule of CO2 about a century"

Use of the term "half-life" to describe ingredients in a system that is largely steady-state is very simplistic. Water simply changes state regularly, and there is no chemical alteration of it. CO2 is chemically altered when it is generated by burning fuel and is therefore not in the same class as water for your analogy.

[bert]

.....tin foil....

Aluminum foil?

[neverdem]

The process is called electrolysis.

Finding the right catalyst will determine whether the electrolysis of water for using hydrogen as a fuel is economically viable or not, IMHO.

[dangus]

LOL! They actually said, “whilst?”

[dangus]

Nope. Producing is fine. H+ is simply a proton. H2 is a molecule. By “Hydrogen,” they mean H2, not protons. Water is not H2. It does not contain H2.

[dangus]

You don’t extract something unless it exists already in what you extract it from.

[ASOC]

sorry,

reynolds wrap?

al

commonly called tin foil in the hinderlans were I grew up

[ASOC]

ya, that can happen (kof kof) by accident

dry ice does the same thing is much safer

lye (drano) is dangerous if one is not careful 0

[ckilmer]

I'm no scientist or chemist and I didn't study this stuff much in school and that was long ago. So would someone kindly school me.

My understanding is that the salt NaCl in salt water is in ion form. Something like Na+ and Cl- where the Na+ has an extra electron and the Cl- is lacking an electron.

The salt in ion form is stable in water.

However, the Na sodium ion stripped of its electron--in the presence of water H2O-- is exothermic .... well its explosive. If you do a google search of sodium water reaction youtube-- You can find all kinds of kids blowing up trashcans of water with sodium

So couldn't you just get a controlled combustion by stripping the sodium ion Na+ in situ --while its in water --of its extra electron. The only similarity to a gasoline combustion -- is that you'd have to add extra energy for it to work but the resulting explosion would be exothermic--ie you'd get more energy out.

You might do this by bombarding the salt water with radio waves at the resonance for sodium so as to create a synthetic catalyst.

Kanzius bombarded saltwater at 13.56 MHz -- the Nuclear Magnetic Resonance for Oxygen--which released the hydrogen out of H20. (Likely because the radio wave also heated up Na+ in solution--as would a microwave oven heat a metal.) But what would happen if you bombarded saltwater at the NMR for sodium.

Just a thought.

But the gist of the question is this: why can't you make a controlled combustion with salt water by stripping out the extra electron from the Na+ sodium ion.

(There would likely be three problems 1.)stripping the ion. 2.)controlling the combustion 3.) sorting out the waste)