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Researchers Discover Inexpensive Catalyst That Generates Hydrogen from Buffered Water or Sea Water

Karunadasa
[(PY5Me2)Mo(CF3SO3)]1+ reacts with water to form
[(PY5Me2)MoO]2+ and H2. Credit: Nature, Karunadasa et al. Click to enlarge.

A team of researchers with the US Department of Energy’s (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley has discovered an inexpensive metal catalyst that can effectively generate hydrogen gas from water at neutral pH or from sea water.

The new proton reduction catalyst is based on a molybdenum-oxo metal complex that is about 70 times cheaper than platinum—currently the most widely used metal catalyst for splitting the water molecule—according to Hemamala Karunadasa, one of the co-discoverers of this complex and lead author of a paper describing the work published 29 April in the journal Nature.

In addition, our catalyst does not require organic additives, and can operate in neutral water, even if it is dirty, and can operate in sea water, the most abundant source of hydrogen on earth and a natural electrolyte. These qualities make our catalyst ideal for renewable energy and sustainable chemistry.

—Hemamala Karunadasa

The electrolytic production of water requires a water-splitting catalyst. Plants uses hydrogenases during photosynthesis; however, these enzymes are unstable and easily deactivated when removed from their native environment. Human activities seem to demand a stable metal catalyst that can operate under non-biological settings.

Metal catalysts are commercially available, but they are low valence precious metals the high costs of which make their widespread use prohibitive. For example, platinum, the best of them, costs some $2,000 an ounce.

The basic scientific challenge has been to create earth-abundant molecular systems that produce hydrogen from water with high catalytic activity and stability. We believe our discovery of a molecular molybdenum-oxo catalyst for generating hydrogen from water without the use of additional acids or organic co-solvents establishes a new chemical paradigm for creating reduction catalysts that are highly active and robust in aqueous media.

—Christopher Chang, co-author

The molybdenum-oxo complex that Karunadasa, Chang and Jeffrey Long discovered is a high valence metal named (PY5Me2)Mo-oxo. In their studies, the research team found that this complex catalyzes the generation of hydrogen from neutral buffered water or even sea water with a turnover frequency of 2.4 moles of hydrogen per mole of catalyst per second.

The work shows that high-valency metal-oxo species can be used to create reduction catalysts that are robust and functional in water, the authors said, a concept that has broad implications for the design of ‘green’ and sustainable chemistry cycles.

This metal-oxo complex represents a distinct molecular motif for reduction catalysis that has high activity and stability in water. We are now focused on modifying the PY5Me ligand portion of the complex and investigating other metal complexes based on similar ligand platforms to further facilitate electrical charge-driven as well as light-driven catalytic processes. Our particular emphasis is on chemistry relevant to sustainable energy cycles

—Jeffrey Long

This research was supported in part by the DOE Office of Science through Berkeley Lab’s Helios Solar Energy Research Center, and in part by a grant from the National Science Foundation.

Resources

  • Hemamala I. Karunadasa, Christopher J. Chang & Jeffrey R. Long (2010) A molecular molybdenum-oxo catalyst for generating hydrogen from water. Nature 464, 1329-1333 doi: 10.1038/nature08969

Comments

GdB

How much power is required? Or to the point what is the $/km cost?

Sounds like all the Hydrogen fuel issues have had enough breakthroughs recently to maybe allow competitive automotive application.

HealthyBreeze

To play the cynic for a moment; what I'm hearing them say is that this is a cheaper (hence more scalable) way to turn half the high quality electricity into waste heat so you can make some difficult-and-expensive-to-store H2. Is that what y'all are hearing? Give us cheaper, lighter, high-powered batteries and we can make much better use of that high quality electricity.

Sanity Chk

Healthy, you are right on the mark. Aside from wasting efficiency using electricity to make H2, you've got storage & distribution issues to tackle if transportation is the end use. Makes no sense to go down that path when batteries and electric motors do the job with greater efficiency.

People who promote the use of H2 seem to neglect the fact that it is a potent GHG, and is very difficult to contain due to its small molecular size.

3PeaceSweet

Hydrogen is a silly way to store energy. We can store energy by not burning fossil fuels as they are a store of energy as well as a source.

If we do eventually need to store electricity (a windy night when demand is low) a much better way to do it is using pumped storage or heat pumps to store heat via heat pumps in hot water tanks which are also required for solar thermal which is far cheaper (at the moment) than solar PV.

ToppaTom

I am encouraged to see that the above Posters understand what catalist means.

Maybe these snake oil salesmen will back off.

Maybe we won't see an invention that provides all the electrical power you need by replacing gold ($2000/oz) with brass ($0.02/oz) in new, low cost connectors for BEVs.

ToppaTom

And they know how to spell it.

wintermane2000

Ok folks what this means in english is they will be able to use BULK materials to generate massive amounts of cheaper h2 from seawater and wastewater and various energy imputs.

Basicaly they can make gigatons of the stuff.

Question is does it require more power to make h2 using this stuff or not and are the other forms they are working on hold the hope for lower energy needs in making h2 this way?

Engineer-Poet

It's doubtful that H2 requires significantly more or less energy to make with this catalyst than e.g. platinum. On the other hand, having a cheap catalyst which can just be slathered on and used at low current densities is going to make electrolysis cells a lot cheaper.

Hydrogen made from electricity is still going to cost a lot more than electricity; Bossel's Law still holds.  What this might do is allow excess RE to make chemical feedstock for other things; e.g. hydrogen for hydro-cracking and deoxygenation of triglycerides to make green diesel and propane instead of FAME and glycerol.

wintermane2000

Well dont forget because of pipelines its very likely if BULK h2 from electricity realy catches on they will make it only in places where they can nail VERY cheap power same as alumiuum production.

ToppaTom

It's doubtful that H2 requires significantly more or less energy to make with this catalyst than e.g. platinum. They do not even claim this.

I have NEVER heard that the conversion of electricity (which is EASILY transportable) is costly because of the catalyst.

They do not answer the "Question is does it require more power to make h2 using this stuff or not"

If they do not say so - it surely does not.

sulleny

H2 centrally produced and distributed in the old "gas station model" is big oil's attempt to hang on to fuel monopolies. A low cost catalyst using renewable electric energy to produce H2 in situ - is another story - both for mobile and fixed site applications.

Let's see, 85% greenhouse effect is due to water vapor. Longer residence GHGs are:

CO2 - 9%
CH4 - 3%
CFS - 2.1%
N2O - 0.9%

How is H2 a greenhouse gas again?

Ole Grampa

Hey Harvey D, aren't you going to remind us that hydrogen power can't work?

Sanity Chk

I agree with the notion that the fossil companies have stoked the hydrogen interest through advertising and other means to maintain their current control over energy production & distribution.

H2 is an indirect GHG, i.e. it creates GHGs by reacting with other molecules in our atmosphere. Check out the "others" link under the "Greenhouse Gases" group on this site:

http://www.ghgonline.org/index.htm

It is not a significant contributor at the moment, however before basing a decision about using it on a large scale, we had better understand its dynamic within our atmospheric soup. This includes factors such as staying power, potency, emissions sources, et al.

Vince

A common myth is that it takes too much energy to make hydrogen. Energy is required to make all fuels used today. Expending energy to separate hydrogen from a primary energy resource is worthwhile if the resulting hydrogen has benefits that outweigh the energy and financial costs of production. We accept a similar and often larger energy penalty in producing electricity for the same reason – the convenience and utility of having electricity is much greater than the convenience and utility of the original coal or other fuel that was used to make the electricity. Any new process that allows us to produce hydrogen in a more efficient manner is definitely worth pursuing.

The energy required to produce hydrogen at atmospheric pressure via electrolysis (assuming 1.23 V) is about 32.9 kWh/kg. A kilogram is about 2.2 lb. For 1 mole (2 g) of hydrogen the energy is about 0.0660 kWh/mole. Compressing or liquefying the hydrogen would take additional energy. One company produces hydrogen through electrolysis at about 7,000psi at an energy usage of about 60kWh/kg H (2).

Because a Watt is Voltage x Current, this is equivalent to Power x Rate x Time. The power in this case is the voltage required to split water into hydrogen and oxygen (1.23 V at 25C). The rate is the current flow and relates directly to how fast hydrogen is produced. Time, of course, is how long the reaction runs. It turns out that voltage and current flow are interrelated. To run the water splitting reaction at a higher rate (generating more hydrogen in a given time), more voltage must be applied (similar to pushing down on the accelerator of a car; more gas is used to make the car go faster.) For commercial electrolysis systems that operate at about 1 A/cm2, a voltage of 1.75 V is required. This translates into about 46.8 kW-hr/kg, which corresponds to an energy efficiency of 70%.

Is hydrogen safe?

Most fuels have high energy content and must be handled properly to be safe. Hydrogen is no different. In general, hydrogen is neither more nor less inherently hazardous than gasoline, propane, or methane. As with any fuel, safe handling depends on knowledge of its particular physical, chemical, and thermal properties and consideration of safe ways to accommodate those properties. Hydrogen, handled with this knowledge, is a safe fuel.

Hydrogen has been safely produced, stored, transported, and used in large amounts in industry by following standard practices that have been established in the past 50 years. These practices can be emulated in non-industrial uses of hydrogen to attain the same level of routine safety.

While hydrogen has a wider flammability range than gasoline, the range is only a piece of the story when considering the likelihood of a fire resulting from hydrogen escaping into the atmosphere. Each fuel has different properties that must be considered along with flammability range.

For example: Gasoline's narrow flammability range is a bit misleading, since this range can easily and often be reached through normal consumer handling of gasoline and certainly if spilled. There are of course gasoline fires but, as we know, fires certainly don't occur every time gasoline vapors are released to the open air, because the vapors fail to find an ignition source in time.

Hydrogen has a wider flammability range, but because it is lighter than air (50 times lighter than gasoline vapors and even lighter than helium) and diffuses 12 times faster than gasoline vapors do, it is very difficult for hydrogen gas to find a suitable ignition source in an open environment, like a fueling station.

Sources
Proton Energy Systems
Honda Media Newsroom
US Environmental Protection Agency
National Hydrogen Association
Shell Hydrogen LLC

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