Researchers Develop and Synthesize Stable Inorganic Catalyst for Artificial Photosynthesis
25 March 2008
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| A tetraruthenium polyoxometalate cluster (Ru blue, O red, Si yellow, W black) catalyzes the rapid oxidation of H2O to O2 in water at ambient temperature, and shows considerable stability under turnover conditions. Click to enlarge. |
A team of researchers from Forschungszentrum Jülich in Germany and Emory University in the US have synthesized a stable inorganic metal oxide cluster which catalyzes the fast and effective oxidation of water to oxygen. The work, a step toward artificial photosynthesis and the efficient production of hydrogen through solar energy, is published online in the journal Angewandte Chemie and is rated as a “very important paper”.
One of the barriers to achieving artificial photosynthesis is the formation of aggressive substances in the process of water oxidation. Plants solve this problem by constantly repairing and replacing their green catalysts. Artificial photosynthesis, however, depends on more stable catalysts.
To address this, the research team developed and synthesized a new inorganic metal oxide cluster with a core consisting of four ions of the rare transition metal ruthenium. This catalyzes the oxidation of water to oxygen while remaining stable itself.
Our water-soluble tetraruthenium complex displays its effects in aqueous solution already at ambient temperature. In contrast to other molecular catalysts for water oxidation, our catalyst does not contain any organic components. This is why it is so stable. Now the challenge is to integrate this ruthenium complex into photoactive systems, which convert solar energy into chemical energy.
—Prof. Paul Kögerler from the Jülich Institute of Solid State Research
For this work, the energy for the process was obtained from a chemical oxidant. Prof. Kögerler synthesized and characterized the catalyst cluster together with his colleague Dr. Bogdan Botar. Catalytic measurements were carried out at Emory University.
Resources
Yurii V. Geletii, Bogdan Botar, Paul Kögerler, Daniel A. Hillesheim, Djamaladdin G. Musaev, and Craig L. Hill; An All-Inorganic, Stable, and Highly Active Tetraruthenium Homogeneous Catalyst for Water Oxidation; Angewandte Chemie, DOI: 10.1002/ange.200705652
Why is there such intrest in solar to hydrogen directly, if they can't do it as efficiently and as versatilely as solar-electric to electrolysis then I don't see the point.
Posted by: Ben | 25 March 2008 at 09:19 AM
Unfortunately we have a lot of oxygen available. But water oxydation is a good trial to prepare the future Photochemistry Olympic Games : water reduction!! Prepare UV or Gamma Ray lamps and secret catalysts. We accept acidic or basic pH conditions. Alchemists are disqualified, too easy!
Posted by: raymond bonnaterre | 25 March 2008 at 09:54 AM
@ Ben -
it's called basic research and may take decades to reach commercial applications. This particular molecule contains rare minerals Ruthenium and Tungsten, which would limit it to highly specialized uses such as generating small quantities of fuel to support equipment on another planet, moon or asteroid that contains water ice.
Also, suppose astronomers discover a sizeable asteroid composed of ice and dust is on a course that might cause it to collide with our planet decades into the future. Now suppose that a spacecraft is sent to land on that asteroid, for the sole purpose of gradually nudging it off course.
It could mine some of the ice, split it using the weak available sunlight and a molecule like this one and store the hydrogen and oxygen. Once enough is collected, the two would be combined in a fuel cell and the water vapor vented into space where it immediately freezes. No matter, as long as it doesn't end up back on the asteroid, the trajectory will have been very slightly altered. Rinse and repeat for several years or decades, possibly with a succession of spacecraft, and voila - calamity avoided.
We last had a sizeable asteroid impact/atmospheric explosion in Tunguska (Siberia) in 1908, and a near miss in 2004. If one were to hit near a populated area, it would cause massive damage comparable only to a major volcanic eruption, tsunami or nuclear war.
http://en.wikipedia.org/wiki/Tunguska_event
http://en.wikipedia.org/wiki/2004_XP14
Posted by: Rafael Seidl | 25 March 2008 at 10:23 AM
I've always thought that it should be relatively easy for a photo-catalyst to synthesize CH4 from H2O and C. Perhaps this is a step in that direction?
Posted by: GreenPlease | 25 March 2008 at 01:42 PM
Ben, You can store hydrogen, and also transport it. thus you can use the sun's energy when it's not shining.
Posted by: danm | 25 March 2008 at 03:12 PM
One use of hydrogen from splitting water with solar is in fertilizer production. Currently, we make nitrogen fertilizers (ammonium nitrate) using natural gas as the H2 source to convert stable N2 in the air into NH3, in the catalyst-dependent Haber process. Using solar we should be able to produce large amounts of nitrogen fertilizer without access to fossil fuels - after all, that's what nitrogen-fixing bacteria and their plant associates (peas, for example) do. Solar hydrogen has many other possible industrial uses.
So, should solar hydrogen be produced using bulk electrolysis or direct, molecular-level effects? The answer might be the in-between region of nanomaterials, whose dimensions are much bigger than single atoms but which still show unique, size-dependent effects not found in bulk: "QuantumSphere NiFe Nanoparticle Electrodes Push Electrolyzer Efficiency to 85%",
http://www.greencarcongress.com/2008/03/quantumsphere-n.html
For some applications, real photosynthesis using algal cells is the best way to go. We might at some point be able to directly pull CO2 out of the air, react it with hydrogen from water, and make our own methane, methanol, or long-chain hydrocarbon from the air - but we can get algal ponds or algal bioreactors to do that today.
Posted by: ike | 25 March 2008 at 11:52 PM
I agree with RS on this one. Basic research can lead to many things. Showing that something can be done, gets people thinking in different ways.
The asteroid scenario is real. There is suppose to be a near miss in the next 20 years or so and that will tell us if it will hit later when it passes by again less than 10 years later. Deflecting it with propulsion would be a good way to avoid major problems.
Posted by: sjc | 02 April 2008 at 09:54 PM