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Published online 31 July 2008 | Nature | doi:10.1038/news.2008.996
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Catalyst heralded as solar-power breakthrough
Add simple metal salts to a beaker of water, apply a current, and watch the clean, green hydrogen bubble forth.
It sounds almost too good to be true — but chemists believe they have made a key breakthrough that would allow them to mimic photosynthesis and solve the world’s energy crisis.
Daniel Nocera and Matthew Kanan at the Massachusetts Institute of Technology in Cambridge have discovered a simple, inexpensive system that can help to split water to produce oxygen and hydrogen gas.
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I would like to see an energy analysis comparing this technology with straight hydrolysis. What fraction of the output energy [in H and O] originated from sunlight?
Imprison Co as Sargeson's self-assembling (dinosar) ligand. That affords two sites for (spacer) linkage to -Si(OR)3, vinyl sulfone, azide, whatever groups. Do nitrene photochemistry or click chemistry onto a polymer with the azide. Brute force or elegant, bond it to fibrous conductive polypyrrole and there is no inert substrate hogging mass and volume. https://www.chem.ubc.ca/faculty/wassell/CHEM310/Experiment_12/Experiment12.htm and references therein for electron transfer kinetics
Similar to what Roger Dittmann wrote, I would like to see an energy use comparison between this process and general photosynthetic photolysis.
Is it the future that knocks in our door? If so, what marvelous! Energy from … water! Water: for drink, bath, irrigation, and for power. It is like magic!
Is it the future that knocks in our door? If so, what marvelous! Energy from … water! Water: for drink, bath, irrigation, and for power. It is like magic!
"It sounds almost too good to be true". Agreed. Let's see this replicated, including verifying the claim that only small voltages are needed to make if break water. I also call for an enery usage audit, as well as extended tests to determine how and at what rate it degrades. (I don't for a second believe that this system cannot degrade, but it is does so at a low enough rate this will be a maintainable way to produce hydrogen.)
The article implies that electrolysis + fuel cells could be used as "batteries" to smooth out fluctuations from renewable electricity. Assuming this can be done, how does this combination compare in cost and efficiency to other "batteries" like compressed air storage? Even if the combination is unfavorable to hydrogen for power storage, the pure hydrogen and oxygen gases generated (again, assuming that they can be separated per the article) have commercial value. If electrolysis is cheap enough, it could replace other gas production processes, such as fossil hydrocarbons for hydrogen and air liquidification for oxygen.
I agree that I would like to see some data on the voltage requirements for this catalyst. In the story the writer says that "normal" water electrolysis requires high voltages and this is untrue. The voltage required to electrolyze a solution of water and an electrolyte is determined by the electrolyte. H2So4 in water for example is 1.23 volts I believe, hardly "high voltage". The author states that in "normal" electrolysis expensive platinum electrodes are required. This is also untrue. While it is true that an inert metal is needed so that the metal is not consumed in the reaction it doesn't have to be an expensive metal. Nickel is just fine, or even a high nickel content stainless and that is hardly expensive. Like platinum or ruthenium or gold, nickel also provides a small catalytic effect on the reaction. Another curious fact is that this catalyst claims to replicate photosynthesis but I don't feel that this is an accurate analogy at all. Photosynthesis converts the sun's energy directly within the photosynthesis reaction via chlorophyll while this reaction depends on electrical current from solar cells. "Normal" electrolysis cells can operate just fine on solar or wind energy so this seems to me to be just another modified electrolysis cell based on the description above. Also, the photosynthesis reaction converts water and carbon dioxide into carbohydrates and releases oxygen as a by-product, This process is much more like normal electrolysis in that the products are those normally associated with the direct decomposition of water via electrolysis and not a novel adaptation of the photosynthesis process. As far as the action of the catalyst forming a deposition while in operation and then dissolving back into solution when power is off, I developed a similar catalyst 5 or 6 years ago. I never published on it other than on the web but I could show you that description which sounds almost identical. My point is that, from the data provided, this does not seem to be a very novel process whether it is a new catalyst or not and it seems almost totally unrelated to photosynthesis and I would have expected Nature to do a more thorough examination of the process before jumping on the publicity bandwagon like Fox or CNN.
I am somewhat putting the same questions raised by Mike Johnston, but in diifferent sense.The catalytic decomposition of water by this approach is rather acceptable within the limits of electrochemistry.To use noble metals if seems expensive, ultra-loading of such metals in engineered catalysts is till possible.I think Mike is somewhat aggressive, as use of non noble metals leads to degradation of the performance of the cell and therefore to improve their catalytic utility in engineered catalysts is a continious R&D activity.Even though this perticular invention incleuds some charge transfer anology of photosynthesis,it meerly not replecting the process of photosynthesis.But it may prove a better photolytic route to produce hydrogen and oxygen fuels where the required voltage of 1.23V is rather high. But the corrosion of electrodes, kinetics of reactions,efficiency of electrolytic cell are the questions remains to be unanswered. Vilas Patil