Skip to comments.Splitting the sea
Posted on 06/02/2013 10:02:26 PM PDT by neverdem
Scientists in Australia are closer to harvesting hydrogen from two of the most abundant and naturally occurring resources in our environment seawater and sunlight.
Water oxidation, the first part of the water splitting reaction that can produce hydrogen, is difficult as it is so kinetically unfavourable. Using photocatalysts to overcome this energy barrier is appealing as sunlight can supply the required energy rather than needing electrical or thermal energy.
Unlike some photocatalytic water oxidation methods that use catalysts mounted on a semiconductor to form an electrode, a team, led by Jun Chen and Gerhard Swiegers, from the University of Wollongong, Australia, have shown that a manganese-porphyrin photocatalyst embedded in a transparent, intrinsically conductive polymer can successfully oxidise water. The polymer promotes charge transfer between the embedded photocatalysts and enables an unusually low onset potential (the point at which a photocurrent is observed).
Another other important benefit of the system is its high selectivity for water. In systems that use semiconductors, the holes on semiconductor surfaces extract electrons from chloride ions, as well as water. This leads to the formation of chlorine gas in non-pure water sources such as seawater. Avoiding chlorine gas production was one of the main aims of this project as its toxicity can cause health and safety issues, explains Chen.
Mauro Carraro from the University of Padova, Italy, who also studies water splitting, was impressed by the remarkable selectivity of the catalyst. The process is a step further towards the design of an effective artificial leaf, he adds.
The research team now plan to investigate how to incorporate the technology into a functional hydrogen fuel cell.
J Chen et al, Chem. Sci., 2013, DOI: 10.1039/c3sc50812a
Just no subsidies for commercial operations!
Why not just use photoelectric cells to generate electricity to split the water molecule? The primary drawback to things like photoelectric and wind power is that they’re unreliable. But with this type of process you don’t need 100 percent reliability because the end product is storable. The same would apply to nuclear power. If people find it so objectionable in their backyards, put the generators in places where no one lives and use them exclusively as an energy source for producing storable synthetic fuels.
lots of candidates for a better photo catalytic reaction.
with this much smoke there may be fire sometime in the next couple years.
True enough. Or let wind turbines and solar collect CO2 out of the atmosphere and liquify it to store underground - and this would “cleanse” our nat gas and coal plants. Incorporating unreliable power into the grid is more expensive than it is worth.
The Second Law of Thermodynamics says you have to pay entropy its due with each conversion of energy from one form to another. I think generating hydrogen in situ is more efficient. The question is cost, IMHO.
It's highly inefficient, and very expensive. Only a small fraction of the available solar energy actually goes into the production of hydrogen. Photocells deteriorate and become even more inefficient, and they also fail regularly. Recently produced, so called "low cost" photo cells have had failure rates as high as 25 percent in the FIRST year. The electrolysis cells require expensive metals such as gold or platinum to reduce their deterioration, and often some sort of chemicals in the water to enhance conductivity. The hydrogen must be compressed for storage and transportation, which also takes even more energy.
Electrical energy delivered to my house already costs about double the price of fuel in my car tank, per BTU. Solar electricity is the highest cost electricity to produce. Add to that the cost of electrolysis and compression, and you have a super dud.
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