An FESEM image of a Ti-Fe-O nanotube array. Click to enlarge.
Posted on 08/16/2007 11:18:54 AM PDT by Uncledave
Researchers Developing Nanotube Arrays to Produce Hydrogen From Visible Light 15 August 2007
A research group headed by Professor of Electrical Engineering Craig Grimes at Penn State University is developing an inexpensive and easily scalable technique for water photoelectrolysis—the splitting of water into hydrogen and oxygen using light energy.
In a paper published online in Nano Letters, lead author Gopal K. Mor, along with Haripriya E. Prakasam, Oomman K. Varghese, Kathik Shankar, and Grimes, describe the fabrication of thin films made of self-aligned, vertically oriented titanium iron oxide (Ti-Fe-O) nanotube arrays that demonstrate the ability to split water under natural sunlight.
Previously, the Penn State scientists had reported the development of titania nanotube arrays with a photoconversion efficiency of 16.5% under ultraviolet light. Titanium oxide (TiO2), which is commonly used in white paints and sunscreens, has excellent charge-transfer properties and corrosion stability, making it a likely candidate for cheap and long lasting solar cells. However, as ultraviolet light contains only about 5% of the solar spectrum energy, the researchers needed to finds a means to move the materials band gap into the visible spectrum.
They speculated that by doping the TiO2 film with a form of iron called hematite, a low band gap semiconductor material, they could capture a much larger portion of the solar spectrum. The researchers created Ti-Fe metal films by sputtered titanium and iron targets on fluorine-doped tin oxide coated glass substrates. The films were anodized in an ethylene glycol solution and then crystallized by oxygen annealing for 2 hours. They studied a variety of films of differing thicknesses and varying iron content. In this paper they report a photocurrent of 2 mA/cm2 with a sustained, with a time-energy normalized hydrogen evolution rate of 7.1 mL/W·hr and a photoconversion rate of 1.5%, the second-highest rate achieved with an iron oxide related material.
The team is now looking into optimizing the nanotube architecture to overcome the low electron-hole mobility of iron. By reducing the wall thickness of the Ti-Fe-O nanotubes to correspond to the hole diffusion length of iron which is around 4nm, the researchers hope to reach an efficiency closer to the 12.9% theoretical maximum for materials with the band gap of hematite.
As I see it, we are a couple of problems away from having something that will revolutionize the field of hydrogen generation by use of solar energy. —Craig Grimes
An FESEM image of a Ti-Fe-O nanotube array. Click to enlarge.
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How does a photon of visible light turn into an atom of hydrogen?
....And Gore said, “Let there be Hydrogen!” and there was hydrogen...........
Same way water turns into wine............ST. Algore.........
Thanks for the ping.
The key here is the scalability. This development is highly significant.
We are just now beginning to glimpse a future where we are independent of islamofascist oil. It will cost us, but it will be worth it in the long run.
It doesn’t. But your commentary on the inability of reporters to generate a meaningful headline is duly noted.
Did you happen to see the other story at Greencar about the 200+mph fuel cell car test at Bonneville?......
a form of iron called hematite, a low band gap semiconductor material,
***I didn’t know Iron was considered a semiconductor. I suppose you could consider Carbon a high bandgap semiconductor, so Iron by that definition would be a low bandgap semi...
A research group headed by Professor of Electrical Engineering Craig Grimes at Penn State University is developing an inexpensive and easily scalable technique for water photoelectrolysis—the splitting of water into hydrogen and oxygen using light energy.
Just accept it.
All green plants do this via photosynthesis. They use sunlight to split water into Hydrogen and Oxygen. The plants want to keep the Hydrogen to make carbohydrates and release the Oxygen back into nature.
Right now, hydrolysis--breaking up water molecules--requires more electricity than it's worth. But if we can ever imitate plants with a semi-efficient way to use sunlight to break out Hydrogen from water (and release Oxygen as a byproduct) it would be world-changing.
So that would be roughly 7 liters of hydrogen per square meter of sun light (lot of assumptions in that number)? Maybe 100 L per day?
Hope the efficiency improves a couple orders of magnitude. At that rate, gonna take a LOT of ground to make enough hydrogen to power this nation.
Though I suppose this could also lead to advances in electrolysis production of hydrogen (say from nuke power).
Well, criminy! We can fix that! Let's just uncork and release all the R-12 we can, get that UV level up where it's useful!
“....And Gore said, “Let there be Hydrogen!” and there was hydrogen...........”
We already did hydrogen, the Hindenburg.
Oh, the humanity!
By interacting with a photo-reactive catalyst which goes on to dissociate water atoms.
They are not creating hydrogen from light, they are using the light to break the hydrogen-oxygen bonds in water to create free hydrogen and oxygen.
One then vents the oxygen and captures the hydrogen for fuel.
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