Novel alloy could produce hydrogen fuel from sunlight

Aug 30, 2011

Scientists from the University of Kentucky and the University of Louisville have determined that an inexpensive semiconductor material can be "tweaked" to generate hydrogen from water using sunlight.

The research, funded by the U.S. Department of Energy, was led by Professors Madhu Menon and R. Michael Sheetz at the UK Center for Computational Sciences, and Professor Mahendra Sunkara and graduate student Chandrashekhar Pendyala at the UofL Conn Center for Renewable Energy Research. Their findings were published Aug. 1 in the Physical Review Journal (Phys Rev B 84, 075304).

The researchers say their findings are a triumph for computational sciences, one that could potentially have for the future of solar energy.

Using state-of-the-art theoretical computations, the UK-UofL team demonstrated that an alloy formed by a 2 percent substitution of antimony (Sb) in gallium nitride (GaN) has the right electrical properties to enable solar to split into hydrogen and oxygen, a process known as photoelectrochemical (PEC) . When the alloy is immersed in water and exposed to sunlight, the between the hydrogen and in water is broken. The hydrogen can then be collected.

"Previous research on PEC has focused on ," Menon said. "We decided to go against the conventional wisdom and start with some easy-to-produce materials, even if they lacked the right arrangement of electrons to meet PEC criteria. Our goal was to see if a minimal 'tweaking' of the electronic arrangement in these materials would accomplish the desired results."

is a semiconductor that has been in widespread use to make bright-light LEDs since the 1990s. Antimony is a metalloid element that has been in increased demand in recent years for applications in microelectronics. The GaN-Sb alloy is the first simple, easy-to-produce material to be considered a candidate for PEC water splitting. The alloy functions as a catalyst in the PEC reaction, meaning that it is not consumed and may be reused indefinitely. UofL and UK researchers are currently working toward producing the alloy and testing its ability to convert solar energy to hydrogen.

Hydrogen has long been touted as a likely key component in the transition to cleaner energy sources. It can be used in fuel cells to generate electricity, burned to produce heat, and utilized in internal-combustion engines to power vehicles. When combusted, hydrogen combines with oxygen to form water vapor as its only waste product. Hydrogen also has wide-ranging applications in science and industry.

Because pure hydrogen gas is not found in free abundance on Earth, it must be manufactured by unlocking it from other compounds. Thus, hydrogen is not considered an energy source, but rather an "energy carrier." Currently, it takes a large amount of electricity to generate hydrogen by water splitting. As a consequence, most of the hydrogen manufactured today is derived from non-renewable sources such as coal and natural gas.

Sunkara says the GaN-Sb alloy has the potential to convert solar energy into an economical, carbon-free source for hydrogen.

" production now involves a large amount of CO2 emissions," Sunkara said. "Once this alloy material is widely available, it could conceivably be used to make zero-emissions fuel for powering homes and cars and to heat homes."

Menon says the research should attract the interest of other scientists across a variety of disciplines.

"Photocatalysis is currently one of the hottest topics in science," Menon said. "We expect the present work to have a wide appeal in the community spanning chemistry, physics and engineering."

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Provided by University of Kentucky

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User comments : 16

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Bob_B
not rated yet Aug 30, 2011
Could this be the rooftop collector we need for hydrogen, or is it going to be a huge device?
Star_Gazer
not rated yet Aug 30, 2011
Could this be the rooftop collector we need for hydrogen, or is it going to be a huge device?


I am pretty sure you can make one to fit on the palm of your hand.. Just not going to get much hydrogen.
TrinityComplex
not rated yet Aug 30, 2011
I would be intereted to know what the conversion rate to surface area is for the substance, but so long as there is a sufficient storage apparatus it would be pretty shiny to just 'let it go' all day, every day. Even if it doesn't produce a huge amount, it's nearly free energy after a sufficient chunk of alloy is made.
dirk_bruere
5 / 5 (1) Aug 30, 2011
Efficiency? Numbers?
A Guy Named Mark
not rated yet Aug 30, 2011
Is there an anode / cathode parallel here? Or do you get both gasses released directly at the same point on the catalyst?
ED__269_
5 / 5 (1) Aug 30, 2011
Amazing and inspiring! would like to see numbers also!

I would also like to look at the math theory, follow that and how it improves as it changes due to improvements in production rates.

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Anode and cathode bases don't seem to fit to me. This seems to be about bond displacement at the point of energy absorption/excitation. i.e. seemingly; the chances of a minimal energy imput at the highest stress point of the H20 bond.
StarGazer2011
1.6 / 5 (7) Aug 30, 2011
Nice idea, but some numbers would be nice. $/m^3 , H/m^2, energy required for production. You know, some actual information and data rather than this dumbed down nonsense.

Also, since H2O vapor is a much more powerfull greenhouse gas than CO2 (according to alarmist theory) I reckon the greenies will eventually be against this too.
ED__269_
not rated yet Aug 30, 2011
H2O & CO2? you've got the wrong end of the stick!
ED__269_
1 / 5 (1) Aug 30, 2011
but to be fair- there is increased entropy. And that will add to Global Warming emission - even though this kind of a definition isn't one that is readily excepted.
Star_Gazer
2.6 / 5 (5) Aug 30, 2011
Also, since H2O vapor is a much more powerfull greenhouse gas than CO2 (according to alarmist theory) I reckon the greenies will eventually be against this too.


We should outlaw the oceans! Too much global warming from those darn things!
EyeNStein
1 / 5 (2) Aug 31, 2011
If it splits H2O into both gas components your home 'solar cell' could blow your house up.
Bonkers
3.7 / 5 (3) Aug 31, 2011
the energy to split H2O into H2 and O2 (G° = 1.23 eV) is essentially equal to the free energy change associated with photosynthesis [G° = 1.24 eV) therefore a good match for InP (bandgap = 1.29eV) and a good match for sunlight (trees work fine). Visible light is from 1.77eV for red, to 3eV for violet.
SteveL
5 / 5 (1) Aug 31, 2011
They likely use a ceramic absorbtion filter, much like in a nitrogen air compressor which blocks the O2 and other gasses and lets the nitrogen through. In this case you would block the oxygen and let the smaller hydrogen molecule pass to be stored or used.

This is good research and a significant advance in the usage of hydrogen for whatever purpose. It would be nice if we could cover our houses with a roof using a technology like this. As for the H2O "waste product" - it could easily be condensed into pure water and recycled back into the process.
SteveL
not rated yet Aug 31, 2011
Ugh, "nitogen compressor", not "nitrogen air compressor". If this web site wouldn't lock up on my posts sometimes I'd have caught and fixed that. I also haven't been able to rank articles for the last several weeks. Happily, I can still plop a "1" on folks like zuoma for their ads.
Ricochet
not rated yet Aug 31, 2011
the energy to split H2O into H2 and O2 (G° = 1.23 eV) is essentially equal to the free energy change associated with photosynthesis [G° = 1.24 eV) therefore a good match for InP (bandgap = 1.29eV) and a good match for sunlight (trees work fine). Visible light is from 1.77eV for red, to 3eV for violet.

I think what you're saying is that the trees don't blow up, so why should this?
TomSullivan
not rated yet Sep 13, 2011
Great job Team! As envisioned 4 years ago, there is a catalyst that is able to easily split water, and you have done it! Kudos to you! This could spring board our state into the next millennium in just a few short years!

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