Published on Tuesday, 14 February 2012 18:31
By Katrice R. Jalbuena
While any photosynthetic organism contains PSI, the researchers chose to work with algae.
Molecular structures extracted from plants could become the key both for making electrons out of sunlight and hydrogen for fuel cells, a concept that's continuously being explored by scientists.
In an interview, biochemist Barry D. Bruce of the University of Tennessee, Knoxville told EcoSeed that a key protein complex (or photosystem) in photosynthesis known as photosystem-I or PSI can be extracted and integrated in devices that either convert light into electricity or that produce hydrogen fuel when exposed to sunlight.
If it works out well, these kinds of devices can satisfy low-power energy needs such as small electronics, or can be sources of low-cost power for developing countries.
Converting light to power
Mr. Bruce is a professor of biochemistry and molecular biology at the University of Tennessee. He is a leading faculty at the university's Bredesen Center for Interdisciplinary Research and Graduate Education, a joint UT-Oak Ridge National Laboratory academic unit.
With colleagues from the Massachusetts Institute of Technology and the 'Ecole Polytechnique F'ed'erale de Lausanne in Switzerland, he recently released a paper describing their work with PSI.
"We take out the components that are the basis for photosynthesis," Mr. Bruce explained to EcoSeed
. "Then we integrate them - through a relatively simple step - into an inorganic semiconductor known as titanium oxide."
Mr. Bruce said they bioengineer the PSI complex to self-assemble and bond with the titanium oxide semiconductor material in a relatively simple process.
While any photosynthetic organism contains PSI, the researchers chose to work with blue-green algae because it's easier to work with and is also thermophilic, or capable of living in and withstanding very high temperatures.
According to Mr. Bruce, the PSI preserves its biological activity and, when exposed to photons of light, they generate and transfer electrons into the semiconductor material and produce electricity.
Although many other researchers have used photosystems for solar power generation (see EcoSeed
), this is the first time scientists used titanium.
Though the current technology only has an efficiency of about .08 percent, or almost one in a thousand photons getting converted into electrons, Mr. Bruce is confident that this can be improved to the point that devices using PSI could be a relatively low-cost alternative to current solar energy generating technology.
"We've proven that we can do it better and easier. Easier is one of the more important things," said Mr. Bruce.
"The idea is, if you're ever going to make things cheap, it has to be easy," he explained. "I think the fact that the technology is capable of self-assembly is a really good breakthrough."
But this is not the first time Mr. Bruce worked with PSI in chemical systems to revolutionize alternative energy sources. In 2009, he led a team of researchers from UT Knoxville and the Oak Ridge National Laboratory to use PSI as part of a catalyst for the production of hydrogen fuel.
Much like how they now combine PSI with titanium oxide, Mr. Bruce and his colleagues coupled PSI with a platinum catalyst to produce a steady supply of hydrogen when it is exposed to light.
"We demonstrated a very robust, self-organized nanoparticle that - if you shine light on it - makes hydrogen," said Mr. Bruce.
According to Mr. Bruce, not only was the nanoparticle robust and easy to assemble, it also demonstrated an ability to keep producing hydrogen over a long period of time.
"We worked with it for over three months, and it kept making hydrogen all that time," he said.
Photosystems have actually been used previously to produce hydrogen, the point being to mimic plant photosynthesis to produce the needed resource. (See a related EcoSeed
). The problem has been the huge cost of platinum.
But currently, for both hydrogen production and solar energy production, another goal is to increase the amount of fuel and energy that can be generated by the systems.
"We're trying to make it where we can absorb more solar radiation. Right now, we only take in a small portion of the sun's light - that which the plants absorb - but maybe we can expand that to absorb more wavelengths of light," said Mr. Bruce.