Oct 10 2008
Solar energy could be a powerful solution to the energy needs of the future for military and commercial entities.
However, scientists point out the constant need for power, not just when the sun is shining.
Funding support from the Air Force Office of Scientific Research is enabling a Massachusetts Institute of Technology team led by Dr. Daniel Nocera to investigate new methods to store solar energy.
Dr. Nocera is known for his breakthrough research in artificial photosynthesis. This technology has the potential to power an entire building for one day using only a few gallons of water and light energy from the sun.
Dr. Nocera is the first to admit that this is not a new concept, but the key to his research has been finding a technique that is cheap, efficient and easy to manufacture.
After ruling out several lower energy options, Dr. Nocera's team chose to pursue photosynthesis, which naturally stores energy when splitting the bonds of water to produce oxygen and nature's chemical equivalent of hydrogen, or NADPH. Using this model, he sought to develop an artificial photosynthesis that split water molecules into oxygen and molecular hydrogen (rather than NADPH) without the costs and harsh conditions that accompany existing commercial electrolyzers.
Using cobalt as a catalyst and phosphate as a proton acceptor, Dr. Nocera is able to demonstrate a method for splitting water into hydrogen and oxygen molecules under environmentally friendly conditions.
In the water-splitting experiment, the team places an electrode in phosphate-buffered water containing cobalt. When they apply electricity, oxygen evolves from one side in a thin amorphous film containing phosphate and cobalt while hydrogen evolves simultaneously from the other side.
Because the catalytic film forms in situ, or in the reaction mixture, a self-repair mechanism is implied. In this case, meaning that as oxygen evolves, cobalt is thought to cycle through different oxidation states as it attaches to phosphate and then to the electrode. The results indicate that any cobalt that falls off the electrode appears to reattach to another phosphate, activating it for another catalytic cycle.
The ultimate goal of this research is to have buildings serve as their own power stations. Given the ready availability of both cobalt-phosphate catalysts and solar-generated electricity, it would be possible to use any excess daytime electricity to split water into hydrogen and oxygen. These products could be immediately stored and then recombined at night with fuel cells to power buildings as well as plug-in ground vehicles.