2000s
AFOSR: Turning Scientific Discovery into Air Force Opportunity
Artificial Photosynthesis (2009-2012) One AFOSR-funded program was included as a Time me magazine “Innovation of the Year” for 2011. The news media has paid a great deal of attention to Dr. Daniel Nocera's breakthrough research in artificial photosynthesis – and with good reason. 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. Solar energy could be a powerful solution to the energy needs of the future for both militaryy and commercial entities, but as Nocera points out, ut, power is needed all the time, not just when the sun is shining. Therefore, he and his research team at MIT investigated new methods to store solar energy. Nocera readily admits 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, 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, 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. Support from AFOSR enabled Nocera to conduct the basic research necessary to make this possible. Using cobalt-based oxide as a catalyst and phosphate as a proton acceptor, Nocera demonstrated a method for splitting water into oxygen molecules under environmentally friendly conditions. He then invented a nickel-based metal alloy to turn the remaining protons and electrons into hydrogen. These catalysts are then affixed to silicon as layers to produce the artificial leaf. In a presentation at AFOSR, Nocera expressed great pride in how easily this method can be prepared, saying that he often invites reporters and other interested parties into his lab to perform the experiment themselves. In the water-splitting experiment, the team places the leaf in a glass of phosphate-buffered water. When held up to sunlight, oxygen evolves from one side in a thin amorphous film containing the cobalt layer and 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 activ research is to have buildings serve as their own power stations. resea Given tthe ready availability of both cobalt-phosphate catalysts and solar-generated electricity, it would be possible to use any excess solar-ge electricity to split water into hydrogen and oxygen. These daytime e could be immediately stored and then recombined at night with products co fuel cells to power buildings as well as plug-in ground vehicles.101 po
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