Trapping Sunlight for Later Use Requires Effective Catalysts
Article reviews work to imitate Mother Nature's processes
Hydrogen movement (white spheres) in metal catalyst. Animated picture provided by Jim Muckerman, Brookhaven National Laboratory.
Most people don't want to plan using their toaster or their computer based on when the sun shines. Solar cells only provide power when the weather cooperates. So, scientists at Pacific Northwest National Laboratory's Institute for Integrated Catalysis and elsewhere are working to use solar and wind energy to power reactions that turn water into hydrogen fuel that can be used when desired. The reverse reaction, in which H2 is turned into water, is an important reaction for hydrogen fuel cells.
Dr. Mary Rakowski DuBois and Dr. Dan DuBois of PNNL's IIC were invited by the journal of the French Academy of Sciences, Comptes Rendus Chimie, to review their work on metal catalysts that speed the conversion of water to hydrogen.
The cost of a catalyst: The problem is the best catalyst for this reaction is platinum, which sells for around $1000 an ounce. This cost is simply too high to permit mass production. However, Mother Nature performs the same water-splitting reactions in plants using enzymes with cheaper metals, nickel and iron. So, the authors focused on the same metals nature uses to promote these reactions.
Specifically, they focused on the proton relays in catalysts. The relays are clusters of atoms, which typically include nitrogen, that help deliver protons where they are needed for the reaction. That is, the relays move the protons to and from the metal at the center of the catalyst.
Researchers want to learn how this reaction is accomplished at the molecular and submolecular scales and then replicate and refine it for industry.
The future? Dan DuBois and PNNL scientist Dr. Morris Bullock have obtained funding from the U.S. Department of Energy's Office of Basic Energy Sciences to continue research into low-cost, effective catalysts to produce hydrogen fuel. In addition, they are working on more complex reactions involved in alternative fuel production.
Reference: DuBois MR and DL DuBois. 2008. "The role of pendant bases in molecular catalysts for H2 oxidation and production." Comptes Rendus Chimie 11(8):805-817.