Princeton ACS Section Dinner Meeting
Monday, November 19, 2012
our
guest speaker will be
Professor Charles Dismukes
Department of Chemistry and Chemical Biology, Rutgers University, Piscataway NJ
Location: |
Frick Laboratory, Princeton University |
Social mixer: |
5:30 pm in CaFe, Taylor Commons |
Presentation: |
6:30 pm in Taylor Auditorium |
Dinner: |
Immediately following presentation in CaFe |
"Solar Fuels from Artificial Photosynthesis: How Biology has Informed Materials Science"
Abstract
Future human populations cannot survive on Earth without developing renewable energy. Hydrogen is the source of all
practical fuels, whether as H2 gas or hydrocarbons, and water is its only globally available renewable feedstock. Three
limitations to storing solar energy as hydrogen-derived fuels from water are: 1) need to replace noble metals as
catalysts to split water into its elements; 2) lowering both the intrinsic electrochemical inefficiencies for conversion
(catalyst over-potentials) and the extrinsic inefficiencies for matching the electrical source to the reactions
(transformers), and 3) design of low cost "disposable" electrolyzers and solar cells. I will discuss new solutions to items
1 and 2 emerging from R&D.
Nature has already solved problem (1) for solar-to-fuel energy conversion in oxygenic phototrophs. However, materials
scientists working on catalysts are largely unaware of nature's principles. These organisms all use a cubical
calcium/manganese-oxo cluster to split water, MnO[Mn3CaO4]. After summarizing the principles used by natural
photosynthetic organisms to oxidize water, I shall illustrate five examples of structurally well-characterized, bioinspired,
materials that we have made, that illustrate these principles. Organometallic metal-oxo cubanes, containing Mn4O4-
and Co4O4- cores surrounded by organic ligands as templating scaffold, share structural homology to the
photosynthetic catalytic site and were among the first catalysts emulating nature's winning design. Elimination of the
unstable organic scaffolding is absolutely essential for practical catalysts for water splitting. This need led us to search
for inorganic materials that could be found naturally or tailored synthetically to adopt the bionspired blueprint found in
photosynthesis, while exhibiting the appropriate redox chemical properties. To test the importance of the bioinspired
cubical structure, we synthesized 8 of the 30 predicted structurally distinct polymorphs of manganese and oxygen,
MnxOy. This revealed that, like the photosynthetic core, only those polymorphs possessing cubical Mn4O4 building
blocks and long (weak) Mn-O bonds are catalysts for water oxidation. The structural advantage of the bioinspired
cubical topology for catalysis of water oxidation is clearly illustrated by members of the binary spinels, compositionally
AB2O4. For example, I will illustrate water oxidation activity of two distinct structural polymorphs of LiCoO2. The cubic
"spinel" polymorph is ~100 times more active than the thermodynamically more stable "layered" polymorph, commonly
used in batteries. Comparison of this material as electro-catalyst in alkaline electrolyzers reveals it equals or outperform
iridium and platinum catalysts in independent tests. This material is licensed for development and may prove a suitable
substitute in future commercial electrolyzers.
Biography
Professor G. Charles Dismukes is Professor of Chemistry and Chemical Biology at Rutgers University, and a member
of the Waksman Institute and the Biochemistry and Microbiology Departments. His research interests focus on
biological and chemical methods for renewable solar-based fuel production, photosynthesis, metals in biological
systems and tools for investigating these systems. His published works describe the biology and chemistry of oxygen
production in natural photosynthetic systems, the synthesis and characterization of bioinspired catalysts for renewable
energy production, and the use of microorganisms as cell factories for the production of bio-fuels from renewable
sources. Chuck earned his BS in chemistry, with high honors, from Lowell Technological Institute, in Lowell,
Massachusetts, and his PhD in chemistry from the University of Wisconsin, Madison. After a postdoctoral appointment
at the University of California-Berkeley, Chuck joined the faculty of the chemistry department at Princeton University in
Announcement of the Princeton ACS Section1978. He rose through the ranks to appointment as full Professor of chemistry in 1991. In 2010, Professor Dismukes
transferred to Emeritus status at Princeton, and was lured to our northern neighbor, where he continues his research
on photosynthesis and renewable solar-based fuel production as a member of the Rutgers faculty.
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