SCIENCE & TECHNOLOGY FUEL FOR THOUGHT Buchanan (from left), Dresselhaus, and Crabtree.
MOVING TOWARD A HYDROGEN ECONOMY DOE workshop brings together scientists to prioritize research needs for switching to hydrogen MITCH JAC0BYP C&EN CHICAGO
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for a hydrogen research initiative, the Bush Administration seeks to make the U.S. "much less dependent on foreign sources of oil" and to improve air quality, as indicated by the President inJanuary in his State ofthe Union address.The fundingproposal received immediate support from scientists and some members of Congress. But now the Department of Energy must prioritize the research requirements needed to meet the goals set forth in the President's proposal—goals such as putting hydrogen-powered automobiles on showroom floors by the end of the next decade. To aid in its task, DOE's Office of Basic Energy Sciences (BES) convened a twoand-a-half-day workshop last month in Rockville, Md., in which a panel of distinguished scientists and engineers discussed and debated a host of issues related to developing a "hydrogen economy "The term refers to an energy system based on hydrogen as the principal energy medium.
The workshop drew roughly 150 attendees. It was chaired by Mildred S. Dresselhaus, a professor of physics and electrical engineering at Massachusetts Institute ofTechnology, and cochaired by Argonne National Laboratory's George W Crabtree and Michelle Buchanan of Oak Ridge National Laboratory Patricia M. Dehmer, BES associate director of science, laid out the intended goals of the workshop as the meeting began. "'We'd like you to identify the fundamental research needs and opportunities in hydrogen production, storage, and usage," she said. Attendees were asked to focus on "new, emerging, and scientifically challenging areas that have the potential to have significant impact in science and technologies." Dehmer charged the scientific panel with articulating the requirements needed to overcome short-term "showstoppers"—problems that must be solved soon if progress is to be made—and to address long-term "grand challenges." Based on DOE's assignment, the work-
shop was divided into three breakout sessions: one focusing on production of hydrogen, one on storage and distribution of the gas, and one session covering fuel cells and novel fuel-cell materials. But before splitting up into discussion groups, a small number of speakers presented overviews of select topics. In one plenary presentation, Steven G. Chalk, a manager for DOE's program in hydrogen, fuel cells, and infrastructure technologies, explained that the driver for the Bush Administration's hydrogen-fuel initiative is the need for energy security "Right now, the U.S. is importing 55% of its oil—and under the status quo, that number is expected to grow to 68% by 2025," Chalk asserted. Feedstock flexibility is one feature that makes hydrogen a promising energy source, Chalk commented. Hydrogen can be produced from biomass and by splitting water using renewable electrical resources, such as wind and solar energy The fuel can also be produced from oil, natural gas, and other fossil sources. The diversity enables manufacturers to switch from one source to another in case of feedstock shortages or price jumps. "The idea is not to have to rely on a single source for hydrogen as an energy carrier," Chalk stated. He underscored the point by noting that the U.S. currently derives 97% of its energy for transportation needs from oil. A DETAILED OVERVIEW of hydrogenstorage science and technology was presented by George J. Thomas, a hydrogen consultant and retired Sandia National Laboratories researcher. Thomas reviewed methods for storing gaseous and liquid hydrogen and discussed studies in which hydrides, carbon materials, porous compounds, and other solids were used for storing hydrogen. Framing the hydrogen-economy discussion in a historical context, Thomas drew parallels between the state of transportation today and that of 100 years ago. He noted that in the early 1900s, a revolutionary vehicle—the automobile—was introduced. Its internal combustion engine and the gasoline fuel that powered it were novel. The vehicle's driving range was limited initially, and a fuel production and
'Theory can play an important role in these areas, provided we know what questions to ask." HTTP://WWW.CEN-ONLINE.ORG
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SCIENCE & TECHNOLOGY distribution infrastructure had to be developed to support it. 'Ahundred years later we're talking about the same things/'Thomas said. Hydrogenpowered fuel-cell vehicles with electric drive-train motors are novel today. And their success in the marketplace depends on
technology is either too expensive or too inefficient for very large-scale use, Mallouk reported. The production group identified several priorityresearch areas, including developing inexpensive catalysts and understanding fundamental processes in biological hydrogen
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many of the same types of infrastructure advances that were needed a century ago, he remarked. "Hydrogen storage is a key enabling technology" Thomas argued, because it plays a major role in production, distribution, and utilization of the fuel. For the better part of two days, the scientists held breakout sessions in which experts led detailed and lively discussions on various topics connected to the production, storage, and usage of hydrogen. For example, in the production session, Allen J. Bard, a University ofTexas, Austin, chemistry professor, led the discussion on solar production methods, and Jennifer S. Holmgren, a research director at UOP, Des Plaines, 111., guided a fossil-fuel discussion. Following the topical discussions, the session chairs presented their group's findings to the workshop attendees. Pennsylvania State University chemistry professor Thomas E. Mallouk, one of the hydrogen-production session chairs, emphasized that several methods for making hydrogen from sources other than fossil fuels already exist, yet none is economical at the present time. And fossil-fuel-based production—today's principal source—is not sustainable, he added. Regarding solar-based technologies, Mallouk noted that complete systems are available today, including photovoltaic units that generate electricity from sunlight, coupled with electrolyzers that split water into hydrogen and oxygen. Also, newer technologies, such as semiconductor-based photoelectrochemical cells, dyesensitized T i 0 2 solar cells, and all-organic thin-film cells, can be used to produce hydrogen from water. But in each case, the 36
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Mallouk production. The group also proposed focusing on the components of "solar paint," a thin-film material that could enable photovoltaic sources to function inexpensively and efficiently Mallouk suggested that perhaps the inexpensive reel-to-reel production methods used to make photographic film might be adapted to solar cells. Toward that end, the group included investigations ofphotoinduced electron-transfer processes at interfaces as a research priority Kathleen C. Taylor, a retired research director with General Motors and one of the chairs of the hydrogenstorage group, reported that "radically different" materials are needed for storing hydrogen because presently no materials come close to meeting long-term government storage capacity targets. But she cautioned that researchers shouldn't focus Taylor so tightly on storage media that they ignore the related issues of containment and transport. IN THE AREA of metal hydrides, the storage group concluded that additional research is needed to understand degradation processes and the roles played by dopants and catalysts in improving kinetics for better low-temperature performance. Taylor singled out complex hydrides as a priority research area, suggesting that an intensive interdisciplinary research program be developed to study promising materials such as Ti-doped LiAlH 4 , NaBH 4 ,
and related compounds. She added that researchers should also focus on developing computational methods for predicting materials' properties and trends and that nanoscale design techniques should be exploited for preparing new hydrogen-storage materials. The team focusing on fuel cells also put together a list of key scientific problems and research priorities. Thomas A. Zawodzinskijr., professor of chemical engineering at Case Western Reserve University, reported on some of the topics discussed by that group. For example, he noted that fuel cells using membranes that conduct protons efficiently above 100 °C offer benefits in terms of their ability to manage heat and withstand CO poisoning. But developing satisfactory high-temperature proton conductors has been difficult thus far. Zawodzinski also pointed out that fuel-cell research would greatly benefit from reliable, simple, and straightforward methods for characterizing membranes outside of fuel cells. Among other topics listed as fuel-cell research priorities were understanding basic materials-degradation mechanisms and developing functionalized materials with nanostructures tailored to meet fuel-cell needs. Zawodzinski added that "theory can play an important role in these areas, pro-
Zawodzinski vided we know what questions to ask." Dresselhaus warned the workshop attendees during the opening session about the difficulties in making the transition to hydrogen fuel. "If we're going to make progress, we'll need new ideas in several areas and very close collaboration between science and technology," she said. By the time the workshop ended, the session chairs had pieced together a rough outline of a report for the organizing committee. Dresselhaus noted that the organizers, in turn, expect to present a final report to D O E by the end of the month. • HTTP://WWW.CEN-ONLINE.ORG
