Critical elements—and especially rare earths—were in the news in 2011, as a sample of headlines demonstrates:
- “Stable rare earth supply sought,” Daily Yomiuri Online, September 8.
- “Chasing rare earths, foreign companies expand in China,” New York Times, August 24.
- “China to reform rare earth exports after WTO,” Reuters, July 6.
- “China holds the world hostage in rare earth metals,” Business Insider, June 13.
- “Got Yttrium?” Time, March 28.
- “Can Toyota innovate its way out of the Prius’s rare earth element problem?” Christian Science Monitor, January 19.1
Widespread concern over the future availability of critical elements led the Chemical Sciences Roundtable to hold a workshop on September 29-30, 2011, in Washington, D.C., on the role of the chemical sciences in finding alternatives to critical resources. Key topics addressed during the workshop included
- The economic and political matrix for addressing the issue,
- The history of societal responses to key mineral and material shortages,
- The applications for and properties of existing minerals and materials, and
- The chemistry of possible replacements.
“The chemical sciences have not yet been much involved in the national discussion over critical elements,” said Patricia Thiel, Division Director for Science and Technology at Ames Laboratory, Distinguished Professor of Chemistry at Iowa State University, and one of three members of the organizing committee for the workshop. Yet historically the chemical sciences have played an essential role in this area. In the early years of the 20th century, fertilizer was so scarce that it was sometimes stolen, and war broke out in South America over one of the world’s two main sources of nitrogen, guano from bird droppings (the other main source at the time was sodium nitrate mined in Chile). Then, in 1909, Fritz Haber discovered a way to fix atmospheric nitrogen as ammonia using iron as a catalyst at high pressure, and a few years later Carl Bosch, an industrial chemist at BASF, developed a way to apply this process on an industrial scale. The Haber-Bosch process was born in controversy, since it prolonged Germany’s ability to wage World War I without blockaded imports from South America. But the discovery has had “great impact that continues to reverberate today,” said Thiel. Most significantly, by facilitating intensive agriculture, it enabled the great and continued expansion of the human population in the 20th and 21st centuries.
The same year that Fritz Haber fixed nitrogen using the precursor to the modern process, chemists produced the first totally synthetic rubber. When the price of natural rubber, which was produced primarily in Asia, increased sharply in 1925, industrial production of synthetic rubber rose substantially. “But the real stimulant to industrial production came in World War II,” said Thiel, “when the Axis countries took over the supply fields in Asia and cut off all supplies of natural rubber to the Allies.”
In modern times, critical materials are used in many everyday activities. Essentially all electronic devices use a wide variety of these materials, including rare earth elements,
1Roderick Eggert, one of the three members of the workshop organizing committee, listed these headlines in his presentation summarized in Chapter 2.
precious metals, and other rare, expensive elements of the periodic table. For example, the Toyota Prius uses at least eight different critical elements in its design. As described in Chapter 2, in everything from the hybrid electric motor, to the LCD screen in the passenger compartment, to the rechargeable NiMH battery to power the car, to the catalytic converter that cleans the exhaust, critical elements play a primary role in the operation of this modern car.
Those examples “nicely illustrate the role of chemistry in addressing shortages of critical materials,” Thiel concluded, “and the chemical sciences continue to have an enormous role to play today.”
After Thiel’s introductory remarks, the workshop consisted of five pairs of related presentations and subsequent discussions. These presentations are summarized briefly below and in Chapters 2-6 of this summary.
Chapter 2: Assessments of Criticality
Roderick Eggert, Professor and Director of the Division of Economics and Business at the Colorado School of Mines, presented a framework for assessing the availability of critical elements that was developed by a National Research Council committee that recently examined the issue (NRC, 2008). Elements can be positioned in a two-dimensional array comparing their importance in use and supply risk. Using this framework, the most critical elements are the platinum-group elements, the rare earths, manganese, indium, and niobium. Eggert elaborated on his view that the chemical sciences are essential in finding substitutes for critical elements, enhancing mineral extraction and recovery processes, improving manufacturing efficiency, and enabling better recycling.
Diana Bauer, Director of the Office of Economic Analysis in the Department of Energy’s Office of Policy and International Affairs, presented the main findings of the Critical Material Strategy released by the Department of Energy (DOE) in 2010. The report found that “four clean energy technologies—wind turbines, electric vehicles, photovoltaic cells, and fluorescent lighting—use materials that are at risk of supply disruptions in the short term. In the report, five rare earth elements (dysprosium, neodymium, terbium, europium, and yttrium), as well as indium, were assessed as most critical in the short term” (DOE, 2010).
Chapter 3: Critical Materials in Catalysis
James Stevens, Corporate Fellow, Core Research and Development Department, Dow Chemical Company, gave a broad perspective on the use of critical materials, especially platinum-group metals, as catalysts in industry. Various aspects of the catalysis process are more economically significant than the cost of the metals, and many chemical processes have evolved from originally using low-cost metals such as cobalt to much scarcer metals because the high cost of separations and capital expenses overwhelm the difference in the price of the metal. Opportunities exist for further work in the areas of emissions catalysis, hydrosilylation, hydroformylation, and enantioselective catalysis to help address this cost differential.
Jingguang Chen, Claire D. LeClaire Professor of Chemical Engineering and Co-Director of the Energy Frontier Research Center, University of Delaware, presented his research results aimed at reducing and replacing platinum in catalysis. In water electrolysis, for example, monolayer platinum can achieve the same activity as bulk platinum using vastly less precious material. In biomass conversion reactions, a nickel on tungsten carbide catalyst can replace a platinum nickel catalyst for the production of hydrogen. These platinum-free catalysts also are very active in the direct conversion of cellulose from plants to useful chemicals that can be used in our current chemical plan infrastructure.
Chapter 4: Replacing Critical Materials with Abundant Materials
Morris Bullock, Laboratory Fellow and Director of the Center for Molecular Electrocatalysis at the Pacific Northwest National Laboratory, described the development of electrocatalysts based on inexpensive, Earth-abundant metals. Low-temperature fuel cells generally use platinum, but nickel complexes can effectively catalyze the oxidation of hydrogen. Related complexes of cobalt, iron, and manganese are being studied as well, showing that it is possible to rationally design catalysts based on abundant, inexpensive metals as alternatives to the more expensive precious metals.
Christine Lambert, Technical Leader, Ford Research and Advanced Engineering, recounted the 30-year history of using base metals to replace precious metals in three-way automobile catalysts that simultaneously control hydrocarbons, carbon monoxide, and nitrogen emissions in gasoline vehicle exhaust. There is no known combination of base metals that are as active and durable as precious metals. But there has been a general reduction of precious metals use due to the addition of stabilizers to improve catalyst effectiveness over longer mileages, reduction of poisons present in the fuel and oil, and tighter control of engine parameters. Current diesel aftertreatment technologies, which do not use precious metals, also have been undergoing rapid evolution with the development of catalysts that have improved thermal stability and wider operating windows for temperatures and flow rates.
Chapter 5: Optoelectronics and Photovoltaics
Joseph Shinar, Senior Physicist at the Ames Laboratory, Professor and Chair of the Department of Physics and Astronomy, and Professor of Electrical and Computer Engineering at Iowa State University, discussed five critical materials or families of materials in optoelectronic technologies: erbium-doped fiber amplifiers, which are critical components of the repeaters in optical fiber networks; solid-state lasers based on lanthanide dopants in yttrium aluminum garnet, which are used extensively in spectroscopy and laser lithotripsy; indium in various ubiquitous III-V devices; transparent conducting indium tin oxide films, which are currently behind virtually 100 percent of all displays and figure similarly in the emerging organic light-emitting diode (OLED)-based solid-state lighting paradigm; and heavy rare earth elements which are currently critical for efficient OLED-based displays. He described examples highlighting the importance, availability, and estimated amounts of these metals that will be needed as these technologies mature and pervade the world economy in the coming decades.
Ken Zweibel, Director of the George Washington University Solar Institute, discussed the rapidly dropping cost and increasing use of photovoltaic (PV) solar cells and prospects for further expansion of these materials. The most important materials that are needed to produce solar power today include silicon, silver, tellurium, and cadmium. Emerging technologies could require significant quantities of indium, selenium, molybdenum, gallium, germanium, arsenic, and ruthenium. Some of these materials have supply or cost issues, which has spurred interest in developing strategies to reduce the amounts of materials needed to effectively produce electricity. New sources and additional refining capacity will be essential if demand for these materials greatly increases.
Chapter 6: Critical Materials in Large-Scale Battery Applications
David Bradwell, Chief Technology Officer at Liquid Metal Battery Corporation and Visiting Scientist at the Massachusetts Institute of Technology, explained that batteries designed for grid-scale energy storage applications face a unique set of material selection challenges. Whereas many other power technologies can improve performance via enhanced material microstructure or device design optimization, the energy capacity of a battery is directly related to the amount of active material. For broad-scale energy-intensive applications, this means the active materials must be inherently low cost and sufficiently abundant. Interestingly, the cost of the raw active materials is not always the primary cost driver; thus, to more fully evaluate the opportunity for emerging storage technologies, the entire system must be considered. A host of new battery technologies—including a set of liquid metal battery projects—are being pursued at universities, startup companies, and large well-established corporations across the country.
Jay Whitacre, Chief Technology Officer of Aquion and Professor of Engineering and Public Policy at Carnegie Mellon University, looked at battery technologies for energy applications, including lithium-ion and aqueous electrolyte batteries. The adoption of lithium-ion battery technology is, as of this workshop, not constrained by materials. Rather, it is constrained by the way the materials function and the complexity of the device itself. In contrast, low-cost, low-energy-density, and long-lifetime batteries could serve as a feasible and economic means of energy storage.
Chapter 7: General Observations
The final chapter compiles some general observations made by the individual workshop speakers that apply broadly to critical materials and the role of the chemical sciences in addressing these issues.
This page intentionally left blank.