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.