High Throughput Screening of Complex Hydrides for Hydrogen Storage
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High Throughput Screening of Complex Hydrides for Hydrogen Storage Gregory J. Lewis, J.W. Adriaan Sachtler, John J. Low, David A. Lesch, Syed A. Faheem, Paul M. Dosek, Lisa M. Knight, and Craig M. Jensen1 UOP LLC, 50 E. Algonquin Rd., Des Plaines, IL 60017, U.S.A. 1 Hawaii Hydrogen Carriers LLC, 3540 Kumu Street, Honolulu HI 96822, U.S.A. ABSTRACT The discovery that dopants, such as Ti, cause NaAlH4 to reversibly desorb H2 at mild conditions has spurred a great deal of research into complex metal hydrides.1 However, no complex hydride meets the targets for automotive hydrogen storage. Our approach is to accelerate the rate of discovery of improved hydrides and dopants through the combination of Virtual High Throughput Screening (VHTS) and Combinatorial Synthesis and Screening (CSS). Our CSS methods will allow us to screen thousands of samples in a year. These samples will be prepared by ball milling mixtures of hydrides and dopants similar to the established method of preparing Ti doped NaAlH4. VHTS exploits a molecular mechanics method to screen a thousand phases in a month. The combination of combinatorial methods and VHTS will help us discover the most promising complex hydrides for hydrogen storage. We will show the results of our medium throughput CSS and VHTS as applied to the NaAlH4–LiAlH4 – Mg(AlH4)2 mixed alanate compositions. INTRODUCTION High Throughput Screening (HTS) is an approach to exploratory chemistry that has been embraced by many industries, including pharmaceuticals and industrial catalysis. The goal of HTS is to accelerate the rate of discovery in the exploratory setting, so that more time can be spent developing promising leads. In the laboratory, Combinatorial Synthesis and Screening (CSS) accomplish this via a combination of miniaturization, automation and parallelization of synthetic processes and diagnostic assays to identify possible leads. A complimentary approach which carries out the experiments more economically on the computer is Virtual High Throughput Screening (VHTS). VHTS uses NaAlH4, 5.6% theory to model the properties of interest to steer .1 laboratory work along the most promising lines of .9 .2 investigation. We are actively engaged in .8 .3 .7 applying both of these techniques to the discovery .4 .6 of new Hydrogen Storage Materials (HSM). The .5 .5 initial phase of our work involved setting up a .6 .4 medium throughput hydrogen capacity assay .7 .3 .8 which can analyze 8 samples in parallel. We .2 .9 .1 report here the application of this medium throughput assay and high throughput XRD to the .9 .8 .7 .6 .5 .4 .3 .2 .1 LiAlH4, 8.0% 2 * Mg(AlH4)2, 7.0% pursuit of new HSM’s in the NaAlH4 (1) –LiAlH4 (2) – Mg(AlH4)2 (3) mixed alanate system. While Figure 1. Compositions covered in the NaAlH4/2% Ti (1′) (5.6 wt. % H) is the state of NaAlH4 (1)- LiAlH4 (2)- Mg(AlH4)2 (3) the art, both 2 (8.0 wt. % H) and 3 (7.0 wt. % H), mixed system.
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EXPERIMENTAL DETAILS
4.5 4.5 4.0 4.0 3.5 3.5
Wt. % Hydrogen
while not reversible, offer higher hydrogen capacit
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