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Improved H_2 Storage in Zeolitic Imidazolate Frameworks Using Li^+, Na^+, and K^+ Dopants, with an Emphasis on Delivery H_2 Uptake

Han, Sang Soo and Choi, Seung-Hoon and Goddard, William A., III (2011) Improved H_2 Storage in Zeolitic Imidazolate Frameworks Using Li^+, Na^+, and K^+ Dopants, with an Emphasis on Delivery H_2 Uptake. Journal of Physical Chemistry C, 115 (8). pp. 3507-3512. ISSN 1932-7447.

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We use grand canonical Monte Carlo simulations with first principles based force fields to show that alkali metal (Li^+, Na^+, and K^+)-doped zeolitic imidazolate frameworks (ZIFs) lead to significant improvement of H_2 uptake at room temperature. For example, at 298 K and 100 bar, Li-ZIF-70 totally binds to 3.08 wt % H_2, Na-ZIF-70 to 2.19 wt % H_2, and K-ZIF-70 to 1.62 wt % H_2, much higher than 0.74 wt % H_2 for pristine ZIF-70. Thus, the dopant effect follows the order of Li-ZIF > Na-ZIF > K-ZIF, which correlates with the H_2 binding energies to the dopants. Moreover, the total H_2 uptake is higher at lower temperatures: 243 K > 273 K > 298 K. On the other hand, delivery H_2 uptake, which is the difference between the total adsorption at the charging pressure (say 100 bar) and the discharging pressure (say 5 bar), is the important factor for practical on-board hydrogen storage in vehicles. We show that delivery H_2 uptake leads to Na-ZIF-70 (1.37 wt %) > K-ZIF-70 (1.25 wt %) > Li-ZIF-70 (1.07 wt %) > ZIF-70 (0.68 wt %), which is different from the trend from the total and excess uptake. Moreover, the delivery uptake increases with increasing temperatures (i.e., 298 K > 273 K > 243 K)! To achieve high delivery H_2 uptake at room temperature, the large free volume of ZIFs is required. We find that higher H_2 binding energy needs not always lead to higher delivery H_2 uptake.

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Goddard, William A., III0000-0003-0097-5716
Additional Information:© 2011 American Chemical Society. Received: January 12, 2011. Article ASAP February 09, 2011. Published In Issue March 03, 2011. This research was performed for the Hydrogen Energy R&D Center, one of the 21st Century Frontier R&D programs, funded by the Ministry of Education, Science and Technology of Korea. WAG is supported by the WCU program (31-2008-000-10055-0) through the National Research Foundation of Korea. We thank Accelrys Korea for providing modeling software.
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Ministry of Education, Science and Technology of KoreaUNSPECIFIED
National Research Foundation of Korea WCU Program31-2008-000-10055-0
Issue or Number:8
Record Number:CaltechAUTHORS:20110321-102838744
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Official Citation:Improved H2 Storage in Zeolitic Imidazolate Frameworks Using Li+, Na+, and K+ Dopants, with an Emphasis on Delivery H2 Uptake Sang Soo Han, Seung-Hoon Choi, William A. Goddard III The Journal of Physical Chemistry C 2011 115 (8), 3507-3512
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23010
Deposited By: Tony Diaz
Deposited On:21 Mar 2011 20:23
Last Modified:26 Nov 2019 11:15

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