skip to main content

DOE PAGESDOE PAGES

Title: Anomalous H 2 Desorption Rate of NaAlH 4 Confined in Nitrogen-Doped Nanoporous Carbon Frameworks

Confining NaAlH 4 in nanoporous carbon scaffolds is known to alter the sorption kinetics and/or pathways of the characteristic bulk hydride reactions through interaction with the framework at the interface, increased specific surface area of the resulting nanoparticles, decreased hydrogen diffusion distances, and prevention of phase segregation. Although the nanosize effects have been well studied, the influence of the carbon scaffold surface chemistry remains unclear. Here we compare the hydrogen sorption characteristics of NaAlH 4 confined by melt infiltration in nitrogen-doped/undoped ordered nanoporous carbon of two different geometries. 23Na and 27Al MAS NMR, N 2 sorption, and PXRD verify NaAlH 4 was successfully confined and remains intact in the carbon nanopores after infiltration. Both the N-doped/undoped nanoconfined systems demonstrate improved reversibility in relation to the bulk hydride during hydrogen desorption/absorption cycling. Isothermal kinetic measurements indicate a lowering of the activation energy for H 2 desorption by as much as 70 kJ/mol in N-doped frameworks, far larger than the reduction in carbon-only frameworks. Most interestingly, this dramatic lowering of the activation energy is accompanied by an unexpected and anomalously low NaAlH 4 desorption rate in the N-doped frameworks. This suggests that the framework surface chemistry plays an important role in themore » desorption process and that the rate limiting step for desorption may be associated with interactions of the hydride and host surface. Our results indicate that functionalization of carbon scaffold surface chemistry with heteroatoms provides a powerful method of altering the characteristic hydrogen sorption properties of confined metal hydride systems. Furthermore, this technique may prove beneficial in the path to a viable metal hydride-based hydrogen storage system.« less
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [3] ;  [4] ;  [3] ;  [3] ;  [1]
  1. Univ. of Missouri - Saint Louis, Saint Louis, MO (United States)
  2. Washington Univ., St. Louis, MO (United States)
  3. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  4. Washington Univ., St. Louis, MO (United States); ABQMR Inc., Albuquerque, NM (United States)
Publication Date:
Report Number(s):
SAND-2018-4114J; SAND2019-3248J
Journal ID: ISSN 0897-4756; 666285
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 30; Journal Issue: 9; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Research Org:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1464194
Alternate Identifier(s):
OSTI ID: 1507405

Carr, Christopher L., Jayawardana, Waruni, Zou, Hongyang, White, James Lawrence, El Gabaly, Farid Marquez, Conradi, Mark S., Stavila, Vitalie, Allendorf, Mark D., and Majzoub, Eric H.. Anomalous H2 Desorption Rate of NaAlH4 Confined in Nitrogen-Doped Nanoporous Carbon Frameworks. United States: N. p., Web. doi:10.1021/acs.chemmater.8b00305.
Carr, Christopher L., Jayawardana, Waruni, Zou, Hongyang, White, James Lawrence, El Gabaly, Farid Marquez, Conradi, Mark S., Stavila, Vitalie, Allendorf, Mark D., & Majzoub, Eric H.. Anomalous H2 Desorption Rate of NaAlH4 Confined in Nitrogen-Doped Nanoporous Carbon Frameworks. United States. doi:10.1021/acs.chemmater.8b00305.
Carr, Christopher L., Jayawardana, Waruni, Zou, Hongyang, White, James Lawrence, El Gabaly, Farid Marquez, Conradi, Mark S., Stavila, Vitalie, Allendorf, Mark D., and Majzoub, Eric H.. 2018. "Anomalous H2 Desorption Rate of NaAlH4 Confined in Nitrogen-Doped Nanoporous Carbon Frameworks". United States. doi:10.1021/acs.chemmater.8b00305. https://www.osti.gov/servlets/purl/1464194.
@article{osti_1464194,
title = {Anomalous H2 Desorption Rate of NaAlH4 Confined in Nitrogen-Doped Nanoporous Carbon Frameworks},
author = {Carr, Christopher L. and Jayawardana, Waruni and Zou, Hongyang and White, James Lawrence and El Gabaly, Farid Marquez and Conradi, Mark S. and Stavila, Vitalie and Allendorf, Mark D. and Majzoub, Eric H.},
abstractNote = {Confining NaAlH4 in nanoporous carbon scaffolds is known to alter the sorption kinetics and/or pathways of the characteristic bulk hydride reactions through interaction with the framework at the interface, increased specific surface area of the resulting nanoparticles, decreased hydrogen diffusion distances, and prevention of phase segregation. Although the nanosize effects have been well studied, the influence of the carbon scaffold surface chemistry remains unclear. Here we compare the hydrogen sorption characteristics of NaAlH4 confined by melt infiltration in nitrogen-doped/undoped ordered nanoporous carbon of two different geometries. 23Na and 27Al MAS NMR, N2 sorption, and PXRD verify NaAlH4 was successfully confined and remains intact in the carbon nanopores after infiltration. Both the N-doped/undoped nanoconfined systems demonstrate improved reversibility in relation to the bulk hydride during hydrogen desorption/absorption cycling. Isothermal kinetic measurements indicate a lowering of the activation energy for H2 desorption by as much as 70 kJ/mol in N-doped frameworks, far larger than the reduction in carbon-only frameworks. Most interestingly, this dramatic lowering of the activation energy is accompanied by an unexpected and anomalously low NaAlH4 desorption rate in the N-doped frameworks. This suggests that the framework surface chemistry plays an important role in the desorption process and that the rate limiting step for desorption may be associated with interactions of the hydride and host surface. Our results indicate that functionalization of carbon scaffold surface chemistry with heteroatoms provides a powerful method of altering the characteristic hydrogen sorption properties of confined metal hydride systems. Furthermore, this technique may prove beneficial in the path to a viable metal hydride-based hydrogen storage system.},
doi = {10.1021/acs.chemmater.8b00305},
journal = {Chemistry of Materials},
number = 9,
volume = 30,
place = {United States},
year = {2018},
month = {4}
}