skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Capacity enhancement of aqueous borohydride fuels for hydrogen storage in liquids

Abstract

In this work we demonstrate enhanced hydrogen storage capacities through increased solubility of sodium borate product species in aqueous media achieved by adjusting the sodium (NaOH) to boron (B(OH)3) ratio, i.e., M/B, to obtain a distribution of polyborate anions. For a 1:1 mole ratio of NaOH to B(OH)3, M/B = 1, the ratio of the hydrolysis product formed from NaBH4 hydrolysis, the sole borate species formed and observed by 11B NMR is sodium metaborate, NaB(OH)4. When the ratio is 1:3 NaOH to B(OH)3, M/B = 0.33, a mixture of borate anions is formed and observed as a broad peak in the 11B NMR spectrum. The complex polyborate mixture yields a metastable solution that is difficult to crystallize. Given the enhanced solubility of the polyborate mixture formed when M/B = 0.33 it should follow that the hydrolysis of sodium octahydrotriborate, NaB3H8, can provide a greater storage capacity of hydrogen for fuel cell applications compared to sodium borohydride while maintaining a single phase. Accordingly, the hydrolysis of a 23 wt% NaB3H8 solution in water yields a solution having the same complex polyborate mixture as formed by mixing a 1:3 molar ratio of NaOH and B(OH)3 and releases >8 eq of H2. Bymore » optimizing the M/B ratio a complex mixture of soluble products, including B3O3(OH)52-, B4O5(OH)42-, B3O3(OH)4-, B5O6(OH)4- and B(OH)3, can be maintained as a single liquid phase throughout the hydrogen release process. Consequently, hydrolysis of NaB3H8 can provide a 40% increase in H2 storage density compared to the hydrolysis of NaBH4 given the decreased solubility of sodium metaborate. The authors would like to thank Jim Sisco and Paul Osenar of Protonex Inc. for useful discussion regarding liquid hydrogen storage materials for portable power applications and the U.S. DoE Office of Energy Efficiency and Renewable Energy Fuel Cell Technologies Office for their continued interest in liquid hydrogen storage carriers. Pacific Northwest National Laboratory is a multi-program national laboratory operated for DOE by Battelle. The authors dedicate the work to the memory of Professor Sheldon Shore. His contributions to boron hydride chemistry set the foundation for many who have followed.« less

Authors:
 [1];  [1];  [2];  [2];  [2];  [3];  [2]
  1. U.S. Borax Inc., Rio Tinto, CO (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Univ. of Wollongong, NSW (Australia)
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1225147
Report Number(s):
PNNL-SA-105083
Journal ID: ISSN 0925-8388; HT0202000
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Alloys and Compounds
Additional Journal Information:
Journal Volume: 645; Journal Issue: S1; Journal ID: ISSN 0925-8388
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; liquid hydrogen storage; solubility; polyborate mixtures.

Citation Formats

Schubert, David, Neiner, Doinita, Bowden, Mark, Whittemore, Sean, Holladay, Jamie, Huang, Zhenguo, and Autrey, Tom. Capacity enhancement of aqueous borohydride fuels for hydrogen storage in liquids. United States: N. p., 2015. Web. doi:10.1016/j.jallcom.2015.01.063.
Schubert, David, Neiner, Doinita, Bowden, Mark, Whittemore, Sean, Holladay, Jamie, Huang, Zhenguo, & Autrey, Tom. Capacity enhancement of aqueous borohydride fuels for hydrogen storage in liquids. United States. https://doi.org/10.1016/j.jallcom.2015.01.063
Schubert, David, Neiner, Doinita, Bowden, Mark, Whittemore, Sean, Holladay, Jamie, Huang, Zhenguo, and Autrey, Tom. 2015. "Capacity enhancement of aqueous borohydride fuels for hydrogen storage in liquids". United States. https://doi.org/10.1016/j.jallcom.2015.01.063.
@article{osti_1225147,
title = {Capacity enhancement of aqueous borohydride fuels for hydrogen storage in liquids},
author = {Schubert, David and Neiner, Doinita and Bowden, Mark and Whittemore, Sean and Holladay, Jamie and Huang, Zhenguo and Autrey, Tom},
abstractNote = {In this work we demonstrate enhanced hydrogen storage capacities through increased solubility of sodium borate product species in aqueous media achieved by adjusting the sodium (NaOH) to boron (B(OH)3) ratio, i.e., M/B, to obtain a distribution of polyborate anions. For a 1:1 mole ratio of NaOH to B(OH)3, M/B = 1, the ratio of the hydrolysis product formed from NaBH4 hydrolysis, the sole borate species formed and observed by 11B NMR is sodium metaborate, NaB(OH)4. When the ratio is 1:3 NaOH to B(OH)3, M/B = 0.33, a mixture of borate anions is formed and observed as a broad peak in the 11B NMR spectrum. The complex polyborate mixture yields a metastable solution that is difficult to crystallize. Given the enhanced solubility of the polyborate mixture formed when M/B = 0.33 it should follow that the hydrolysis of sodium octahydrotriborate, NaB3H8, can provide a greater storage capacity of hydrogen for fuel cell applications compared to sodium borohydride while maintaining a single phase. Accordingly, the hydrolysis of a 23 wt% NaB3H8 solution in water yields a solution having the same complex polyborate mixture as formed by mixing a 1:3 molar ratio of NaOH and B(OH)3 and releases >8 eq of H2. By optimizing the M/B ratio a complex mixture of soluble products, including B3O3(OH)52-, B4O5(OH)42-, B3O3(OH)4-, B5O6(OH)4- and B(OH)3, can be maintained as a single liquid phase throughout the hydrogen release process. Consequently, hydrolysis of NaB3H8 can provide a 40% increase in H2 storage density compared to the hydrolysis of NaBH4 given the decreased solubility of sodium metaborate. The authors would like to thank Jim Sisco and Paul Osenar of Protonex Inc. for useful discussion regarding liquid hydrogen storage materials for portable power applications and the U.S. DoE Office of Energy Efficiency and Renewable Energy Fuel Cell Technologies Office for their continued interest in liquid hydrogen storage carriers. Pacific Northwest National Laboratory is a multi-program national laboratory operated for DOE by Battelle. The authors dedicate the work to the memory of Professor Sheldon Shore. His contributions to boron hydride chemistry set the foundation for many who have followed.},
doi = {10.1016/j.jallcom.2015.01.063},
url = {https://www.osti.gov/biblio/1225147}, journal = {Journal of Alloys and Compounds},
issn = {0925-8388},
number = S1,
volume = 645,
place = {United States},
year = {Thu Oct 01 00:00:00 EDT 2015},
month = {Thu Oct 01 00:00:00 EDT 2015}
}