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Title: First-principles calculated decomposition pathways for LiBH4 nanoclusters

Here, we analyze thermodynamic stability and decomposition pathways of LiBH4 nanoclusters using grand-canonical free-energy minimization based on total energies and vibrational frequencies obtained from density-functional theory (DFT) calculations. We consider (LiBH4)n nanoclusters with n = 2 to 12 as reactants, while the possible products include (Li)n, (B)n, (LiB)n, (LiH)n, and Li2BnHn; off-stoichiometric LinBnHm (m ≤ 4n) clusters were considered for n = 2, 3, and 6. Cluster ground-state configurations have been predicted using prototype electrostatic ground-state (PEGS) and genetic algorithm (GA) based structural optimizations. Free-energy calculations show hydrogen release pathways markedly differ from those in bulk LiBH4. While experiments have found that the bulk material decomposes into LiH and B, with Li2B12H12 as a kinetically inhibited intermediate phase, (LiBH4)n nanoclusters with n ≤ 12 are predicted to decompose into mixed LinBn clusters via a series of intermediate clusters of LinBnHm (m ≤ 4n). The calculated pressure-composition isotherms and temperature-pressure isobars exhibit sloping plateaus due to finite size effects on reaction thermodynamics. Generally, decomposition temperatures of free-standing clusters are found to increase with decreasing cluster size due to thermodynamic destabilization of reaction products.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [3]
  1. National Sun Yat-Sen Univ., Kaohsiung (Taiwan). Dept. of Physics
  2. Univ. of Missouri-St. Louis, St. Louis, MO (United States). Center for Nanoscience and Dept. of Physics and Astronomy
  3. Univ. of California Los Angeles, Los Angeles, CA (United States). Dept. of Materials Science and Engineering
Publication Date:
OSTI Identifier:
1283014
Grant/Contract Number:
FG02-07ER46433; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 6; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
National Sun Yat-Sen Univ., Kaohsiung (Taiwan)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE reversible hydrogen storage; nanoporous carbon; lithium clusters; b-n; destabilization; release; dehydrogenation; nanoparticles; desorption; stability