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Title: Towards direct synthesis of alane: A predicted defect-mediated pathway confirmed experimentally

Here, alane (AlH 3) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defect-mediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H 2 and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H 2 dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H 2 exposure, alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH 3 or closely related species at 344 bar H 2, indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 104 bar expected from bulk thermodynamics.
Authors:
ORCiD logo [1] ;  [1] ;  [2] ; ORCiD logo [3] ; ORCiD logo [4] ;  [5] ;  [5] ; ORCiD logo [6] ;  [1] ; ORCiD logo [7]
  1. Ames Lab., Ames, IA (United States)
  2. Ames Lab., Ames, IA (United States); Univ. of Illinois Urbana-Champaign, Urbana, IL (United States)
  3. Univ. of Illinois Urbana-Champaign, Urbana, IL (United States); Ames Lab. and Iowa State Univ., Ames, IA (United States)
  4. Univ. of Illinois Urbana-Champaign, Urbana, IL (United States); Univ. of Pittsburgh, Pittsburgh, PA (United States)
  5. Univ. of Illinois Urbana-Champaign, Urbana, IL (United States)
  6. Univ. of Illinois Urbana-Champaign, Urbana, IL (United States); Univ. of Wisconsin, Madison, WI (United States)
  7. Ames Lab. and Iowa State Univ., Ames, IA (United States)
Publication Date:
Report Number(s):
IS-J-025
Journal ID: ISSN 1864-5631
Grant/Contract Number:
AC02-07CH11358
Type:
Accepted Manuscript
Journal Name:
ChemSusChem
Additional Journal Information:
Journal Volume: 9; Journal Issue: 17; Journal ID: ISSN 1864-5631
Publisher:
ChemPubSoc Europe
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1321966

Wang, Lin -Lin, Herwadkar, Aditi, Reich, Jason M., Johnson, Duane D., House, Stephen D., Pena-Martin, Pamela, Rockett, Angus A., Robertson, Ian M., Gupta, Shalabh, and Pecharsky, Vitalij K.. Towards direct synthesis of alane: A predicted defect-mediated pathway confirmed experimentally. United States: N. p., Web. doi:10.1002/cssc.201600338.
Wang, Lin -Lin, Herwadkar, Aditi, Reich, Jason M., Johnson, Duane D., House, Stephen D., Pena-Martin, Pamela, Rockett, Angus A., Robertson, Ian M., Gupta, Shalabh, & Pecharsky, Vitalij K.. Towards direct synthesis of alane: A predicted defect-mediated pathway confirmed experimentally. United States. doi:10.1002/cssc.201600338.
Wang, Lin -Lin, Herwadkar, Aditi, Reich, Jason M., Johnson, Duane D., House, Stephen D., Pena-Martin, Pamela, Rockett, Angus A., Robertson, Ian M., Gupta, Shalabh, and Pecharsky, Vitalij K.. 2016. "Towards direct synthesis of alane: A predicted defect-mediated pathway confirmed experimentally". United States. doi:10.1002/cssc.201600338. https://www.osti.gov/servlets/purl/1321966.
@article{osti_1321966,
title = {Towards direct synthesis of alane: A predicted defect-mediated pathway confirmed experimentally},
author = {Wang, Lin -Lin and Herwadkar, Aditi and Reich, Jason M. and Johnson, Duane D. and House, Stephen D. and Pena-Martin, Pamela and Rockett, Angus A. and Robertson, Ian M. and Gupta, Shalabh and Pecharsky, Vitalij K.},
abstractNote = {Here, alane (AlH3) is a unique energetic material that has not found a broad practical use for over 70 years because it is difficult to synthesize directly from its elements. Using density functional theory, we examine the defect-mediated formation of alane monomers on Al(111) in a two-step process: (1) dissociative adsorption of H2 and (2) alane formation, which are both endothermic on a clean surface. Only with Ti dopant to facilitate H2 dissociation and vacancies to provide Al adatoms, both processes become exothermic. In agreement, in situ scanning tunneling microscopy showed that during H2 exposure, alane monomers and clusters form primarily in the vicinity of Al vacancies and Ti atoms. Moreover, ball milling of the Al samples with Ti (providing necessary defects) showed a 10 % conversion of Al into AlH3 or closely related species at 344 bar H2, indicating that the predicted pathway may lead to the direct synthesis of alane from elements at pressures much lower than the 104 bar expected from bulk thermodynamics.},
doi = {10.1002/cssc.201600338},
journal = {ChemSusChem},
number = 17,
volume = 9,
place = {United States},
year = {2016},
month = {8}
}

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