Issue 34, 2015

Mechanochemistry of lithium nitride under hydrogen gas

Abstract

Hydrogen uptake during the mechanochemistry of lithium nitride under 9 MPa hydrogen pressure has been analyzed by means of in situ solid–gas absorption and ex situ X-ray diffraction (XRD) measurements. In situ hydrogenation curves show two H-sorption steps leading to an overall hydrogen uptake of 9.8 wt% H after 3 hours of milling. The milled end-products consist of nanocrystalline (∼10 nm) LiNH2 and LiH phases. The first reaction step comprises the transformation of the polymorph α-Li3N (S.G. P6/mmm) into the β-Li3N (S.G. P63/mmc) metastable phase and the reaction of the latter with hydrogen to form lithium imide: β-Li3N + H2 → Li2NH + LiH. Reaction kinetics of the first step is zero-order. Its rate-limiting control is assigned to the collision frequency between milling balls and Li3N powder. In the second absorption step, lithium imide converts to lithium amide following the reaction scheme Li2NH + H2 → LiNH2 + LiH. Reaction kinetics is here limited by one-dimensional nucleation and the growth mechanism, which, in light of structural data, is assigned to the occurrence of lithium vacancies in the imide compound. This study provides new insights into the reaction paths and chemical kinetics of light hydrogen storage materials during their mechanochemical synthesis.

Graphical abstract: Mechanochemistry of lithium nitride under hydrogen gas

Supplementary files

Article information

Article type
Paper
Submitted
15 May 2015
Accepted
26 Jul 2015
First published
28 Jul 2015

Phys. Chem. Chem. Phys., 2015,17, 21927-21934

Author version available

Mechanochemistry of lithium nitride under hydrogen gas

Z. Li, J. Zhang, S. Wang, L. Jiang, M. Latroche, J. Du and F. Cuevas, Phys. Chem. Chem. Phys., 2015, 17, 21927 DOI: 10.1039/C5CP02812D

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