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Reversible Metal‐Hydride Transformation in Mg‐Ti‐H Nanoparticles at Remarkably Low Temperatures
Author(s) -
Patelli Nicola,
Migliori Andrea,
Pasquini Luca
Publication year - 2019
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201801186
Subject(s) - activation energy , nucleation , kinetics , hydrogen storage , desorption , hydrogen , hydride , reaction rate constant , metal , chemistry , nanoparticle , analytical chemistry (journal) , materials science , adsorption , inorganic chemistry , nanotechnology , organic chemistry , physics , quantum mechanics
Abstract We study the kinetics of hydrogen sorption in Mg‐Ti‐H nanoparticles prepared by gas phase condensation of mixed Mg‐Ti vapors under a H 2 ‐containing atmosphere. Four samples with different Ti contents from 14 to 63 at.% Ti are examined in the 100–150 °C range. The hydrogen absorption kinetics coupled with the formation of MgH 2 can be described by a nucleation and growth model. The activation energy is in the range 43 - 52 kJ/mol and the rate constant (at 150 °C) increases from 27 ·10 - 3s −1 to 92 ·10 - 3s −1 with increasing Ti content. Hydrogen desorption is well modeled by a sequence of surface‐limited and contracting‐volume kinetics, except at the highest Ti content where nucleation and growth is observed. The activation energy of surface‐limited kinetics is ∼ 32k J /mol. The rate constant (at 150 °C) increases from 0 . 5 ·10 - 3s −1 to 1 . 2 ·10 - 3 s −1 with the Ti content. These results open an unexplored kinetic window for Mg‐based reversible hydrogen storage close to ambient temperature.