Effect of Fe additive on the hydrogenation-dehydrogenation properties of 2LiH + MgB 2 /2LiBH 4 + MgH 2 system

J. PUSZKIEL; F. C. GENNARI; P. ARNEODO LAROCHETTE; J. M. RAMALLO LÓPEZ; U. VAINIO; F. KARIMI; P.K. PRANZAS; H. TROIANI; C. PISTIDDA; J. JEPSEN; M. TOLKIEHN; E. WELTER; THOMAS KLASSEN; JOSÉ BELLOSTA VON COLBE; MARTIN DORNHEIM

JOURNAL OF POWER SOURCES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2015 vol. 284 p. 606 - 616

0378-7753

Lithium reactive hydride composite (Li-RHC) has been lately investigated owing to its potential as hydrogen storage medium for a practical application. However, the main problem is its sluggish kinetic behavior. Thus aiming for an improvement of the kinetic behavior, Li-RHC + Fe additive is investigated in the present work. The addition of Fe lowers the starting decomposition temperature of Li-RHC for about 30 ºC and leads to a considerably faster isothermal dehydrogenation rate during the first hydrogen sorption cycle. Through the first hydrogenation, the Li-RHC+Fe material proceeds to the formation of MgH2 and LiBH4, though metallic Fe remains since the formation of an iron boride species might be hindered by kinetic restrictions. Upon the first dehydrogenation, nanocrystalline, well distributed and stable FeB phase is formed, leading to a reduction in the hydrogen capacity. Throughout cycling, the further agglomeration of FeB causes deterioration in the kinetic behavior. An analysis of the hydrogen kinetic mechanism during cycling shows that the hydrogenation and dehydrogenation behavior is influenced by the poor activity of FeB as heterogeneous nucleation center for MgB2 and its non-homogenous distribution in the Li-RHC matrix.