Additive Effects of TiCl₃ on Dehydrogenation Reaction of LiAlH₄

Abstract

Recently, LiAlH 4 has attracted attention as one of the most promising hydrogen storage materials, because LiAlH 4 is able to release large amount of hydrogen (7.9 mass%H 2 ) below 250°C. However, the kinetics of the dehydrogenation reaction of LiAlH 4 is too slow for applications to fuel cell vehicles. To improve the dehydrogenation kinetics, the dopant effect of TiCl 3 has been investigated in this research. Here, LiAlH 4 doped with various ratios (0, 0.1, 0.2, 0.5, 1.0, and 2.0 mol%) of TiCl 3 were prepared by ball milling for 30 min under a 1.0 MPa H 2 atmosphere. The decomposition of LiAlH 4 proceeds via a two-step reaction and the dehydrogenation kinetics of each step were compared to determine the optimum amount of TiCl 3 that would assist the process. With increasing of TiCl 3 amount, the dehydrogenation temperature for both of the reactions decreased. Activation energies decreased with increasing TiCl 3 amount, however the amount of desorbed hydrogen decreased. Considering the kinetics and hydrogen capacity in the both steps, the results suggest that the optimum amount of doped TiCl 3 for the dehydrogenation of LiAlH 4 is around 0.2 mol%.

Unique Hydrogen Desorption Properties of LiAlH4/h-BN Composites

“…Since Bogdanović et al reported an absence of hysteresis and nearly horizontal pressure plateaus in the TiCl 3 -doped NaAlH 4 [7], many researchers have studied complex hydrides including alanate as potential reversible hydrogen storage materials. In the case of LiAlH 4 , the improved desorption kinetics was reported by the doping of Ti catalyst using mechanically milling [10][11][12]. Recent study also reported a single step hydrogen release of LiAlH 4 , which was induced by the synergetic effects of Ti catalytic coating and nanosizing effects [13].…”

Enhanced dehydrogenation of LiBH 4 ·NH 3 –LiAlH 4 composites

“…Among alanates, LiAlH 4 has a relatively high theoretical hydrogen density (10.5 wt.%) [18] in comparison with NaAlH 4 (7.4 wt.%) and KAlH 4 (5.7 wt.%) [19]. By the two-step decomposition reaction, 7.97 wt.% hydrogen could be released from LiAlH 4 at moderate temperature (160e220 C) [20,21].…”

Improved hydrogen storage performances of LiAlH 4 + Mg( BH 4 ) 2 composite with TiF 3 addition

“…Based on the dehydrogenation study, LiAlH 4 doped with 0.5 mol% TiCl 3 displays the largest decrement in the onset decomposition temperature and starts to desorb hydrogen at 91 C, which is 88 C lower than the as-received LiAlH 4 . Meanwhile, LiAlH 4 + 0.5 mol% Ti shows the least reduction with an initial dehydrogenation temperature of 119 C. Furthermore, Isobe et al 41 studied the dehydrogenation of LiAlH 4 doped with various ratios of TiCl 3 (0, 0.1, 0.2, 0.5, 1.0, and 2.0 mol%). They report that the most effective amount of TiCl 3 in enhancing the desorption properties of LiAlH 4 is 0.2 mol%.…”

“…Meanwhile, LiAlH 4 + 0.5 mol% Ti shows the least reduction with an initial dehydrogenation temperature of 119°C. Furthermore, Isobe et al 41 studied the dehydrogenation of LiAlH 4 doped with various ratios of TiCl 3 (0, 0.1, 0.2, 0.5, 1.0, and 2.0 mol%). They report that the most effective amount of TiCl 3 in enhancing the desorption properties of LiAlH 4 is 0.2 mol%.…”