Unique Hydrogen Desorption Properties of LiAlH4/h-BN Composites

Abstract

Hexagonal boron nitride (h-BN) is known as an effective additive to improve the hydrogen de/absorption properties of hydrogen storage materials consisting of light elements. Herein, we report the unique hydrogen desorption properties of LiAlH 4 /h-BN composites, which were prepared by ball-milling. The desorption profiles of the composite indicated the decrease of melting temperature of LiAlH 4 , the delay of desorption kinetics in the first step, and the enhancement of the kinetics in the second step, compared with milled LiAlH 4 . Li 3 AlH 6 was also formed in the composite after desorption in the first step, suggesting h-BN would have a catalytic effect on the desorption kinetics of Li 3 AlH 6 . Finally, the role of h-BN on the desorption process of LiAlH 4 was discussed by comparison with the desorption properties of LiAlH 4 /X (X = graphite, LiCl and LiI) composites, suggesting the enhancement of Li ion mobility in the LiAlH 4 /h-BN composite.

Effects of Defective Boron Nitride Additives on Lithium-Ion Conductivity and Hydrogen-Desorption Properties of LiAlH4

“…As shown in Figure (a), a 40% h-BN composite after milling showed the presence of Al and N throughout the particle. As shown in a previous study, LiAlH 4 was confirmed in the XRD profile . In the STEM analysis, it was difficult to observe diffraction spots from LiAlH 4 because of LiAlH 4 decomposition by an electron beam.…”

“…Li 3 AlH 6 formation was confirmed in the LiAlH 4 /h-BN composite. 19 As shown in the NMR spectrum in Figure 7(c), the LiBH 4 peak was also observed in the h-BN composite. The relative intensity of LiBH 4 peak in t-BN composite was stronger than that in h-BN composite, indicating that a large amount of LiBH 4 phase was formed in the t-BN composite.…”

“…A TG weight loss of 2.6%, 2.4%, and 3.6% was calculated from the profiles of 40 wt % t-BN­(0.5h), t-BN­(2h), and c-BN composite, respectively. A TG weight loss of 3.5% was reported for the 40 wt % h-BN composite . As shown in Figure (a), the DTA profile of the t-BN­(0.5h) composite showed a melting peak at 137 °C, which was lower than the peaks of milled LiAlH 4 (162 °C) and the h-BN composite (151 °C).…”

“…A TG weight loss of 3.5% was reported for the 40 wt % h-BN composite. 19 As shown in Figure 4(a), the DTA profile of the t-BN(0.5h) composite showed a melting peak at 137 °C, which was lower than the peaks of milled LiAlH 4 (162 °C) and the h-BN composite (151 °C). The peak at 137 °C was not synchronized with the DTG curve in Figure S5(a), indicating that the peak cannot be assigned to gas desorption.…”

Functional Materials Based on Metal Hydrides

“…However, aluminium-based complex hydrides were the first complex hydrides to be successfully catalysed. Nakagawa, Isobe, Ohki and Hashimoto recently investigated new types of additive effects of ball milled lithium alanate with hexagonal boron nitride, LiAlH 4 −h-BN [18]. The role of h-BN on the desorption process of LiAlH 4 was discussed in comparison with the desorption properties of LiAlH 4 −X (X = graphite, LiCl or LiI) [18].…”