Role of Early-Stage Atmosphere in the Dehydrogenation Reaction of the LiBH₄–YH₃ Composite

Abstract

This article investigates the dehydrogenation behavior of the LiBH4–YH3 composite under various early-stage Ar back-pressure conditions. It is clearly observed that a minute change in early-stage atmosphere greatly affects the overall dehydrogenation reaction of the composite. Free boron and Li2B12H12 start to form in turn as the partial dehydrogenation products around 400 °C under static vacuum or low Ar back pressure. The formation of Li2B12H12 greatly increases the activation energy for the dehydrogenation reaction between LiBH4 and YH3 into LiH and YB4, hence significantly retarding the reaction. The formation of B just slightly increases the incubation period of the reaction. The formation of Li2B12H12 is effectively suppressed by initially applying Ar back pressure above 0.1 MPa.

Tuning LiBH4 for Hydrogen Storage: Destabilization, Additive, and Nanoconfinement Approaches

“…The reversibility of pristine LiBH 4 demands harsh conditions (>600 • C and >100 bar H 2 ) [1,41], which makes it impossible for its direct use as a hydrogen storage medium for practical applications. Several investigations have been done heading towards thermodynamic destabilization and kinetic improvement of LiBH 4 [29,30,39,46,49,50,53,[58][59][60][61][62][63][64][65][66][67]69,[72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][89][90][91][92][93][94][95][96][97][98][99].…”

Fundamental Material Properties of the 2LiBH4-MgH2 Reactive Hydride Composite for Hydrogen Storage: (II) Kinetic Properties

“…In the literature, the formation of volatile Ti(BH 4 ) 3 from the interaction between LiBH 4 and Ti halides has been also proposed [44,45]. However, it has been already reported that the presence of H 2 overpressure suppresses the further formation of volatile species [46][47][48]. Moreover, Kang et al and Karimi et al have found that the interaction between titanium fluorides (TiF 3 and TiF 4 ) and Li-RHC promotes the formation of nanosized TiB 2 during milling [49,50].…”

Microstructural Characterization of Dehydrogenated Products of the LiBH4-YH3 Composite

“…Although it is hard to identify LiBH 4 , free boron and Li 2 B 12 H 12 from the diffraction patterns, a high resolution TEM image gives direct evidence for free crystalline B that is a product of the selfdecomposition of LiBH 4 (Fig. A considerable amount of Li 2 B 12 H 12 from the partial decomposition of LiBH 4 might also be present in the matrix considering the previous results of Raman spectroscopy Kim et al, 2011Kim et al, , 2013, although the regions of Li 2 B 12 H 12 are not clearly identified in the matrix presumably due to its amorphous character. Although it was not possible to obtain microstructural evidence for the formation of Li 2 B 12 H 12 by TEM analysis, an EELS spectrum from the matrix region of the sample (point 3 in Fig.…”

“…Vajo et al (2005), Pinkerton et al (2007), and Bösenberg et al (2010) observed that hydrogen back pressure enhances the formation of MgB 2 during dehydrogenation and dehydrogenation pathway of the LiBH 4 -MgH 2 composite is dependent on temperature. In addition, it was observed that the increase in hydrogen back pressure up to 0.4 MPa enhances dehydrogenation kinetics of the LiBH 4 -YH 3 composite (Kim et al, 2011(Kim et al, , 2013. It was also reported that rehydrogenation is achieved under relatively mild temperature and pressure conditions after dehydrogenation under 0.3 MPa of hydrogen.…”

“…In previous studies Shim et al, 2010;Kim et al, 2011Kim et al, , 2013, it was reported that the LiBH 4 -YH 3 , LiBH 4 -CeH 2 and LiBH 4 -CaH 2 composites experience different dehydrogenation reaction pathways under static vacuum and 0.3 MPa of hydrogen. Formation of Li 2 B 12 H 12 as an intermediate dehydrogenation product is known to retard the dehydrogenation kinetics of the LiBH 4 -YH 3 composite by blocking the contact between LiBH 4 and YH 3 (Kim et al, 2011(Kim et al, , 2013. In addition, it was observed that the increase in hydrogen back pressure up to 0.4 MPa enhances dehydrogenation kinetics of the LiBH 4 -YH 3 composite (Kim et al, 2011(Kim et al, , 2013.…”