Enhanced Low-Temperature Hydrogen Storage in Nanoporous Ni-Based Alloy Supported LiBH4

Abstract

To reveal the synergistic effect of nanoconfinement and metallic catalysis on the hydrogen storage properties of LiBH 4 , the nanoporous Ni-based alloy (np-Ni) was prepared herein by dealloying of the Mn 70 Ni 30 alloy in (NH 4) 2 SO 4 solution, and then LiBH 4 was loaded into np-Ni to construct the LiBH 4 /np-Ni hydrogen storage system using wet impregnation. It was found that dehydrogenation of the LiBH 4 /np-Ni (1:5) system starts at around 70 • C and ends before 400 • C, with ∼11.9 wt.% of hydrogen desorbed. The apparent dehydrogenation activation energy for the LiBH 4 /np-Ni (1:5) system was remarkable decreased to about 11.4 kJ/mol. After rehydrogenation at 450 • C under 8 MPa hydrogen pressure, ∼8.2 wt.% of hydrogen can be released from about 60 • C upon second dehydrogenation. These obtained results would provide an efficient strategy for improving the hydrogen storage properties of other metal borohydrides.

Pore Filling of a Carbon Matrix by Melt-Impregnated LiBH4

“…Figure 5 illustrates this statement: if pore filling occurred gradually along the radius (because a LiBH 4 film grew thicker at the interface), then the free pore size measured by nitrogen isotherms would be reduced concomitantly with the pore volume (as observed by Chen et al). 25 The appearance of the isotherm in Figure 2 might suggest an H1-type hysteresis, meaning that the pores are cylindrical. The surface of a tube (2π•r•h) can vary linearly with one of its parameters if the other remains constant.…”

“…Interestingly, Chen et al observed that the size of the pore in a nickel porous matrix was lowered from 7.2 to 1.8 nm when the pores were wet impregnated by LiBH 4 (5:1 w/w). 25 This suggests that, depending on the filling method or the matrix nature, the filling of the pores by LiBH 4 might follow very distinct processes. Cahen et al wet impregnated a carbon matrix with LiBH 4 and observed significant differences in the material's behavior; nonetheless, as they did not present the nitrogen adsorption of the infiltrated material, those differences cannot be attributed to the filling method.…”

“…Counterintuitively, it means that the diameter of the pores does not contract gradually while their volume decreases, as would be expected if layers of LiBH 4 grow thicker on pore sides. Interestingly, Chen et al observed that the size of the pore in a nickel porous matrix was lowered from 7.2 to 1.8 nm when the pores were wet impregnated by LiBH 4 (5:1 w/w) . This suggests that, depending on the filling method or the matrix nature, the filling of the pores by LiBH 4 might follow very distinct processes.…”

“…LiBH 4 is an intriguing hydride material that behaves surprisingly and presents a considerable hydrogen capacity (13.6 up to 18.4 wt % H 2 ) . Yet, it performs inappropriately, with sluggish kinetic properties that affect both working temperature and reversibility. , Diverse approaches have been exerted to bypass these limitations: heteroatom destabilization, metal catalysts, hydride mixtures, and nanoconfinement, − and ultimately, these methods were combined. − Each strategy performed well in some aspects of the challenge but never managed to improve sufficiently every operational characteristic of the material (onset temperature, liberation kinetics, and reversibility) while always having a cost over its mass capacity. In this aspect, wrapping (i.e., in graphene foil) is an appealing refinement of nanoconfinement as its impact on weight is limited. − As illustrated by Zhang et al, the synergistic activation of LiBH 4 is a tantalizing opportunity that offers to break the bottleneck of each individual method …”

Destabilization of Boron-Based Compounds for Hydrogen Storage in the Solid-State: Recent Advances

“…% under constant heating at 380 • C in 1 h. Metallic Ti and Ti 3+ species were formed during dehydrogenation, which destabilized the ionic bond between Li + and [BH 4 ] − . Other examples of scaffolds are an Ni-nanoporous alloy and silica MCM-41 [159,160].…”