Review on Ammonia Absorption Materials: Metal Hydrides, Halides, and Borohydrides

Abstract

Ammonia is well-known as a hydrogen carrier owing to its high hydrogen capacity (17.8 wt %). However, the toxicity and the high storage pressure limit the application of ammonia. Consequently, storing ammonia in solid state has become the promising method to utilize ammonia for practical applications. In this review, ammonia absorption properties of metal hydrides, halides, and borohydrides to form metal amides and metal ammine complexes with various coordination numbers have been systematically summarized. Through this research, we found the correlation between the reactivity with ammonia and the Pauling electronegativity of neutral atoms according to different systems. Metal hydrides with small electronegativity value of the neutral atom of the cations can react with ammonia to form metal amides, which can be used as hydrogen storage material. For metal halides or borohydrides, the lower plateau pressure of ammonia absorption can be obtained in the material with larger electronegativity value of the neutral atom of cations. This useful tendency can be used in the materials design for the potential applications of ammonia-fed fuel cells.

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

“…Rb, Cs, Fr, Sr, Ba, and Ra borohydrides are not included owing to either low capacity (<6 wt.%) or Td higher than 600 • C. In the case of Be borohydride, with~21 wt.% H 2 , it is not included because Be is extremely toxic. As seen, LiBH 4 contains the highest gravimetric capacity but has a relatively high decomposition temperature [1][2][3][4][5][6][7]. However, most of the hydrogen release from LiBH 4 occurs above 500 • C and at a slow rate.…”

“…In the same year, Jin et al were pioneers in successful destabilizing LiBH 4 with CeH 2 [83]. They assessed the theoretical enthalpy change of both LiBH 4 -Ce and LiBH 4 -CeH 2 systems (27.6 and 44.1 kJ mol −1 , respectively) and predicted a significant lower dissociation temperature than the individual hydrides (171 • C versus >350 • C [1]), according to Reaction (7). Experimental studies confirmed that the 6LiBH 4 -CeH 2 composite catalyzed by 0.2TiCl 3 release hydrogen at a temperature lower than LiBH 4 melting forming CeB 6 and LiH as solid products, in agreement with thermodynamic calculations.…”

“…A detailed discussion about the experimental techniques to characterize the nanoconfined hydride Several reviews including borohydrides as potential hydrogen storage materials have been published . They focus on different features such as synthesis [3,7,8,12,15,19,[21][22][23][24][25], crystal structure [3,8,9,11,15,18,19,21,22,26], kinetic and thermodynamic features [2][3][4]10,11,16,17,[20][21][22][23][24][25][26], tailoring their thermodynamic and kinetic behavior [3][4][5][6][7]10,[15][16][17]20,21,[23][24][25]…”

Boron‐ and nitrogen‐doped penta‐graphene as a promising material for hydrogen storage: A computational study

“…Recently, near-total requirement on fossil fuels has brought about two serious trepidations: increased rate of global warming and insecurity of oil imports. [1][2][3] To rectify the two issues, hydrogen is used as an alternate next-generation energy source because its burned by-product is only pure water vapors compared with the carbonaceous fossil fuels. 4 One of the most challenges is the safety and transportation of hydrogen in a compact and affordable storage system.…”

“…These energy sources are invaluable impact of our community toward industrialization. Recently, near‐total requirement on fossil fuels has brought about two serious trepidations: increased rate of global warming and insecurity of oil imports . To rectify the two issues, hydrogen is used as an alternate next‐generation energy source because its burned by‐product is only pure water vapors compared with the carbonaceous fossil fuels .…”