Heterostructures Built in Metal Hydrides for Advanced Hydrogen Storage Reversibility

Abstract

Hydrogen storage is a vital technology for developing on‐board hydrogen fuel cells. While Mg(BH4)2 is widely regarded as a promising hydrogen storage material owing to its extremely high gravimetric and volumetric capacity, its poor reversibility poses a major bottleneck inhibiting its practical applications. Herein, a facile strategy to effectively improve the reversible hydrogen storage performance of Mg(BH4)2 via building heterostructures uniformly inside MgH2 nanoparticles is reported. The in situ reaction between MgH2 nanoparticles and B2H6 not only forms homogeneous heterostructures with controllable particle size but also simultaneously decreases the particle size of the MgH2 nanoparticles inside, which effectively reduces the kinetic barrier that inhibits the reversible hydrogen storage in both Mg(BH4)2 and MgH2. More importantly, density functional theory coupled with ab initio molecular dynamics calculations clearly demonstrates that MgH2 in this heterostructure can act as a hydrogen pump, which drastically changes the enthalpy for the initial formation of BH bonds by breaking stable BB bonds from endothermic to exothermic and hence thermodynamically improves the reversibility of Mg(BH4)2. It is believed that building heterostructures provides a window of opportunity for discovering high‐performance hydrogen storage materials for on‐board applications.

Current Research Trends and Perspectives on Solid-State Nanomaterials in Hydrogen Storage

“… Schematic illustration showing the hydrogen storage in nanomaterials and its sustainable applications. Reproducing from ref ([ 12 , 13 , 27 – 29 ], and [ 30 ]) with permission. …”

“…However, these liquid molecules suffer from relatively low hydrogen capacity, intricate hydrogenation and dehydrogenation reactions, and complicated purification processes. In contrast, physical or chemical storing hydrogen into nanomaterials in the solid-state is a competent and practical alternative ( Figure 1 ) [ 10 – 13 ]. The solid-state hydrogen storage exhibits high hydrogen content, safe, easy for handling, transportation, and tradable.…”

Engineering the Oxygen Vacancies in Na2Ti3O7 for Boosting Its Catalytic Performance in MgH2 Hydrogen Storage

“…Unfortunately, the e cient and safe storage of hydrogen with high gravimetric and volumetric capacity poses a major economical bottleneck for the emerging hydrogen economy 4,5 . Solid-state hydrogen storage technology, such as metal hydride 6,7 , metal-organic frameworks 8-10 , or complex hydrides 11 , has deemed to be a promising method for hydrogen storage due to its high-volume hydrogen storage capacity, safety, free of high pressure and heat insulation vessels 12 . Among them, magnesium hydride (MgH 2 ) has been widely regarded as a most promising hydrogen storage material owing to its high gravimetric hydrogen storage capacity (7.6 wt.%), excellent de/rehydrogenation reversibility, low cost, and environmentally friendly [13][14][15] .…”

Engineering oxygen vacancies in Na2Ti3O7 for boosting its catalytic performance in MgH2 hydrogen storage

“…Unfortunately, the e cient and safe storage of hydrogen with high gravimetric and volumetric capacity poses a major economical bottleneck for the emerging hydrogen economy 4,5 . Solid-state hydrogen storage technology, such as metal hydride 6,7 , metal-organic frameworks [8][9][10] , or complex hydrides 11 , has deemed to be a promising method for hydrogen storage due to its high-volume hydrogen storage capacity, safety, free of high pressure and heat insulation vessels 12 . Among them, magnesium hydride (MgH 2 ) has been widely regarded as a most promising hydrogen storage material owing to its high gravimetric hydrogen storage capacity (7.6 wt.%), excellent de/rehydrogenation reversibility, low cost, and environmentally friendly [13][14][15] .…”