Thanks to its abundance, low weight, high-energy density, and pollution-free burning, hydrogen is considered to have great potential as an alternative energy carrier . One of the main challenges for the mobile use of hydrogen is the development of an effective and safe material for hydrogen storage .
Lithium borohydride (LiBH4) has been recognized as a possible contender for hydrogen storage materials , thanks largely to its high gravimetric (18.5 wt.%) and volumetric (121 kg H2/m3) hydrogen density.
However, the real-world use of LiBH4 as a hydrogen storage medium is hindered  by its unfavorable high thermal stability (for example, its decomposition peak temperature of ~470 °C).
For that reason, a number of methods, including reactant destabilization, catalyst/additive introduction, nanostructuring, and anion/cation substitution have been utilized to reduce the dehydrogenation temperature and accelerate the kinetics .
Nanoengineering has been shown to be an effective method through which to reduce the dehydriding/rehydriding temperature of LiBH4, which is achieved by shortening diffusion path lengths and making surface areas larger .
Nonetheless, nanoscale LiBH4 is overly-sensitive and reacts strongly to the water and oxygen in the air, which hinder its practical application. Optimal gas selectivity was found in PMMA (Poly (methyl methacrylate)), with a high permeability ratio of H2/O2 .
As a result, PMMA was used in this study to shield LiBH4 from oxygen and water, while still allowing hydrogen to flow in and out unimpeded (Scheme 1). In addition to this, the nanoconfinement of LiBH4 in the fine network pore of PMMA and the interaction between the B atom in LiBH4 and the O atom in C=O of PMMA caused a far lower hydrogen discharge temperature of LiBH4.
LiBH4 PMMA composite began to dehydrogenate at 53 oC and discharged 5.2 wt.% of hydrogen at 162 oC within 1 hour. This study offers a broad-spectrum approach through which to use a gas-selective polymer to shield air-sensitive hydrogen storage compounds and advance their hydrogen storage properties.
Scheme 1. Schematic illustration of LiBH4 protected from oxygen and water by PMMA.
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