Computational investigation of comprehensive properties of AlX3H9(X = Ca, Sc, Zr) materials for high-performance hydrogen storage

Hydrogen energy is highly potential in carrying a big weight in future energy market due to its wonderful environmental friendliness and applicable flexibility. In order to search promising hydrogen storage materials with desirable hydrogen storage capacity and desorption temperature, we have studied a new class of Al-based materials AlX 3 H 9 (X = Ca, Sc, Zr) with simple cubic structures. The phonon dispersion spectra of AlCa 3 H 9 and AlSc 3 H 9 show imaginary frequency, which is the indicator of instability. However, when the lattice anharmonic effect is involved, all three materials actually exhibit good stability at certain higher temperatures. Besides, a frequently-used hydrostatic pressure is another solution to the imaginary frequency. The materials are ductile compounds with metallic bonding nature, which ensures the potential application in flexible devices. The electronic band structure suggests they are metallic, except for AlCa 3 H 9 with a narrow bandgap of 0.316 eV. The gravimetric hydrogen densities (GHD) are 5.76 wt% for AlCa 3 H 9 , 5.27 wt% for AlSc 3 H 9 and 2.91 wt% for AlZr 3 H 9 . The hydrogen release temperatures for most favorable desorption pathways are 280.0 K for AlCa 3 H 9 , 325.1 K for AlSc 3 H 9 and 132.2 K for AlZr 3 H 9 , respectively. The comprehensive results suggest that AlCa 3 H 9 and AlSc 3 H 9 are suitable candidates for hydrogen storage because of their large storage capacity and moderate desorption temperature in favor of practical application. • Novel AlX 3 H 9 (X = Ca, Sc, Zr) are studied by first-principle calculations for hydrogen storage. • Finite-temperature phonon spectra are calculated to discuss the structural stability of the hydrides. • Gravimetric hydrogen storage capacities are 5.76 wt% for AlCa 3 H 9 and 5.27 wt% for AlSc 3 H 9 . • The hydrogen desorption temperatures are 280.0 K for AlCa 3 H 9 and 325.1 K for AlSc 3 H 9 .