Perovskite-type hydrides ACaH<sub>3</sub> (A = Li, Na): computational investigation on materials properties for hydrogen storage applications.

Abstract

Recently, perovskite materials have emerged as a multifunctional material for photovoltaics, luminescence, photocatalytics and hydrogen storage applications. This work reports a theoretical investigation on materials properties of hydride perovskite ACaH₃ (A = Li, Na) with cubic phase of <i>Pm</i>3̄<i>m</i> space group for application of H₂ storage material. Electronic structure calculations show that the cubic LiCaH₃ and NaCaH₃ have an indirect bandgaps of 2.1 and 2.3 eV with valence band maximum at <i>R</i> point and conduction band minimum at <i>M</i> point. Based on geometric factors, elastic constants and self-consistent phonon calculations, we reveal that ACaH₃ can be dynamically stabilized in cubic phase at elevated temperatures, and the compounds are mechanically stable as well, satisfying Born's stability criteria. Finally, our calculations demonstrate that gravimetric (volumetric) H₂ storage capacities are 5.99 and 4.54 wt% (63.77 and 60.93 g L^-1), and dehydrogenation temperatures are 453.76 and 688.16 K with a consideration of quantum effect for A = Li and Na, respectively. This work highlights that cubic LiCaH₃ is regarded as a potential H₂ storage material due to its high H₂ storage capacity, stability and suitable dehydrogenation temperature.