First principles calculation of perovskite‐type hydrides KXH₃ (X=Al, Cu) for hydrogen storage applications

Laboratory of Condensed Matter and Interdisciplinary Sciences, Unité de Recherche labellisée CNRST, URL-CNRST-17, Faculty of Sciences, Mohammed V University of Rabat, Morocco.

Abstract

The primary objective of this paper is to characterize the perovskite-type hydrides KXH₃ (X=Al, Cu) and explore their potential for hydrogen storage applications using density functional theory (DFT). The study investigates various aspects such as structure, electronic and optical properties, stability, and hydrogen storage capabilities. To accomplish this, the study employs the Perdew–Burke–Ernzerhof-Generalized Gradient Approximation (PBE + GGA) functional. The KAlH₃ compound is optimized in a cubic crystal structure, yielding lattice constants of 7.55 Å. On the other hand, KCuH₃ is optimized in a tetragonal crystal structure with dimensions of a=b=11.14 Å and c=13.23 Å. These materials exhibit stability, as indicated by their negative formation energy. The electronic properties of KXH₃ (X=Al, Cu) are thoroughly investigated, including the determination of bandgap, total density of states, and partial density of states. Notably, these structures exhibit a metallic character. The optical results reveal that these novel materials demonstrate minimal energy loss and high conductivity. Regarding hydrogen storage capabilities, the gravimetric hydrogen storage values for KXH₃ (X=Al, Cu) compounds are found to be 4.38 and 2.86 wt%, respectively. These findings suggest that KAlH₃ shows promise as a potential candidate for hydrogen storage applications.