Investigating the hydrogen storage potential and optoelectronic properties of double perovskite ZMg2FeH8 (Z = Ca, Be) hydrides

Abstract

Hydrogen presents a compelling solution to the growing energy scarcity and environmental problems as a clean and sustainable energy source. Among various storage methods, solid-state hydrogen storage holds promise but necessitates extensive investigation. However, to enhance the performance of these systems, metal hydrides with high gravimetric densities, favorable thermodynamics, and rapid kinetics are essential. The novelty of this work is the systematic comparison of the CaMg 2 FeH 8 and Be 2 MgFeH 8 hydrides by using the CASTEP calculation tool based on first-principles, which includes the assessment of hydrogen storage, structural, XRD, molecular dynamic simulations, electronic (Hybrid-HSE 06), Mulliken population analysis, optical, and thermodynamic properties of ZMg 2 FeH 8 (Z = Ca, Be) under 0, 35, and 70 GPa pressure for hydrogen storage applications. Structural investigation confirms structural stability, while XRD patterns confirm phase stability over varying pressure ranges. The calculated gravimetric capacities of CaMg 2 FeH 8 and BeMg 2 FeH 8 5.2837 wt% and 6.6343 wt%, respectively. CaMg 2 FeH 8 and BeMg 2 FeH 8 show the hydrogen desorption temperatures of 460.7 K and 476.4 K. Molecular dynamic simulations and thermodynamic analysis validate dynamical and thermal stability under 0–70 GPa pressure. Electronic properties reveal that both ZMg 2 FeH 8 (Z = Ca, Be) exhibits the semiconductor nature. Optical study indicates significant absorption in the UV spectrum. These findings present ZMg 2 FeH 8 (Z = Ca, Be) compounds as strong candidates for hydrogen storage applications and a gateway for experimental researchers to the advancement of sustainable energy technologies.