Designing high-capacity hydrogen storage materials: DFT insights into Ca-based complex hydrides MCa <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:mrow> <mml:msup> <mml:mi mathvariant="normal">M</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:mrow> </mml:math> H6 (M <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"> <mml:mrow> <mml:mo linebreak="goodbreak" linebreakstyle="after">=</mml:mo> </mml:mrow> </mml:math> Li, Na; <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"> <mml:mrow> <mml:msup> <mml:mi mathvariant="normal">M</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:mrow> </mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"> <mml:mrow> <mml:mo linebreak="goodbreak" linebreakstyle="after">=</mml:mo> </mml:mrow> </mml:math> Co, Rh, Ir)
Asif Hosen, Ebrahim Nemati‐Kande, Hanof Dawas Alkhaldi, Ahmad A. Mousa, Ali Akremi, Imed Boukhris, Mohammed S. Abu-Jafar
Abstract
In this study, density functional theory (DFT) is utilized to explore the structural, electronic, optical, mechanical, thermodynamic, and hydrogen storage properties of MCa H 6 (M Li, Na; Co, Rh, Ir) double perovskite-type hydrides for the first time. The structural analysis confirms that all the studied materials crystallize in the cubic phase with space group 216 (F m). The phonon dispersion analysis confirms that five hydrides LiCaRhH 6 , LiCaIrH 6 , NaCaCoH 6 , NaCaRhH 6 , and NaCaIrH 6 demonstrate dynamic stability, while LiCaCoH 6 shows the presence of soft modes. Furthermore, ab initio molecular dynamic (AIMD) simulations confirmed the thermal stability of the studied materials, showing no structural deformation. All compounds exhibit indirect bandgap semiconductor behavior based on their electronic properties, while a reduction in bandgap is observed when the cationic atom at the M and -site in MCa H 6 is substituted. The mechanical properties findings reveal that all the hydrides are mechanically stable and exhibit brittle behavior. We employed the Quasi-Harmonic Debye model to analyze the thermodynamic behavior across different temperatures, and the results align well with fundamental thermodynamic principles. The hydrogen storage characteristics reveal that the studied materials LiCaCoH 6 , LiCaRhH 6 , LiCaIrH 6 , NaCaCoH 6 , NaCaRhH 6 , and NaCaIrH 6 exhibit storage capacities of 5.40, 3.38, 2.47, 4.72, 3.52, and 2.31 wt%, respectively, demonstrating their potential suitability for hydrogen storage applications. Our findings reveal that LiCaCoH 6 is the most suitable material for H 2 storage, as it not only demonstrates the highest storage capacity within the proposed materials but also surpasses the target values established through the US Department of Energy (DOE).