1. Enhanced hydrogenation properties of two-dimensional MgH2 by doping, vacancy-like defects and strain engineering: A theoretical study.
- Author
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Razouk, Achraf, EL Kassaoui, Majid, Boubkri, Mohammed, Benyoussef, Abdelilah, and Mounkachi, Omar
- Subjects
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THERMODYNAMICS , *DEHYDROGENATION kinetics , *CLEAN energy , *HYDROGEN storage , *DENSITY functional theory - Abstract
Hydrogen storage materials are crucial for the development of clean energy technologies, as they offer a sustainable solution for energy storage. Among various materials, magnesium hydride (MgH 2) offers excellent storage capacity and cost performance. However, its practical application is limited by slow dehydrogenation kinetics and high operating temperatures. To overcome these challenges, novel methods with improved properties are needed. This study aims to explore a two-dimensional (2D) MgH 2 structure and its modifications using density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations. We investigate the thermodynamic stability and dehydrogenation properties of pure 2D MgH 2 , as well as 2D MgH 2 doped with transition metals (Al, Cr, and Nb) and Mg-defects. Additionally, the effects of biaxial strain on pure 2D MgH 2 are explored. The results indicate that the decomposition temperature and stability can be reduced by introducing transition metals, applying biaxial strain, and creating defects. Furthermore, the Cr-doped 2D MgH 2 system exhibits excellent hydrogen storage performance and dehydrogenation kinetics under ambient conditions. It has a formation enthalpy of −39.68 kJ/mol.H 2 , a desorption temperature of 292.53 K, and an hydrogen storage capacity of 7.368 wt%. We also calculated the activation energy for hydrogen diffusion, showing that the lowest value, 0.089 eV, is observed in the Al-doped structure, indicating the fastest hydrogen diffusion among the modifications. These results are helpful for the understanding of absorption/desorption of the 2D MgH 2 system and could ultimately improve the design of Mg-based H 2 -storage materials. [Display omitted] • Stability and dehydrogenation properties of 2D MgH 2 are explored through DFT and AIMD simulations. • Thermodynamic properties were improved by applying compressive/tensile stress, metal doping, and vacancy-like defects. • Cr-doped 2D MgH 2 reaches up to 7.368 wt% with an dehydrogenation temperature of 292.53 K. • The diffusion of hydrogen atom is easier within Al-doped 2D MgH 2 than in other systems. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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