Screening based approach and dehydrogenation kinetics for MgH₂: Guide to find suitable dopant using first-principles...

Area of Science:

• Materials Science
• Computational Chemistry
• Hydrogen Storage

Background:

• Magnesium hydride (MgH2) is a promising material for hydrogen storage due to its high hydrogen capacity.
• However, its practical application is hindered by high dehydrogenation temperatures.
• Surface modification and doping are key strategies to enhance MgH2 kinetics.

Purpose of the Study:

• To investigate the effect of doping at different layers of the MgH2 (110) surface on dehydrogenation kinetics.
• To identify optimal dopants and their positions for lowering hydrogen desorption temperature.
• To understand the underlying mechanisms of doping on MgH2 stability and hydrogen release.

Main Methods:

• First-principles calculations (e.g., density functional theory) to study dehydrogenation barriers.
• Molecular dynamics simulations to assess system stability, bonding, and clusterization.
• Screening based on formation enthalpy, bulk modulus, and gravimetric density.

Main Results:

• Doping at the first and second layers of the MgH2 (110) surface significantly reduces the H2 desorption energy barrier.
• Doping at the third layer shows no significant impact on the barrier energy.
• Aluminum (Al) and Scandium (Sc) were identified as effective dopants, lowering desorption temperature while maintaining desirable material properties.
• Dopant-Hydrogen bonds are primarily covalent, weakening the Mg-Hydrogen bonds.

Conclusions:

• Surface doping, particularly at the top layers, is an effective strategy to enhance MgH2 dehydrogenation kinetics.
• Al is a suitable dopant for improving MgH2-based hydrogen storage materials.
• Layer-dependent doping studies are crucial for discovering advanced reversible hydride materials.