Electronic structure and stability of a pure sodium alanate clusters Na12Al12H48, and the interstitial space-doped with Ti, C and H atoms, as a promising hydrogen storage system: Density functional theory

• Published in: International journal of hydrogen energy 2023-06, Vol.48 (53), p.20430-20440
• Main Author: Mekky, Abdel-baset H.
• Format: Article
• Language: English
• Subjects: DFT calculations; Electronic structure and stability; Hydrogen storage; Sodium alanate clusters (Na12Al12H48); Ti, C, and H- Interstitial doped
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.03.023

Sodium alanate is a complex aluminium hydrogen, which has recently attracted more attention because it can be used as an effective hydrogen storage material. Our goal is to investigate the electronic structure and stability characteristics of promising hydrogen storage materials, including sodium alanate, Na12Al12H48 (12 units of NaAlH4), and which doped (interstitial defects) with Ti, C, and H atoms. The B3lyp/Sto-3G density functional theory based on quantum mechanical calculations uses DFT to obtain crucial information on chemical stability and reactions, such as possible structures (optimal bond length), electronegativity (ω), hardness (η), softness (S), ionization potential (IP), electron affinity (EA), energy gap (Eg), electronic chemical potential (μ), Fermi energy level (EF), maximum charge transfer (ΔN max), work function (ɸ), and electrophilicity (χ). These DFT-based global reactivity descriptors are sufficient to provide a better understanding of chemical systems in terms of their stability and reactivity. The interstitial doping by these atom positions places all binding lengths without any other significant change from the Na12Al12H48 crystal structure. Na12Al12H48 sodium lanate is slightly distorted. Na12Al12H48–H is very reactive and stability is low. The Na12Al12H48 –H cluster is expected to be promising in the formation of new compounds. On the other hand, the higher band gap values found for pure Na12Al12H48 clusters correspond to greater stability. Analysis of the length of the bonds and electronic properties shows that the sodium alanate grid was relatively uninfluenced by the interstitial space enriched with Ti, C, and H atoms. These results also show that the role of the C, Ti, and H atoms added to sodium alanates is not a “interstitial space doping” element but a catalyst. •Investigated electronic structure & stability of Na12Al12H48 & interstitial space-doped with Ti, C, H using DFT.•Cage structures not distorted in optimal geometries for interstitial space-doped clusters.•Pure Na12Al12H48 clusters found to be more stable than interstitial space-doped.•Interstitial space-doped atoms act as catalysts, not “doping” elements.•Na12Al12H48 cluster has lower chemical reactivity and greater stability than interstitial space-doped clusters.