Studies of the hydrogen energy storage potentials of Fe- and Al-doped silicon carbide nanotubes (SiCNTs) by optical adsorption spectra analysis

Abstract

This work investigated the hydrogen adsorption potentials of the Fe-doped (magnetic) and Al-doped (nonmagnetic) armchair silicon carbide nanotubes (SiCNTs) as candidates for hydrogen storage materials. Calculations of the electronic transport properties of the investigated systems were performed using the popular density functional theory as implemented in quantum ESPRESSO while corrections to quasi-particle energies were performed using Yambo codes within many-body perturbation theory. The obtained results of the structural properties revealed that pristine single-walled SiCNT was found to be more stable due to its higher binding energy of −393.85 eV while less stability was recorded with Al-doped SiCNT having binding energy of −393.81 eV. Furthermore, the stability of the Fe-doped SiC nanotube was found to be normal between bond lengths 1.73 Å to 1.79 Å, indicating its great potential to accommodate more Fe dopants. In terms of electronic properties, the Fe-doped SiC nanotube demonstrated half-metallic and half-monometallic properties. Ferromagnetic features were also observed for the Fe-doped SWSiCNT when Fe replaced the Si atoms, while antiferromagnetic features were observed when Fe replaced the C atoms. The results obtained from optical spectra analysis indicated that Fe-doped SiCNT adsorbed hydrogen only at 1.8 eV which is the lower part of the visible spectrum while Al-doped SiCNT adsorbed hydrogen at energy levels 0 eV, 2.8 eV and 7.1 eV which extended from visible to UV regions. Therefore, Al-doped SiCNT is recommended as a better candidate for hydrogen storage under ambient conditions.