Sc- and Ti-doped silicon carbide nanotubes for NH3 sensing and storage applications: a DFT approach

Ammonia (NH3) is highly hazardous gases, thus the investigation for a highly sensitive sensor of NH3 molecule is desirable. The adsorptions of NH3 molecule on Sc and Ti atoms doped silicon carbide nanotube (SiCNT) were investigated by using density functional theory calculation. The adsorption energies, adsorption distances, energy gaps, chemical hardness and softness, orbital distributions, charge transfers and density of states were examined. The calculated results display that NH3 molecules can be adsorbed on the pristine SiCNT via a weak physical interaction, which is much weaker than those of NH3 adsorption on Sc and Ti-doped SiCNTs. All of Sc and Ti-doped SiCNTs can absorb single and multiple NH3 molecules with the greatest adsorption energy of − 41.56 kcal/mol for NH3/TiSi–SiCNT system. In addition, there are shorter adsorption distance and larger charge transfer for Sc- and Ti-doped SiCNTs than that of pristine SiCNT with NH3 molecule. The orbital distributions are occurred around the doping site may be due to the strong interaction between NH3 and SiCNT. The energy gaps of Sc- and Ti-doped SiCNTs have much more significant change than that of pristine SiCNT in which 2NH3/TiC–SiCNT show the largest change of energy gap about 22% compared with bare TiC–SiCNT. The density of states of Sc- and Ti-doped SiCNTs show significant shift than that of pristine SiCNT which the new impurity states near the − 2.5 eV is occurred. The chemical hardness and softness illustrate the enhancement stability and decreased the reactivity. A short recovery times and suitable desorption temperatures are observed for the NH3 desorption on Sc- and Ti-doped SiCNT surface. Therefore, sensitivity to NH3 molecule of Sc- and Ti-doped SiCNTs is a promising candidate for highly sensitive gas sensing and storage nanomaterials. Graphical abstract