First Principles Investigation of NH3 and NO2 Adsorption on Transition Metal-Doped Single-Walled Carbon Nanotubes

Density functional theory calculations were carried out to investigate the binding ability of transition metals (TM = Cr, Mo, W, Mn, Tc, and Re) on (5,5) armchair single-walled carbon nanotubes (SWCNTs) and their adsorption ability with ammonia (NH3) and nitrogen dioxide (NO2). The geometric, electronic, and energetic properties of pristine SWCNT doping with TM and their NH3 and NO2 adsorptions were calculated to explore their potentials as gas adsorptions and sensors. The binding abilities of TMs to the SWCNT are found to be in the order: Cr > Mo > Tc > Re > W > Mn. According to the results, compared to the pristine SWCNT, TM atom doping can significantly increase gas adsorption ability in which W-SWCNT has the strongest interaction, and the ability to absorb NO2 is higher than NH3. The density of states and orbital distributions display that the band gaps and electron delocalizations of TM-SWCNTs are significantly changed upon gas adsorption. These observations suggest that the TM-doped SWCNTs can be introduced as promising candidates in gas adsorptions and sensor devices for storage and detecting NH3 and NO2 molecules.