Investigation of methane sensing properties of (0,8) single wall carbon nanotube decorated with nickel atoms in the presence of ambient oxygen

Using density functional theory, the effect of nickel decoration of (8,0) single-wall carbon nanotube (SWCNT) has been investigated on improving its sensing properties to methane. Since gas sensors are mainly used in the air environment, all simulations have been performed by considering ambient oxygen as one of the gases in the air. The results show that nickel decoration significantly increases the adsorption energy of methane on the carbon nanotube. The bandgap and work function of the Ni-SWCNT are significantly changed after methane adsorption, which indicates the potential of this metal to improve the sensory properties of carbon nanotubes relative to methane. Investigation of methane adsorption on nickel decorated SWCNT considering the effect of ambient oxygen shows that, while methane adsorption on Ni-SWCNT can reduce the bandgap and work function by 32% and 2.36% respectively, these values are reduced to 16.66 % and 2.34% by considering the effect of ambient oxygen. A comparison of the results shows that nickel decoration of SWCNT has more improvement in the sensory properties of SWCNT to methane gas in the vacuum-based environment rather than air atmosphere. The results also clearly indicate the importance of considering ambient oxygen in the simulation of carbon nanotube-based gas sensors.