Adsorption simulation of open-ended single-walled carbon nanotubes for various gases

In order to study the adsorption capacity of open-ended single-walled carbon nanotubes for various gases, the grand canonical Monte Carlo method is used to simulate the adsorption capacities of methane, nitrogen, water, carbon dioxide, and carbon monoxide in different types of open-ended single-walled carbon nanotubes at temperatures of 273.15 K and 298.15 K and pressures of 1 Pa–101.325 kPa. Gas adsorption isotherms under various conditions were obtained. The effects of temperature and diameter of open-ended single-walled carbon nanotubes on gas adsorption capacity were discussed. The results showed that the open-ended single-walled carbon nanotubes had a certain adsorption capacity for five kinds of gases under low pressure conditions. For a given temperature, as the diameter of the tube increased, the adsorption capacities of various gases were enhanced. Each gas exhibited different growth gradients; specifically, the growth gradients of methane and nitrogen were relatively small, while the growth gradients of water, carbon dioxide, and carbon monoxide were relatively large. With an increase in the temperature, the adsorption capacities of CH4, N2, H2O, and CO2 exhibited a downward trend, while the adsorption capacity of CO was not affected by temperature, keeping a stable value. The open-ended single-walled carbon nanotube with a diameter of 10.85 Å exhibited a high adsorption capacity for CO, and it could be used as a porous material for storing or separating CO.