CO₂ Mixture Adsorption at Single-Walled Carbon Nanotube: Effects from Different Gases and Stoichiometric Ratios

Using adsorption locator for the most stable adsorption site searches, the authors investigated adsorption of mixture of gases with different carbon dioxide mole ratio at a single-walled carbon nanotube (SWCNT). A total of six mixtures were investigated, two mixtures consist of hydrogen, nitrogen and carbon dioxide with compositions 3:1:1 and 3:1:2. Whereas the remaining four mixtures consist of ammonia and carbon dioxide with compositions 5:1, 4:1, 3:1 and 3:2. Results demonstrated that gas interactions with carbon nanotubes increased as the mole ratio of carbon dioxide increased in H₂, N₂ and CO₂ mixture, conversely decreased for NH₃ and CO₂ mixture. After increasing CO₂ mole fraction from 1/5 to 1/3 for hydrogen, nitrogen and carbon dioxide mixture, adsorption energy and rate on carbon nanotube atoms increased by 45 and 33%, respectively, due to a 59% increase in Van der Waal interactions. The preferred molar ratio of H₂, N₂ and CO₂ mixture for adsorption is 3:1:2. The maximum adsorption energy and rate for NH₃ and CO₂ mixture is obtained using the 5:1 sample. Adsorption energy for the NH₃ and CO₂ mixtures increased by 18% when the ratio changed from 3:1 to 3:2 while the adsorption rate decreased considerably.