Argon adsorption behavior of multi-walled carbon nanotubes with different diameters

Multi-walled carbon nanotubes (MWCNT) with two different average diameters were purified with the nitric acid (MWCNT-HNO3) treatment process. The N2 (adsorption/desorption) measurement showed an increase in surface area from the raw material to the MWCNT 4 normal (4N) acid (HNO3) treatment material, and a decrease in surface area from the MWCNT-4N acid treatment material to the MWCNT-8N acid treatment material. Transmission electron microscopy (TEM) analysis implies that some amorphous carbons have been removed from the treated samples and defects on the sidewalls were observed. We conducted a study of the adsorption of argon onto multi-walled carbon nanotubes of different diameters, using the volumetric method. The specific surfaces were measured by the BET method; the calculation of the adsorption capacity and energy were made. The analysis of these parameters revealed that the surface area, the adsorption capacity and the adsorption energy are inversely proportional to the diameter of MWCNT. Those results were compared to the adsorption of hydrogen onto the MWCNT. We found that the results do not match and conclude that argon cannot be stored on MWCNT.