Calorimetry and molecular simulation for the characterization of SWCNT by CO2 adsorption

ANDRÉS A. GARCÍA BLANCO; A.G. ALBESA; DEBORA A SOARES MAIA; J. VILLARROEL ROCHA; J.L. VICENTE; KARIM SAPAG

Delray Beach (FL)

Workshop; 6th International Workshop – Characterization of Porous Materials – From Angstroms to Milimeters; 2012

In this work single walled carbon nanotubes (SWCNT) were subjected to an acid treatment in the conditions reported in previous studies and characterized by CO2 adsorption at 273 K, N2 adsorption at 77 K and thermal analysis. Adsorption isotherms and differential enthalpies of CO2 adsorption were measured in a Tian-Calvet microcalorimeter connected to a volumetric system which allows the simultaneous measurement of adsorption isotherms and enthalpies of adsorption. In addition, the surface chemistry of the materials was studied by temperature programmed decomposition and the effect of surface groups in gas adsorption was discussed. Additionally, molecular simulations of gas adsorption in SWCNT were performed, using the Monte Carlo method in the Grand Canonical ensemble. Heterogeneous bundles of nanotubes were employed as substrate for the simulations, using distributions of nanotubes diameters similar to the diameters experimentally determined. The simulations were performed for the adsorption of N2 at 77 K and CO2 at 273 K. Simulated adsorption isotherms as well as isosteric heats of adsorption profiles were obtained. The results from Monte Carlo simulation gave information about the kind of adsorption sites in SWCNT available for each gas. Additionally, the correlation between experimental and simulated isotherms gave information about the nanotubes diameter distribution, which is important for the characterization of SWCNT.