Effect of pore size and heterogeneous surface on the adsorption of CO2, N2, O2, and Ar on carbon aerogel, RF aerogel, and activated carbons

Aerogels are porous super materials that have many desirable properties including high surface areas which cause them to have significant gas adsorption. In this study, carbon aerogel and resorcinol-formaldehyde (RF) aerogel are compared with six commercial activated carbons (Derived from wood, coconut shells, polymers, and bituminous coal). This study investigates many intrinsic properties of these carbons including surface area, pore size, presence and type of surface groups, as well as ash content and determines their influence on the adsorption of CO2, N-2, O-2, and Ar using pure gas adsorption isotherms. This study noted that there was no trend for ash content but a strong correlation existed between the adsorption capacity and the pore size in the higher pressure region according to Dubinin's micropore volume filling theory. In the lower pressure range, the heterogeneous nature of the surface dominates the adsorption particularly for CO2 which has the strongest polarizability and quadrupole moment of the probe molecules investigated. The two aerogel samples were then further investigated by determining their adsorption in the presence of air using the temperature dependant Toth model with N-2 and O-2 being adsorbed significantly more than CO2 and Ar at ambient conditions, due to their much higher compositions in the air.

Automated summary

This study compared carbon aerogel and RF aerogel with six commercial activated carbons and investigated their adsorption properties. The research found a significant correlation between pore size and adsorption capacity at higher pressures, while surface heterogeneity dominated adsorption at lower pressures. The study also analyzed the adsorption behavior of the aerogels in the presence of air, with N2 and O2 being adsorbed more than CO2 and Ar due to their higher concentrations in the air.