PORE-SIZE DISTRIBUTION ANALYSIS OF MICROPOROUS CARBONS - A DENSITY-FUNCTIONAL THEORY APPROACH

We present an improved method, based upon density functional theory, for the determination of the pore size distribution (PSD) of porous sorbents. The adsorption isotherms predicted by nonlocal mean field theory for individual slit pores are correlated as a function of pressure and pore width. The PSD is then calculated by fitting this correlation to the experimental adsorption isotherm of the sorbent. We apply the analysis method to adsorption data for nitrogen on several porous carbons. In this application, the porous network is modeled as a continuous size distribution of noninteracting slit-shaped graphitic pores. The PSDs obtained by using the Kelvin equation and using the local and nonlocal versions of the mean field density functional theory are compared and evaluated. The results demonstrate that nonlocal theory provides a more accurate interpretation of the PSD than previous methods have achieved, particularly when the analysis is applied to highly microporous sorbents.