Using DFT analysis of adsorption data of multiple gases including H2 for the comprehensive characterization of microporous carbons

Abstract

Hydrogen and nitrogen adsorption isotherms at cryogenic temperatures (77 and 87 K) were used to characterize the microporosity of a series of activated carbons, representing various pore size distributions (PSD). The PSD for each carbon was calculated by simultaneous fitting of the DFT model isotherms to their experimental counterparts. The resulting PSD represents robust characteristics of the carbon structure that is consistent with all the data used in the analysis. The range of pore size analysis in this method is extended to smaller pore sizes compared to the standard nitrogen adsorption analysis. In addition, it is shown that this approach allows to detect and exclude experimental points that are not fully equilibrated due to diffusion problems in narrow micropores. The results of the analysis of a series of carbons activated with systematically increasing burn-off show that the presented approach is a useful tool for a comprehensive characterization of microporous carbons, and for obtaining detailed and reliable carbon PSDs.