Characterization of activated carbons with low-temperature hydrogen adsorption

Low-temperature nitrogen adsorption isotherms are widely used for characterization of carbon materials. However, quite complex physical mechanism of interaction of nitrogen with graphite and micropores hinders a reliable pore size distribution (PSD) analysis. This situation is worsening by a strong regularization procedure which effect on the PSD function is basically unknown. In the present paper we propose a new method of the PSD analysis of activated carbons in the micropore range using hydrogen adsorption isotherms at 77 K. We relied on the kinetic Monte Carlo simulation and accurately accounted for the McLachlan surface mediation, quantum correction of the H2 - C potential, and the reduced carbon collision diameter (0.26 nm) determined previously (Ustinov E. Carbon 2016; 100: 52). Analysis of PSDs of several samples of activated carbons has shown that the microporous structure of investigated materials consists of discrete number of slit micropores of specified width. We noted that a population of micropores having width of 0.67-0.69 nm is often observed. This suggests that this group of pores can appear due to burn-off of one layer in the graphite lattice. The kernel for the PSD analysis is presented in the form of regression equation which can be used by researches independently.

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