Pore size characterization of micro-mesoporous carbons using CO2 adsorption

Pore structure characterization plays a crucial role in the optimization of adsorption properties of nanoporous carbons employed for water purification, gas and liquid phase separations, carbon dioxide reduction, energy storage, and other applications. Here, we present an original methodology for evaluating the pore size distribution in carbons in a wide range of micro- and mesopores from 0.385 to 10 nm from a single isotherm of high-pressure adsorption of CO2 at 273 K. The proposed method is based on the reference theoretical isotherms calculated by Monte Carlo simulations in model pores of slit-shaped and cylindrical geometry. The relationship between the pore size and the pore filling pressure is established. Special attention is given to the predicting of the capillary condensation transitions in mesopores by using the meso-canonical ensemble (gauge cell) Monte Carlo simulations. The proposed technique is demonstrated and verified against the conventional N2 and Ar low temperature adsorption methods drawing on the example of micro-mesoporous carbons of the CMK family. Advantages and limitations of CO2 adsorption characterization of nanoporous materials are discussed and further improvements are proposed.