porous carbons; hysteresis

This study investigates the origin of low-pressure hysteresis (LPH) in the adsorption and desorption of threedifferent probe molecules: CO2, N2, and Ar, across various adsorption temperatures (from cryogenic to roomtemperature), and within five different carbon materials: synthetic carbons (pristine and one post-syntheticallyoxidized) and natural coal. Significant attention is dedicated to elucidating LPH in oxidized samples outgassed atvarious temperatures (120–350 °C). Experimental results show that insufficient outgassing temperature can leadto unreliable data due to artificial LPH and significantly underestimated textural properties, primarily caused byporosity blockage from substances like moisture. Conversely, in samples where heteroatoms have a stabilizingeffect of texture, such as natural coal, careful consideration of outgassing temperature is crucial due to the risk ofthermal degradation. Other factors contributing to LPH are adsorption temperature, and especially, kineticlimitations at cryogenic temperatures for cellulose-based carbons. Minor factors responsible for LPH are thephysical state of the sample (monolith vs. powder) and the flexibility of the porous system, both studied by CO2sorption.This study constitutes an important piece in the evaluation of LPH, providing practical recommendations andunderlining the importance of experimental design, with implications for further research in this complex field[1].

This study investigates the origin of low-pressure hysteresis (LPH) in the adsorption and desorption of threedifferent probe molecules: CO2, N2, and Ar, across various adsorption temperatures (from cryogenic to roomtemperature), and within five different carbon materials: synthetic carbons (pristine and one post-syntheticallyoxidized) and natural coal. Significant attention is dedicated to elucidating LPH in oxidized samples outgassed atvarious temperatures (120–350 °C). Experimental results show that insufficient outgassing temperature can leadto unreliable data due to artificial LPH and significantly underestimated textural properties, primarily caused byporosity blockage from substances like moisture. Conversely, in samples where heteroatoms have a stabilizingeffect of texture, such as natural coal, careful consideration of outgassing temperature is crucial due to the risk ofthermal degradation. Other factors contributing to LPH are adsorption temperature, and especially, kineticlimitations at cryogenic temperatures for cellulose-based carbons. Minor factors responsible for LPH are thephysical state of the sample (monolith vs. powder) and the flexibility of the porous system, both studied by CO2sorption.This study constitutes an important piece in the evaluation of LPH, providing practical recommendations andunderlining the importance of experimental design, with implications for further research in this complex field[1].