Capillary Condensation of Water in Mesoporous Carbon

To examine the mechanisms of condensation and evaporation of water in mesoporous carbons without surface functional groups and micropores, we measured gravimetrically the adsorption-desorption isotherms of water on ordered mesoporous carbons with and without surface functional groups and micropores at various temperatures between 265 and 295 K. Water wets partially the pore walls of the mesoporous carbons. Nevertheless, pore condensation of water occurs very slowly at pressures close to or equal to saturation, depending on both the properties of pore walls and the pore size. The uptake of water in the mesoporous carbons without micropores decreases with a decrease in temperature, although the uptake in the mesoporous carbon with micropores does not change at all with temperature. Capillary evaporation of water occurs at pressures expected from the Kelvin equation that describes the link between wetting and capillary condensation.