Understanding the Hydrophilicity and Water Adsorption Behavior of Nanoporous Nitrogen-Doped Carbons

Abstract

Through molecular simulation we exposed the anomalous water adsorption behavior in slit-shaped and disordered nitrogen doped carbons. Instead of Langmuirian, water adsorption proceeds via mechanisms analogous to crystal nucleation: birth and spread of (poly) nucleation sites in one, two, and three dimensions forming water nanowires/pillars and water clusters before complete pore filling via capillary condensation. The adsorption of water and the adsorption hysteresis in N-doped carbons are strongly influenced by the pore-size. The smaller the pore-size, the smaller is the pressure at which the above-mentioned process tends to occur in N-doped carbons. The nucleation analogues are clearly visible in a pore that has a homogeneous pore structure, whereas in disordered pore structures, the complex and distributed pore-sizes disturb these nucleation analogue patterns especially at lower relative pressures. The effect of the adsorbed water molecules on the connectivity of the available pore volume is discussed....