PREDICTION OF WATER ADSORPTION IN NANOPOROUS CARBONS USING REALISTIC CARBON MODELS

摘要

Water infiltration into hydrophobic confined spaces is critical to the behaviour of a diverse variety of systems such as carbonaceous adsorbents, desalination membranes, separation using nanofluidic devices, and has long been a subject of interest. While its strong adsorption in activated carbons is understood to be due to the presence of hydrophilic polar sites [1], its adsorption and condensation below saturation pressure, observed in the hydrophobic nanospaces of covalently bonded carbons devoid of such polar sites is yet to be explained [2-4]. In particular, while simulations using idealized slit pores show adsorption and condensation at moderate pressures in narrow pores smaller than 1.6 nm in width, this is not found for pores larger pores than 1.6 nm [5]. We demonstrate here, by means of simulations using realistic atomistic models of carbon, that water adsorption and condensation in large pores is a result of disorder and connectivity effects; and is associated with the formation of water clusters sufficiently large to be stable at the windows or nanospaces connecting adjacent pores.