Nucleation and Growth Process of Water Adsorption in Micropores of Activated Carbon Revealed by NMR

Abstract

Properties of liquids at solid interfaces play a central role in numerous important processes in nature. Nuclear magnetic resonance (NMR) is particularly useful for probing liquid/graphitic carbon interfacial properties. In particular, the nucleus-independent chemical shift (NICS) provides a sensitive measure of the distance between adsorbates and the graphitic carbon surface on the subnanometer scale, enabling NMR to acquire subnanometer scale spatial resolution. Here, by combining the information on thermodynamics obtained from in situ NMR-detected water isotherm and spatially resolved information on structure and dynamics obtained by NICS-resolved NMR, the microscopic process of water nucleation and growth inside the micropore of activated carbons is investigated. The formation of water clusters at surface sites, the cooperative growth process of pore bridging, and the final stage of horizontal pore filling are revealed in detail, demonstrating the potential of this comprehensive NMR approach for studying microscopic mechanisms at solid/liquid interfaces including electrochemical processes.