Water adsorbed in a commercial carbon: Role of nanostructure and surface chemistry

This article investigates the spatial disposition and mobility of water molecules adsorbed at room temperature in a commercial activated amorphous carbon. Previous wide-angle X-ray scattering measurements are re-examined, together with new observations, in particular by high-resolution transmission electron microscopy, high field solid-state nuclear magnetic resonance, and pulsed field gradient nuclear magnetic resonance. The dry samples are composed largely of deformed turbostratic oxidized graphitic sheets, yielding an array of slit-pores with an average spacing of more than 0.4 nm. All the adsorbed water remains close to the aromatic substrate, and the landscape of adsorption sites is extremely heterogeneous. The water molecules are mobile. Water is initially adsorbed in small confined sites. With increasing relative humidity these develop into clusters that are spatially correlated, which spread and merge, on both sides of the graphitic sheets. [Display omitted]