Water confinement in hierarchical porous silica and titania

Abstract

In this study, water confinement in hierarchical porous silica and titania is investigated using NMR relaxometry techniques. Results show a greater interaction of water with the TiO₂ surface than with the SiO₂ one. However, regardless of the matrix, the porosity shows no effect on water relaxation. For silica-based materials, two regimes are observed. The first one at low frequency corresponds to a surface diffusion phenomenon and the second one at high frequency is due to the motion of molecules located in a layer of water further from the surface. Concerning mesostructured titania, water relaxation is governed by very slow surface diffusion.