Pint = −2γcosθ

Abstract: High pressure water intrusion in hydrophobic nanoporous media have been studied in relation with energy storage. It has already been showed that addition of electrolytes in water increases intrusion pressure of liquid leading to an en-hancement of storing capacities. We demonstrate here that for a number of salt, a very simple van ’t Hoff law can explain in-trusion and extrusion excess pressures compared with the pure water case. Our results suggest that only pure water can pen-etrate the pores, the ions being quartered in the bulk liquid around nanoporous medium. This selectivity explains very high pressures for very concentrated ions reported elsewhere. 1 Fi-nally, a partial intrusion of NaI and LiI is observed. This effect could be explained on the basis of particular behaviour or iodide ions over hydrophobic surfaces. Heterogeneous Lyophobic systems (HLS), based on forced intrusion and spontaneous extrusion cycles of a nonwetting fluid in a nano-porous media, are particularly appealing for either storage or dissipation of mechanical energy.2,3 Storage of energy coincides with the intrusion step while its restora-tion coincide with the extrusion step (see figure 2). Different behaviours can be observed with either a low hysteresis, of interest for energy storing,4 or a high hysteresis of interest for damping applications.5,6 LHS can be seen as nanolaboratories to probe fluid trans-port, nucleation, phase changes, and more generally inter-facial phenomena in nano or sub nanoconfinement. LHS allowed to demonstrated that the macroscopic Laplace-Washburn equation is still usable at nanoscale to predict intrusion pressure:7,