  The forced intrusion of water in hydrophobic nanoporous pulverulent material
is of interest for quick storage of energy. With nanometric pores the energy
storage capacity is controlled by interfacial phenomena. With subnanometric
pores, we demonstrate that a breakdown occurs with the emergence of molecular
exclusion as a leading contribution. This bulk exclusion effect leads to an
osmotic contribution to the pressure that can reach levels never previously
sustained. We illustrate on various electrolytes and different microporous
materials, that a simple osmotic pressure law accounts quantitatively for the
enhancement of the intrusion and extrusion pressures governing the forced
wetting and spontaneous drying of the nanopores. Using electrolyte solutions,
energy storage and power capacities can be widely enhanced.
