Giant osmotic pressure in the forced wetting of hydrophobic nanopores

TL;DR

This paper investigates the extreme osmotic pressures observed during forced wetting of hydrophobic nanopores, revealing a molecular exclusion mechanism that significantly enhances energy storage capabilities.

Contribution

It demonstrates that molecular exclusion causes a breakdown in nanopores, leading to unprecedented osmotic pressures that improve energy storage in hydrophobic nanoporous materials.

Findings

Molecular exclusion dominates in subnanometric pores.

Osmotic pressure law accurately predicts intrusion/extrusion pressures.

Electrolyte solutions significantly enhance energy storage capacity.

Abstract

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.