Enhanced oxygen solubility in metastable water under tension

TL;DR

This study directly measures oxygen solubility in metastable water confined in nanopores, revealing a two-fold increase at moderate subsaturation, confirming thermodynamic predictions under strong confinement and negative pressures.

Contribution

First direct measurement of oxygen solubility in confined metastable water, validating thermodynamic models under extreme conditions.

Findings

Oxygen solubility doubles at RH ~ 0.55

Thermodynamic predictions agree with measurements under confinement

Implications for oxygen-dependent processes in natural and industrial systems

Abstract

Despite its relevance in numerous natural and industrial processes, the solubility of molecular oxygen has never been directly measured in capillary condensed liquid water. In this article, we measure oxygen solubility in liquid water trapped within nanoporous samples, in metastable equilibrium with a subsaturated vapor. We show that solubility increases two-fold at moderate subsaturations (RH ~ 0.55). This evolution with relative humidity is in good agreement with a simple thermodynamic prediction using properties of bulk water, previously verified experimentally at positive pressure. Our measurement thus verifies the validity of this macroscopic thermodynamic theory to strong confinement and large negative pressures, where ignificant non-idealities are expected. This effect has strong implications for important oxygen-dependent chemistries in natural and technological contexts.