Enhanced Gas Diffusion Coefficient in Water under Tension

Enhancing the gas diffusion in water could benefit a series of biomedical and energy applications but is challenging due to the inherent restriction of water molecules interactions. In this work, we investigate the oxygen and nitrogen diffusivity in water under extreme tension. By encapsulating mesoporous silica with the pore size of 8 nm within polyacrylamide (PAM) hydrogel matrix, we generate large tension in confined water in the mesoporous silica through environmental humidity control. Using pressure-driven permeation tests, we demonstrate up to 4.7-fold and 3.0-fold increases of diffusion coefficients relative to water at normal pressure for oxygen and nitrogen, respectively, under a maximum tensile pressure of -123.7 MPa. Raman spectroscopy and molecular dynamics simulations reveal that tensile stress dissociates large water clusters into smaller species and increases intermolecular spacing, thereby enhancing gas diffusivity. These findings demonstrate a new approach to enhance the gas diffusion in water and offer potential applications in accelerating chemical reactions and advancing tissue engineering.