Dynamics of water and ethanol in graphene oxide

TL;DR

This study investigates how water and ethanol molecules move within graphene oxide using neutron scattering, revealing reduced diffusivity, temperature effects, and anisotropic diffusion behaviors in confined environments.

Contribution

It provides detailed insights into the diffusion dynamics of water and ethanol in graphene oxide, including anisotropy and the existence of mobile and immobile fractions, using advanced neutron scattering techniques.

Findings

Reduced diffusivities of water and ethanol in GO

Evidence of mobile and immobile liquid fractions

Faster diffusion perpendicular to membranes

Abstract

We utilized the momentum transfer(Q)-dependence of Quasi-Elastic Neutron Scattering (QENS) to reveal the dynamics of water and ethanol confined in Graphene Oxide (GO) powder or membranes at different temperatures and in different orientations. The dynamics was measured across different length and time scales using several spectrometers. We found reduced diffusivities (up to 30\% in the case of water) and a depression of the transition temperatures. While water showed near Arrhenius behavior with an almost bulk-like activation barrier in a temperature range of 280-310 K, the diffusivity of ethanol showed little temperature dependence. For both water and ethanol, we found evidence for immobile and mobile fractions of the confined liquid. The mobile fraction exhibited jump diffusion, with a jump length consistent with the expected average spacing of hydroxide groups in the GO surfaces. From anisotropy measurements, we found weak anisotropy in diffusion, with the surprising result that diffusion was faster perpendicular to membrane than parallel to it.