Molecular Studies and Advanced Visualization of the Trapping of Methane Nanobubbles during Hydrate Growth.

Abstract

The potential application of gas hydrates in storing clean energy has increased the interest in studying clathrate hydrates of gases like methane, CO₂, and hydrogen. In this work, we conduct large-scale molecular studies of methane hydrate growth and visualize the simulation results using mixed reality (MR) headsets and regular two-dimensional snapshots of the simulation domain. The results show the novel molecular observation of the trapping of gas nanobubbles within the growing solid hydrate. Our first-of-a-kind visualization of the internal hydrate structures in mixed reality enabled the length measurements of the simulation domain and nanobubble sizes, which showed that the gas nanobubbles were up to 9 nm in diameter. This is bigger than the simulation domain commonly used in atomistic gas hydrate studies, which explains why this is the first observation of the trapping of methane gas nanobubbles within a growing hydrate. Furthermore, our estimates of the increased storage due to the trapping of the nanobubbles indicate a 37% increase in the weight percentage of methane stored. Although this work focused on nanobubble-enhanced methane storage in hydrates, the idea, methods, and tools developed can be leveraged to enhance the storage of other gases, like hydrogen and CO₂. This study also revealed that the presence of gas nanobubbles accelerates the rate of hydrate formation, which is consistent with experimental observations. Finally, we expect our workflow for MR visualization of gas hydrate structures to facilitate other novel observations and insights from molecular dynamics (MD) studies of gas hydrates.