Nanobubble size controls gas hydrate nucleation in supercooled water

Abstract

Gas hydrates are crystalline compounds formed when water (H₂O) molecules encapsulate guest gas molecules under high pressure and low temperatures. They have gained significant interest due to their potential as alternative energy resources and their applications in gas storage, transportation, and carbon sequestration. However, the fundamental mechanisms governing their formation, especially the influence of gas bubbles, remain poorly understood. In this study, we use molecular dynamics (MD) simulations to examine how the size of methane (CH₄) nanobubbles modulates hydrate formation in supercooled water. Nanobubbles of different sizes are generated by modulating the CH₄ concentration in a CH₄–H₂O mixture during equilibration simulations under high-temperature and low-pressure conditions, followed by quenching to low temperature and high pressure to induce gas hydrate nucleation and subsequent growth. The simulations reveal a strong correlation between nanobubble size and the extent of hydrate formation. Specifically, the extent of hydrate formation increases with bubble size in the small-to-intermediate regime. However, beyond a critical bubble size threshold, the hydrate formation efficiency declines. The work provides new molecular-level insight into how nanobubble size modulates gas hydrate nucleation and growth dynamics.