Coarse-grained molecular studies reveal potential for increased CO2 storage in hydrates

The interest in curtailing global warming has accelerated research in capturing and storing carbon dioxide (CO${}_2$), which accounts for 76% of all greenhouse gases. Considering the potential of capturing, storing, and transporting CO${}_2$ as hydrates, several researchers have performed molecular dynamics (MD) and experimental studies of the formation and dissociation of gas hydrates. Although these studies have illustrated essential mechanisms, such as the nucleation and growth of gas hydrates, we show that the small length scales of these studies limit them to processes smaller than the sizes of the domain simulated. To address this limitation, we performed MD studies of CO${}_2$ hydrate growth in systems that are two orders of magnitude larger than in previous studies. This allowed us to observe the trapping of CO${}_2$ nanobubbles within a growing solid hydrate for the first time. We computed the CO${}_2$ density in the trapped nanobubble and observed that it was 2.5 times its corresponding density in the solid hydrate, which indicates the potential to significantly increase the storage of CO${}_2$ (and other gases) in gas hydrates. The CO${}_2$ nanobubbles were bigger than the simulation domains used in most previous MD simulations of CO${}_2$ hydrates, indicating the importance of these large-scale studies.