Toward an understanding of high-pressure CO2 hydrate

CO2 clathrate hydrate is one of the most intensively studied hydrates due to its potential application for gas storage and its importance in planetary science. However, its pressure-induced transformation pathway remains obscure. The literature presents contradictory reports, with three different structures of high-pressure CO2 hydrate identified under nearly identical conditions. Although single-crystal X-ray diffraction (SC-XRD) is the only technique capable of unambiguously addressing these issues, CO2 hydrates have been examined exclusively using powder diffraction (both X-ray and neutron) and Raman spectroscopy. Here, we propose to conduct in-situ high-pressure and low-temperature SC-XRD experiments to accurately constrain the high-pressure behavior of CO2 hydrate and further explore the phase diagram of the CO2-H2O system.