Understanding the\nKinetics of CO<sub>2</sub> Hydrate\nFormation in Dry Water for Carbon Capture and Storage: X‑ray\nDiffraction and In Situ Raman Studies

Hydrate-based carbon capture and storage (HBCS) is a\nsustainable\nand promising approach to combating global warming by utilizing water,\nwhich is a ubiquitous resource. Here, we report a comprehensive study\nof CO<sub>2</sub> hydrate formation in dry water (DW), a water-in-air\ndispersion confined in silica particles, for improving the kinetics\nof hydrate growth. Utilizing a combination of a home-built high-pressure\nreactor, in situ Raman spectroscopy, and powder X-ray diffraction\n(PXRD), we elucidate the crystal structure, growth dynamics, and morphology\nof CO<sub>2</sub> hydrates formed in DW, with and without the kinetic\nhydrate promoter, l-tryptophan. Our analysis reveals that\nCO<sub>2</sub> forms structure I (sI) hydrate in DW, with hydrate\ngrowth occurring both on and beneath the silica shell. This results\nin a substantial increase in CO<sub>2</sub> uptakeapproximately\n2.8 times higher than that observed in pure water (∼134 v/v\ncompared to ∼48 v/v). Moreover, incorporation of l-tryptophan in DW formation markedly accelerates the DW-CO<sub>2</sub> hydrate formation process, reducing both the induction time and\nthe time required to achieve 90% gas uptake at 274.65 K. These findings\noffer crucial insights into the formation of CO<sub>2</sub> hydrate\nin DW, highlighting its potential to improve the efficiency and scalability\nof HBCS technologies.