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Hydrate-based CO2sequestration (HBCS) technology is one promising method for reducing the CO2level in the atmosphere for climate mitigation. However, the sluggish kinetics and low conversion rate of the CO2hydrate hindered its practical applications. This study presents an innovative approach by coupling magnesium (Mg) with an amino acid l-leucine (l-Leu) to speed up the CO2hydrate nucleation and realize the ultrarapid CO2growth in the static system. The addition of a Mg sheet speeds up CO2hydrate nucleation, resulting in an induction time less than 10 s compared with traditional ∼10 h in a static system. The coupling Mg sheet with l-Leu (1.0 wt %) shows optimal synergistic promotion effects on both CO2hydrate nucleation and growth. The resulting final CO2gas uptake is 78.9 Vg/Vwcompared with 67.8 Vg/Vwwithout Mg. However, the t90used is significantly shortened to 1.4 h compared with a t90of 13.0 h without Mg. We further analyzed the possible promotion mechanism of Mg using a series of analytical methods, including Mg sheet surface morphology observation with element composition analysis, gas phase compositions analysis by GC and Mg2+concentration in aqueous phase by ICP-MS. Corrosion of the Mg sheet surface is observed based on SEM images. A significant reduction of Mg is identified in the element composition analysis with additional C and N after corrosion. A small trace of hydrogen (∼1%) is identified in the gas phase with the Mg2+in solution reaching 68 mg/L. Based on the experimental evidence, we propose that the abundant H2bubbles released from the surface of the Mg sheet due to corrosion in the acidic environment of CO2solution are one critical factor explaining the ultrarapid nucleation observed. Our study demonstrated that employing Mg corrosion to assist the nucleation of CO2hydrate is effective in the static system and the coupling of amino acid can further enhance CO2hydrate kinetics. The developed method can also be utilized for other hydrate-based technologies, such as flue gas separation and hydrogen storage, by coupling Mg with suitable promoters.

CO2hydrates hold promising applications, including as a medium for carbon storage in oceanic sediments, as a result of their high storage capacity. However, the presence of high salinity in sediments is likely to affect the CO2hydrate kinetics. To counter this challenge, the CO2hydrate formation, dissociation, and deep morphology have been investigated in seawater (SW) under static and non-static conditions. Moreover, the effect of a kinetic promoter [1000 ppm of l-tryptophan (l-tryp)] and a thermodynamic promoter (5 wt % 1,3-dioxane) and dual promotional effects of kinetic and thermodynamic promoters (1000 ppm of l-tryp + 5 wt % 1,3-dioxane) have also been studied. In situRaman spectroscopy was used to probe the real-time CO2dissolution in seawater in the presence of 1,3-dioxane. The CO2uptake in seawater for the static system was estimated to be in the following order (20 h): CO2(30.5 ± 5.0 mmol/mol) > CO2+ 1000 ppm of l-tryp (30 ± 1.20 mmol/mol) > CO2+ 1,3-dioxane + 1000 ppm of l-tryp (26.2 ± 7.1 mmol/mol) > CO2+ 1,3-dioxane (21.1 ± 6.1 mmol/mol). In comparison, for the non-static system, the CO2uptake in seawater was estimated to be in the following order (20 h): CO2+ 1000 ppm of l-tryp (67.8 ± 2.20 mmol/mol) > CO2+ 5 wt % 1,3-dioxane (49.3 ± 7.0 mmol/mol) > CO2+ 5 wt % 1,3-dioxane + 1000 ppm of l-tryp (42.9 ± 4.8 mmol/mol) > CO2(39.5 ± 4.1 mmol/mol).