Magnesium-Promoted Rapid Nucleation of Carbon Dioxide Hydrates

Gas hydrates offer solutions in areas like CO2 sequestration and desalination. However, their formation is severely limited by long induction (wait) times for nucleation, which range from hours to days. Many existing nucleation promotion techniques involve chemical additives, which invite environmental and process-related concerns. Here, we report a simple, passive, and environmentally friendly technique to significantly promote the nucleation of CO2 hydrates: magnesium (in pure and alloy forms) triggers nucleation almost instantaneously. We report induction times of less than 1 min, which is the fastest induction time reported for any gas hydrate under stagnant conditions. This translates to Mg-promoted nucleation rates being 3000 times higher than the baseline. Statistically meaningful measurements of nucleation kinetics (in milliliter and liter-scale reactors), direct visualization of nucleation, and X-ray photoelectron spectroscopy (XPS)/Fourier-transform infrared spectroscopy (FTIR) analysis uncover several chemistry-related insights associated with Mg-based promotion. Importantly, the three-phase line of magnesium–water–CO2 gas is key to promotion. Porous oxide layers, generation of H2 nanobubbles, and chemisorption of CO2 on Mg surfaces are other factors responsible for accelerated nucleation. Interestingly, Mg alloys exhibit faster nucleation promotion than pure Mg, which is significant in salt water medium. Overall, our work opens up pathways for faster synthesis of hydrates, which is critical to realizing applications.