High storage capacity and high formation rate of carbon dioxide hydrates via super-hydrophobic fluorinated graphenes

Abstract

Hydrate-based carbon dioxide sequestration technology has attracted widespread attention by promising potential in carbon neutralization process. However, the prerequisite of this technology requires fast CO2 hydrate formation kinetics with high gas absorption capacity. In this study, we compared the promotion effects of four kinds of graphite with different morphologies and hydrophobic properties on hydrate with the objective of identifying a mode for promoting the CO2 hydrate formation based on the properties of gas-liquid interface. The experimental results showed that fluorinated graphene with superhydrophobic nanostructure had the strongest gas storage effect by promoting hydrate nucleation and opening up channels for hydrate sustainable growth. When fluorinated graphene (FG-1) was sufficient to cover the interface sufficiently (1 wt%), the promotion effect was fully developed, resulting in a CO2 storage capacity of 3.53 mmol/g H2O. After combined with surfactant sodium dodecyl sulfate (SDS), 1 wt%FG-1+300 ppm SDS system achieved the best performance, making the gas storage capacity reach 5.02 mmol/g H2O. By observing the formation and decomposition process of hydrate, it was found that fluorinated graphene provided a hydrate formation platform, where the water below passed through the pores between FG-1 nanoparticles, and the gas above was adsorbed or diffused to hydrate formation sites. The modification of the interface by the fluorinated hydrophobic particles improved the solubility of CO2 in water, resulting in the formation of a large number of bubbles in the decomposition process. The special growth process in fluorinated graphene system made hydrate possess excellent CO2 storage performance, which was 1.24–7.56 times that of other nanomaterials. This mode of enhancing mass transfer at the gas-liquid interface provided a novel way to promote the development of hydrate-based applications. At the same time, this work was expected to provide new insights for the development of hydrate-based carbon sequestration technology.