Enhancing Carbon Geosequestration with Supercritical CO ₂ Nanobubbles in Brine

Storing excess CO 2 in underground saline aquifers is an important technology for the low carbon future. Direct dissolution of CO 2 molecules in connate brine (solubility trapping) is a promising carbon geosequestration method, yet the molecular-level understanding was underexplored compared to other macroscopic CO 2 trapping mechanisms. Here, we show that injecting supercritical CO 2 (scCO 2 ) nanobubbles into saline aquifers can considerably boost solubility trapping. Molecular modeling predicts 1.5 to 2× CO 2 oversaturation in brine with the presence of scCO 2 nanobubbles for enhanced CO 2 storage capacity. Furthermore, the nanobubble electrical double layers (EDL) are enhanced by reducing nanobubble sizes and increasing brine salinity, indicating enhanced nanobubble stability against CO 2 macro-phase separation in saline aquifers. The unique physiochemical properties of nanobubbles, including high specific scCO 2 /brine interface areas and low buoyancy forces, also greatly favor the solubility trapping processes. This study highlights that combining nanobubble technology in CO 2 geosequestration is a promising new direction.