Enhancing Carbon Geosequestration with Supercritical CO₂ Nanobubbles in Brine

Storing excess CO₂ in underground saline aquifers is an important technology for the low carbon future. Direct dissolution of CO₂ molecules in connate brine (solubility trapping) is a promising carbon geosequestration method, yet the molecular-level understanding was underexplored compared to other macroscopic CO₂ trapping mechanisms. Here, we show that injecting supercritical CO₂ (scCO₂) nanobubbles into saline aquifers can considerably boost solubility trapping. Molecular modeling predicts 1.5 to 2× CO₂ oversaturation in brine with the presence of scCO₂ nanobubbles for enhanced CO₂ storage capacity. Furthermore, the nanobubble electrical double layers (EDL) are enhanced by reducing nanobubble sizes and increasing brine salinity, indicating enhanced nanobubble stability against CO₂ macro-phase separation in saline aquifers. The unique physiochemical properties of nanobubbles, including high specific scCO₂/brine interface areas and low buoyancy forces, also greatly favor the solubility trapping processes. This study highlights that combining nanobubble technology in CO₂ geosequestration is a promising new direction.