Confinement-induced acceleration of CO₂ mineralization through interfacial water thinning.

Abstract

Current projections demand atmospheric CO₂ removal at the gigatonne-per-year scale through mineral carbonation, yet conventional aqueous routes remain energy-intensive and kinetically limited. Here we apply a water thinning strategy to engineer the interfacial water-film (IWF) with thicknesses below 8.5 nm. We achieve complete carbonation of calcium hydroxide (Ca(OH)₂) within 1 h under ambient conditions, realizing a 16-fold acceleration compared to bulk solution systems. The IWF exhibits confinement-induced saturation kinetics, with the reaction rate increasing with CO₂ partial pressure and then approaching a plateau around 2.02 kPa. Within this film, pocket-like sites in the water confined between particles use oriented interfacial hydroxyls to organize CO₂ and ions, facilitating carbonation even at pCO₂ as low as 0.04 kPa. Crucially, this IWF enables rapid carbonation of industrial alkaline wastes such as carbide slag under ambient conditions, obviating the requirement for pretreatment or other energy-intensive operations. Its demonstrated efficacy across different Ca-rich residues highlights its wide applicability and scalability for CO₂ sequestration. Our findings establish water nanostructuring as a universal platform to unlock Earth-abundant minerals for scalable CO₂ removal applications.