Surface carbonation governs olivine reactivity for rapid CO2 mineralization

Ultramafic rocks are a global resource with vast potential for permanent CO 2 mineralization. However, the origin of the striking reactivity difference between Ca- and Mg-bearing olivine remains poorly understood. Here we show that this difference arises not merely from the type of cation, but more fundamentally from how these cations modulate the oxygen reactivity. Nonbridging oxygens serve as the oxygen source for CO 2 surface reactions, which in Ca-olivine reduce the Ca 2+ dissolution barrier by 60% and accelerate ion release by six orders of magnitude. The calculated apparent dissolution rate constants reproduce the experimentally observed complete conversion of Ca-olivine within hours under 1 atm CO 2 . This multiscale framework reveals how surface reactions govern silicate carbonation and provides a predictive basis for modeling and engineering large-scale CO 2 mineralization in both synthetic materials and basaltic reservoirs.