Understanding the mechanisms of CaO carbonation: Role of point defects in CaCO₃ by atomic-scale simulations

Rémy Besson (1) , Loic Favergeon (2, 3, 4)

1 UMET - Unité Matériaux et Transformations - UMR 8207
2 SPIN-ENSMSE - Centre Sciences des Processus Industriels et Naturels
3 LGF-ENSMSE - Laboratoire Georges Friedel
4 PRESSIC-ENSMSE - Procédés et REactivité des Systèmes Solide-gaz, Instrumentation et Capteurs

In order to improve our understanding of the mechanisms underlying the carbonation of CaO by CO₂, a practically important reaction, we present a detailed atomic-scale study, by means of ab initio density functional calculations, of the point defect properties in calcite CaCO₃. We perform a thorough investigation of the chemical potentials relevant in experimental conditions. Focusing on C and O defects closely related to CO₂ diffusion, we point out the absence of interstitial C except possibly in complex form with other defects, whereas interstitial O is found stable. Whereas O and C vacancies are not significant in neutral form at low temperature, their role is clearly revealed when charged states are included. The formation energies of O and C vacancies, together with the profiles of chemical potentials across the growing calcite layer, are consistent with joint C and O diffusion by separate vacancy mechanisms of roughly equal amplitudes. As regards the possible influence of complex point defects, our results suggest that interstitial diffusion of CO₂ is unfavorable. Conversely, the strong binding of the CO₂ vacancy may enhance CO₂ diffusion.

Mots clés: simulations; point defects; calcite; CO₂ storage

Domaines: Génie des procédés

Rémy Besson, Loic Favergeon. Understanding the mechanisms of CaO carbonation: Role of point defects in CaCO₃ by atomic-scale simulations. Journal of Physical Chemistry C, 2014, 118 (39), pp.22583-22591. ⟨10.1021/jp506102c⟩. ⟨hal-01100957⟩