Surface Speciation of α-Al2O3 (11̅02) in Contact with Liquid Water

Abstract

Surface speciation of the (11¯02$1\overline{\mathrm{1}}02$$1\overline{\mathrm{1}}02$) α-Al₂O₃ surface in contact with liquid water has been investigated with DFT-MD simulations. The coupling with theoretical HD-SFG spectroscopy of the aqueous interface has revealed the relative proportions of surface aluminol terminations of μ₁OH+2${}_2^{+}$${}_2^{+}$, μ₁OH, μ₂OH, and μ₃OHs that are populating the aqueous top-surface at PZC conditions. In this journey, SFG at the interface with the air has also been utilized and pKs of the aluminols have been revisited. All knowledge thus acquired has allowed us to rationalize the pH-dependency of the HD-SFG signatures of the (11¯02$1\overline{\mathrm{1}}02$$1\overline{\mathrm{1}}02$) α-Al₂O₃ aqueous surface.