An Atomistic Description of the γ-Alumina/Water Interface Revealed by Ab Initio Molecular Dynamics

Brice Firmin Ngouana-Wakou (1) , P. Cornette (2) , Manuel Corral Valero (1) , D. Costa (2) , Pascal Raybaud (1)

1 IFPEN - IFP Energies nouvelles
2 ENSCP - Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL

We report ab initio molecular dynamics (AIMD) simulations of the (100) and (110) γ-Al2O3/water interfaces at 300 K, using two sets of supercell models for each surface and two time lengths of simulation (10 and 40 ps). We first show that the effect of liquid water on the vibrational frequencies of hydroxyl groups at the interface varies according to the type of surface. This trend is explained by two key parameters affecting the interaction of both surfaces with water: the nature of the OH groups (i.e., μ1-OH, μ1-H2O, μ2-OH, and μ3-OH) and H-bond network among surface OH groups. The hydroxylated (110) surface favors the local structuration of water at the interface and the solvation of its μ1-OH and μ1-H2O groups by water similarly as in bulk liquid water. By contrast, on the (100) surface, a stronger H-bond network among μ1-OH and μ1-H2O groups reduces the water/surface interaction. We illustrate also how the interfacial interacting sites are spatially organized on the surfaces by two-dimensional maps of O–H distances. On both surfaces, the interfacial water layer orientation is predominantly Hup–Hdown. For long AIMD simulation time, Grotthuss-like mechanisms are identified on the (110) surface.

Domaines: Chimie

Brice Firmin Ngouana-Wakou, P. Cornette, Manuel Corral Valero, D. Costa, Pascal Raybaud. An Atomistic Description of the γ-Alumina/Water Interface Revealed by Ab Initio Molecular Dynamics. Journal of Physical Chemistry C, 2017, 121 (19), pp.10351 - 10363. ⟨10.1021/acs.jpcc.7b00101⟩. ⟨hal-01760310⟩