First-Principles Determination of Transference Numbers in Cryolitic Melts

Aïmen Gheribi (1) , Mathieu Salanne (2) , Didier Zanghi (3, 4) , Kelly Machado (3, 4) , Catherine Bessada (3, 4) , Patrice Chartrand (1)

1 Polytechnique Montreal
2 PHENIX - PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX
3 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation
4 UO - Université d'Orléans

The charge and electron transport properties of molten ionic systems are among the most relevant properties to consider in the control of several electrochemical processes. First-principles-based equilibrium molecular dynamics (EMD) can provide reliable predictions of both the total and partial charge transport properties. In this work we calculate the charge transport properties of the electrolytic bath (Na 3 AlF 6-AlF 3-Al 2 O 3) of the Hall-Héroult electrolysis cells. We predict both the individual and collective charge transport properties (total, partial conductivity and self diffusion coefficients) for 11 different compositions typical of industrial conditions via a series of EMD simulations. The predicted total and partial ionic conductivities and their composition dependence are compared to available experimental data. A good agreement is obtained for all studied compositions. From a more fundamental point of view, the microscopic aspect of the charge transport properties of cryolitic melts is discussed through its correlation to the local structure of different melts. Deviations between the calculated partial conductivities and those derived via the Nernst-Einstein approximation can be explained by the presence of strong short-range ordering within the melts.

Domaines: Matériaux

Aïmen Gheribi, Mathieu Salanne, Didier Zanghi, Kelly Machado, Catherine Bessada, et al.. First-Principles Determination of Transference Numbers in Cryolitic Melts. Industrial and engineering chemistry research, 2020, 59 (29), pp.13305-13314. ⟨10.1021/acs.iecr.0c02281⟩. ⟨hal-03014080⟩