The aim of this project is to deepen the understanding of ion-solvent interactions and solvation through the use of vibrational spectroscopy, and to develop a solvation term for electrolyte equations of state.
Solvation phenomena are very important in electrolyte solutions, and as many of them are aqueous solutions, the water-salt solvation is of particular relevance. There are today both theories and experimental data for accounting for the solvation effects, however there is no consensus neither on the theoretical nor on the experimental side. These difficulties related to the appropriate assessment of the solvation phenomena severely limit the predictive capabilities of electrolyte models.
More specifically, there have been attempts to formulate models that consider water in ambient conditions as a biphasic liquid that consists of a low-density phase with structured molecules bound together by a hydrogen bond network, and a high-density phase of disordered molecules whose image resembles that of a typical liquid displaying highly local order. While such a model would explain adequately the anomalous behavior of water, there has not been any conclusive evidence to support the two-state theory, as the hydrogen bond network is seemingly very fragile and consists of a small fraction of water molecules under ambient conditions. Furthermore, the role of electrolytes in the two-state theory remains mysterious, as there is speculation that depending on parameters such as the ion species and the concentration, the dissociated ions can either promote the formation of the hydrogen bond network by imposing geometric patterns on the water molecules of the first few hydration shells, or break down the network and induce disorder.
The purpose of this project is to achieve an understanding of the magnitude and nature of solvation phenomena for aqueous electrolyte solutions using both theory, computations and experiments. The experimental work will be based primarily on Near-Infrared spectroscopy and extensive data treatment of the obtained spectra, through the study of the vibration of hydrogen bonds. The modelling/theoretical work will involve an investigation of the solvation terms used in models for electrolytes, both those based on primitive and non-primitive theories.
Main supervisor:
Xiaodong Liang
Co- supervisor:
Georgios Kontogeorgis
Michael Bache