Huijun Han

Huijun Han

Affiliation: Ulsan National Institute of Science & Technology (UNIST)

Research Interests:  Atomic scale investigation on ion-water interaction, Charge-dependent properties of atoms and molecules

Title: Salt dissolution at atomic scale

Abstract: Ion-water interactions are fundamental to electrochemistry, catalysis, battery, and biology. However, conventional experiments in aqueous solutions at the macroscopic level averages out hydration numbers, structures, and effective charges of ions. Recent studies using scanning tunneling microscopy present an atomic view of the hydration and transport of Na+ ion [1] as well as the specific ion effect on hydration structures [2,3]. Despite these advances, the microscopic understanding of salt dissolution in water–one of the simplest and well-established reactions–has remained elusive due to the statistical ensemble of aqueous solutions. In this talk, I will discuss the atomic-scale investigation on the salt dissolution, by controlling a single water molecule (H2O) at an under-coordinated site of a sodium chloride (NaCl) [4]. Precise manipulation of H2O molecules on NaCl surface provides the insight into ion-water interactions and the surface dynamics of the molecules, which are responsible for the selective dissolution of anions in real space. Our results indicate that the polarizability difference between Na+ and Cl− ions contributes to the bond characteristic and cleavage of the ionic bonds by one H2O molecule. The water dipole attracts an electron cloud of Cl− ion engaging in the ionic bonds, weakening the bond strength and facilitating the dissolution of the Cl− ion. This study provides the microscopic mechanism of the salt dissolution.