Charge Dynamics in Electrified Water and Their Impact on Interfacial Properties

Interfacial phenomena of liquids result from the imbalance of intermolecular forces experienced by molecules in the bulk and at the surface of a liquid. The introduction of electrical charges in such a system can significantly alter these forces, leading to changes in physicochemical properties, such as surface tension and vapor pressure. Therefore, investigating the charging of liquids, particularly ultrapure water, has become an important area of scientific research due to its implications for various applications. Water carrying a measurable electrical charge can be produced by several methods, including triboelectrification, electrohydrodynamic liquid bridges, and electrohydrodynamic atomization (EHDA). Here, we explore the application of EHDA as a liquid charging mechanism. The charged water yields a charge density of 0.37 mC·L–1. Raman spectroscopy reveals transient spectral changes consistent with hydrated-proton-associated structures and/or charge-induced reorganization of the hydrogen-bond network, while Kelvin-probe measurements independently confirm persistent positive electrostatic charging of the water surface. Contact-angle measurements indicate a substantial decrease in the apparent surface tension, reaching 40.31 ± 6.14 mN m–1 for charged water. This value should not be interpreted as a direct measurement of the thermodynamic surface tension because electrostatic deformation, charge redistribution, and nonequilibrium wetting may also influence the measured contact angle. Consequently, the molecular mechanism underlying the observed change cannot be assigned uniquely from the present measurements. Electrostatic potential maps obtained using an electrostatic probe have shown that added charge can remain stable up to hours at the water surface.