Séminaire Programme Gradué Chimie PSL

Zoom link : https://espci.zoom.us/j/85635514099?pwd=dHhMVHQxbENRVkc0amxCelg5cEN2Zz09
ID de réunion : 856 3551 4099
Code secret : 102958

Abstract: The dynamic response to applied electrical potentials is a topic of fundamental significance in many systems, from supercapacitors and batteries, to the understanding of electrokinetics. Many electrokinetic systems of interest involve the application of alternating potentials. In this seminar I will discuss the dynamic response to an applied oscillatory electric field of monovalent salt solutions confined between two walls, investigated by using a modified Surface Forces Apparatus. In opposition to what could be anticipated from purely electrostatic considerations, we observed a strong, slowly evolving repulsive force between surfaces separated by an aqueous electrolyte upon application of an alternating potential difference between the walls. This long-range repulsive force increases with the ratio of diffusion coefficients of the ions in the medium and the square of the applied potential. We argue that the repulsive force is a consequence of the field-induced ionic excess in the gap, due to ionic transport from adjacent reservoirs.