KENBIKYO Vol.51▶No.2 2016
■Feature Articles: SPM Coming Close to Atoms on Surfaces, Leaving Vacuum-Environments

Potential-Dependent Local Structure of Electric Double Layer at Electrochemical Interfaces Analyzed by Electrochemical Frequency Modulation AFM

Ken-ichi Fukui

Abstract: Recent development of frequency modulation (FM-) AFM operated in liquid environment enables one to analyze “interfacial liquid structure” in addition to high resolution imaging of the interfacial solid. Using electrochemical FM-AFM we developed in 2010, we have succeeded in analyzing electric double layer (EDL) structures whose local structure varied depending on the applied electrode potential. In this personal account, we focus on the analyses of the EDL at electrolyte aqueous solution / graphite interfaces. It was revealed that a hydrogen-bonding network at the interface greatly perturbed by accumulated anions at anodic potentials (enhanced or disturbed). Besides, such a change in the EDL structure changes the assembly and the redox activity of the adsorbed molecules. Molecular dynamic (MD) simulations of the EDL structure are presented to achieve the molecular scale understanding of such interfacial phenomena.

Key words: electric double layer, hydration, interfacial energy, electrochemical device