Arrangement of Al Ions between Ionic Liquid and Graphite Electrode Interface by AFM Force Curve Measurement

Abstract

The arrangement of ions at the interface between highly oriented pyrolytic graphite (HOPG) and Aluminum chloride–1-ehtyl-3-methylimidazolium chloride (AlCl₃–EmImCl) ionic liquid was evaluated using Atomic Force Microscopy (AFM) force curve measurements. In the force curve measurements, three steps were observed towards the HOPG electrode. The width of each step was 0.3, 0.4, and 0.5 nm in order from the final arrival point. Their step widths were regarded as the thicknesses of EmIm⁺, Al₂Cl₇⁻, or their mixed layers. The force curve measurements at each potential demonstrated that the width of the first layer close to the HOPG tended to decrease as the potential shifted towards the less noble side.