The adsorption of 4,4ʹ-bipyridine at a Cd(0001)|ionic liquid interface – The descent into disorder

Abstract

In this study, electrochemical impedance spectroscopy and in situ STM measurements have been used to investigate the interface between a Cd(0001) single-crystal electrode and an ionic liquid electrolyte containing an organic additive. The addition of 4,4ʹ-bipyridine clearly influenced the interfacial structure and properties by forming an adlayer on the surface of the electrode during the experiment. Furthermore, in the potential range under study, the organic adlayer of adsorbed 4,4ʹ-bipyridine undergoes structural changes, as seen in both cyclic voltammograms and capacitance–potential curves. The processes occurring on the interface were further visualised using in situ STM, and the formation of 4,4ʹ-bipyridine agglomerates on the electrode’s surface was observed. The results underline the impact of the electrolyte characteristics (water vs. ionic liquid) on the adsorption of organic additives and the formation of adlayers.

Keywords

• Ionic liquids
• EMImBF4
• Cadmium surface
• Adlayers