Characteristic cyclic voltammograms of alkyl viologens at single crystal gold electrodes

Symmetric dialkyl viologens showed characteristic current response in their cyclic voltammograms (CVs) depending on the atomic arrangement of the gold electrode surfaces. Several sharp peaks responsible for the adsorption of the alkyl viologens in the monolayer were observed at Au(111), Au( 100) and Au( 110) electrodes in a potential region that is more positive than the main reduction waves. The current peaks appeared irregularly independent of the alkyl chain length in contrast to the case of mercury and HOPG electrodes. It was pointed out that the CV features of the alkyl viologens were analogous to those of the metal UPD processes, which may reflect similar adsorption processes. The recrystallization occurred more easily on the electrode surfaces in the order Au(110) < Au(111) < Au( 100), which indicated that the states of the bulk accumulated viologen cation radical layer were influenced by the atomic arrangement of the gold electrode surfaces, i.e. the adsorption structure of the first adlayer on them.