An in situ STM study on the long-range surface restructuring of Au(111) in a non-chloroaluminumated ionic liquid

We report an in situ STM study of a potential-dependent long-range surface restructuring of Au(1 1 1) electrode in neat 1-butyl-3-methylimidazolium tetrafluoroborates (BMIBF4) ionic liquid. Au(1 1 1) undergoes a significant long-range surface restructuring upon cathodic excursion to -1.0 V vs. Pt quasi-reference. The restructuring involves the formation of tiny pits, which then develops into a stable worm-like network with an average width of the network grids similar to2 nm. Electrochemical annealing occurs at the cathodic limit with the presence of a reduction product of cation BMI+. A smooth surface is recovered with the appearance of the typical (root3 x 22) reconstruction of Au(1 1 1). The surface restructuring is reestablished upon anodic excursion to -1.3 V after the adsorbed reduction product is oxidized. The long-range surface restructuring phenomenon is tentatively explained as a result of partial charge transfer to the weakly adsorbed BMI+, which reduces the metal-metal cohesive energy. In addition, the synergetic effect of the counter anion BF4- may also be involved. The results provide a knowledge of Au(1 1 1) electrode behavior in the neat ionic liquid and are beneficial to understanding in situ STM results involving surface morphological changes in such a media. (C) 2003 Elsevier B.V. All rights reserved.