Anisotropic Dissolution of an Au(111) Electrode in Perchloric Acid Solution Containing Chloride Anion Investigated by in Situ STMThe Important Role of Adsorbed Chloride Anion

Abstract

The anodic dissolution process of Au(111) in a 0.1 M perchloric acid (HClO4) solution containing chloride anion (Cl-) was investigated using an in situ scanning tunneling microscope. The initial dissolution of gold was observed at the step sites when the electrode potentials became more positive than +1.0 V. The rate of the anodic dissolution increased as the potential became more positive. When the potential became more positive than +1.35 V, dissolution on the terraces was also observed. The dissolution of Au(111) anisotropically proceeds in a layer-by-layer mode. Step lines along the [110] direction, which were found in the double-layer region, disappeared, and ones along the [211] direction were newly formed during the dissolution process. The gold surface became rougher when the electrode potential became more positive than +1.45 V, where anodic dissolution and oxide formation simultaneously took place. The gold surface was completely passivated at +1.7 V. The mechanism for the anisotropic dissolution is discussed in relation to the structure of the chloride adlayer on the Au(111) electrode surface.

Stability of underpotentially deposited Ag layers on a Au(111) surface studied by surface X-ray scattering

“…Water was purified using a Milli-Q system (Yamato, WQ-500). Ultrapure N 2 was purchased from Tomoe Shokai Co., Ltd. A Au(111) single crystal disk was purchased from Surface Preparation Laboratory and was used after the treatments as previously reported 3 [40,41]. Prior to each measurement, the Au(111) disk was flame annealed using a Bunsen burner and slowly cooled in air.…”

Atomically Controlled Electrochemical Deposition and Dissolution of Noble Metals

“…In this section, the discussion will be concentrated on the anisotropic layer-by-layer dissolution behavior of noble metal electrodes, palladium and gold, catalyzed by an adlayer of adsorbate on the substrate. Similar anisotropic anodic dissolution processes catalyzed by the ordered adsorbed layer have also been observed on S-Ni(100), [106] I-Ni (111), [107] IAg(100) [108] and Cl-Cu(hkl) [109][110][111][112] as well as Cl-Au(hkl) [29][30][31], which will be discussed in the next section in detail.…”

“…When the crystallographic mismatch of the metal and the substrate is negligibly small, metallic layers are formed on the UPD layer on the substrate by a layer-by-layer growth, namely, the FM mode. When the crystallographic mismatch is relatively large, the UPD layer contains considerable internal strain, and therefore, the growth of the unstrained 3D metal islands on top of the strained UPD layers is energetically favored and this mechanism is called the [29][30][31] [32] [33][34][35][36] [37] [38][39][40] [ [41][42][43][44][45] [26] where A and B denote substrate and metal, respectively. Values in the table are calculated with respect to the gold substrate; c Lattice mismatches AB [26] are shown with respect to that of gold; d The surface-energy mismatches are calculated with respect to a gold substrate following the definition given by Bauer and coworkers [26] as: SK mode.…”

Self-Assembly Process of Flatly Adsorbed Porphyrin Self-Assembled Monolayer on a Au(111) Surface Studied by ex situ Scanning Tunneling Microscopy and Electrochemical Reductive Desorption Measurements

“…[51][52][53] The roughness factor of the surface was estimated from the charge for the reduction of gold oxide to be less than 1.2. 52 The surface modifications of the Au(111) disk substrates were carried out by immersing the substrates in a benzene solution containing 50 µM (M = mol dm ¹3 ) TMMPP, which is a relatively low concentration, at RT for 1 min-90 h.…”