Dynamics of Metastable Nanoscale Island Growth and Dissolution at Electrochemical Interfaces by Time-Resolved Scanning Tunneling Microscopy

Abstract

The dynamics of nanoscale island growth, stability, and dissolution, accompanying the potential-induced phase transitions between the (22 × 3) and (1 × 1) structures of the Au(111) surface in 0.1 M HClO 4 solution, have been investigated by potential pulse perturbation time-resolved scanning tunneling microscopy (P 3 TR-STM). Starting from a potential at which the reconstructed (22 × 3) phase is stable, a short positive potential pulse briefly brings the electrode to a potential at which the (1 × 1) phase is stable. This pulse induces a perturbation that lifts the Au(111)-(22 × 3) reconstruction completely, resulting in nanoscale island formation on the surface. The nanoscale islands are metastable and dissolve with time. The initial average island area and the island decay rate are related to the pulse amplitude and duration. The higher and longer the pulse, the smaller the average size of the islands produced and the more slowly the islands decay. This result reveals a "voltammetric annealing" process that may be important in stable island formation at electrochemical interfaces. The dynamics of individual islands are quite heterogeneous and nonmonotonic. Small islands decay faster than large islands. Even under metastable conditions, large islands frequently grow before ultimately decaying, providing evidence for electrochemical Ostwald ripening in this system. A simple model, based on perimeter detachment as the rate-limiting step, provides a qualitative explanation for the observed decay dynamics.

Dynamics of Porphyrin Electron‐Transfer Reactions at the Electrode–Electrolyte Interface at the Molecular Level

“…For example, the reduction of pre-adsorbed oxidized TPyP can be very slow, taking as long as tens of minutes at À0.05 V. However, the oxidation of adsorbed TPyP at 0.2 V is much faster, occurring in seconds. (The potential for the onset of oxidation of adsorbed TPyP is about 0.1 V.) [13] In the experiment (Figure 1), [14,15] the sample, an adsorbed monolayer of TPyP on Au(111) without TPyP molecules in the 0.1m H 2 SO 4 solution, was initially held at a potential (E 1 = À0.1 V) where all the TPyP molecules were reduced. [13] A short oxidation potential pulse (E 2 , for duration t) was applied to the sample during STM imaging.…”

Comparative STM studies on island equilibrium shapes, shape fluctuations and island coalescence on Au(001) electrodes in chloric and sulfuric acid solutions

“…The reason lies in the presence of the liquid, the ions contained in the electrolyte and their interaction with the solid via direct chemical interactions, adsorption phenomena and charge transfer between the solid and the liquid. To date there is only few people who dedicated their scientific focus to atom migration at the solid liquid interface and to the quantitative analysis and the understanding of diffusion processes on solid surfaces in contact with a liquid [3][4][5][6][7][8][9][10][11][12][13][14][15].…”

“…Quantitative studies on atomic motion on metal surfaces in electrolyte cover investigations on equilibrium fluctuations of isolated steps [3,[16][17][18][19][20], the decay of clusters on metal electrodes [5,6,[13][14][15][21][22][23], island shape and shape fluctuation analyses [20,22,[24][25][26] and single-atom diffusion studies [4,11,12]. In all these studies, relevant surface migration processes were identified and the respective activation barriers were 0013 measured.…”

Amine‐Directed Hydrogen‐Bonded Two‐Dimensional Supramolecular Structures

“…Running STM experiments in an electrochemical environment enables the use of surface potential as an extra controlling parameter to provide a negatively charged Au(111) surface to facilitate the adsorption of the triaminobenzenium cations with apositive charge on the ring carbon (Scheme , structure III) and to bring TAB molecules close enough together to form intermolecular amine‐amine hydrogen bonds. The large scale STM image (Figure ) shows that adsorbed TAB molecules form a long range ordered monolayer on Au(111) along with gold islands (bright white features) which appear due to lifting of the gold reconstruction …”