Electrode adlayer structures

Akemann W, Friedrich KA, Stimming U. 2000. Potential-dependence of CO adlayer structures on Pt(l 11) electrodes in acid solution Evidence for a site selective charge transfer. J Chem Phys 113 6864-6874. 

Chang SC, Roth JD, Ho YH, Weaver MJ. 1990. New developments in electrochemical infrared-spectroscopy— Adlayer structures of carbon-monoxide on monocrystalline metal-electrodes. J Electron Spectrosc Relat Phenom 54 1185-1203. 

Fig. 16.14. Ordered structures of Cu layers on Au electrodes, (a) STM image of Cu adlayer on Au(lll). A y/ X y/ )R20° structure is observed. The Cu coverage is 0.33 monolayer, (b) Model of the adlayer structure, (c) STM image of Cu adlayer on Au(lOO). A quasihexagonal structure is observed, (d) Model of the adlayer structure (O - Au atoms in the topmost layer. - Cu adatoms). (Reproduced from Magnussen et al., 1990, with permission.)...

Zhang et al. [197] have studied adsorption of DL-homocysteine and L-homo-cysteine thiolactone on Au(lll) electrode in 0.1 M HCIO4 using CV and STM. Both compounds formed highly ordered adlayer on Au(lll). For both adlayers, structural models have been proposed. 

Shi et al. [68] have studied iodine adsorption on Ag using atomic-resolution electrochemical scanning turmehng microscopy (ECSTM) method. Distinctly different iodine adlayer structures and surface diffusion behavior were observed on mechanically polished pc-Ag in comparison with those obtained on single-crystal electrodes. 

Hanewinkel et al. [84] have studied the change in the surface resistance of an Ag(lOO) electrode caused by the adsorbed bromide. It was suggested that bromide ions adsorbed in the double layer of the hollow sites do not exchange electron with the metal. Shimooka et al. [85] have studied the adlayer structures of Cl and Br, and a growth of bulk AgBr layers on Ag(lOO) electrodes using in situ... 

Initial work examined structures formed on Cu h,k,l) surfaces in the acid electrochemical environment. Figure 2 shows adlayer structures formed on the Cu(100) [10] and Cu(llO) [11] electrode surfaces as imaged by in- situ atomic force microscopy. On the Cu(100) surface a (V2 x V2)R45° adlattice structure was observed at all but the... 

With the exception of the elegant mononucleation transients on silver deposition at defect-free silver electrodes [115, 156-159], the analysis of the macroscopic current, charge density, and/or capacitance transients does not provide direct access to structural information and molec-ular/atomistic mechanisms of 2D phase formation. Employing dynamic MC simulations of microscopic models, Rikvold and coworkers pointed out that mean-field rate equations, such as the ones based on the Avrami ansatz, are limited especially in the later stage of the overall transition [195]. For systems in which ordered phases are involved, the microscopic adlayer structure and the dynamic details of the adsorption, phase formation, and lateral diffusion processes should become important [196-198]. The combination of time-resolved dynamical MC simulations... 

Phase Transitions in Two-dimensional Adlayers at Electrode Surfaces 405 Tab. 2 Adlayer structures of halides on Au(hkl) and Ag(hkl), adapted from Ref [21]... 

Fig. 15 Cyclic voltammogram for Cu UPD on a well-ordered Au(lll) electrode in 0.1 M H2SO4 - -1 mM CUSO4, scan rate 1 mV (reproduced from L Kibler, Preparation and Characterization of Noble Metal Single-Crystal Electrodes. Copyright 2000 by International Society of Electrochemistry), and electrochemically derived Cu coverage (normalized charge referring to one complete Cu UPD ML) as a function of potentiai, determined by potential steps in the positive direction. The Cu adlayer structures are also shown (adapted from Ref [360]).

In the case of an Au(lOO) electrode, Wang and coworkers observed using SXS measurements that chloride formed uni-axially incommensurate c s/2 x p)i 45° adlayer structure on the Au(lOO) electrode surface and was compressed along the [100] direction when the potential became more positive [122]. A similar... 

Structural and electronic properties of electrode surfaces covered by foreign metal adlayers (usually with submonolayer coverage) are expected to be considerably different from either those of the substrate or the adsorbate hulk metals. The structure of the top surface layer will be that of the adlayer, determined by the substrate surface structure, adatom size and coverage, substrate-adsorbate interaction and in some systems, by interaction with coad-sorhed anions (see Section 3.2, Chapter 3 in this volume). Major advances in the understanding of metal adlayer structural behavior have heen achieved by recent applications of in situ scanning probes [3] and surface X-ray scattering techniques [4]. 

The results of the studies with singlecrystal electrodes [46-51] have demonstrated the existence of a structural dependence of the magnitude of the catalytic effects. The role of the adlayer structure in determining the observed dependence has not been clearly determined so far. In most studies, the adlayer... 

---