Anion adlayer

Magnussen, O.M. (2002) Ordered Anion Adlayers on Metal Electrode Surfaces. Chemical Reviews, 102, 679-725. 

Magnussen OM. 2002. Ordered anion adlayers on metal electrode surfaces. Chem Rev 102 679-725. 

The stmcture and coverage of anion adlayers close-packed adlayers usually cause a complete inhibition. 

Adzic RR, Wang JX. 2000. Structure and inhibition effects of anion adlayers during the course of O2 reduction. Electrochim Acta 45 4203-4210. 

Figure 5.10 STM images of ordered anionic adlayers. (a) PdCI42 ...

These experimental results demonstrate that the specific adsorption of anions leads to a significant decrease in junction stability, as illustrated in particular in the potential regions of disordered anion adsorption, as well as in the fluctuations in the plateau currents at potentials of the 2D-ordered anion adlayers. The instability of the conductance plateaus were statistically analyzed, by determining the standard... 

UPD of various metals on different gold surfaces is one of the most intensively studied subjects. Abruna and coworkers have reviewed [380] the UPD deposition at single-crystal surfaces of Au, Pt, Ag, and other materials. More recently, Mag-nussen [381] has described ordered anion adlayers on metal electrode surface, which can affect the UPD process. 

The adsorption of anions on metal electrodes has been one of the major topics in surface electrochemistry. Specific adsorption of anions occurs when the anion loses aU or part of its solvation shell and forms a direct chemical bond with the substrate. In this situation the surface coverage by anions can be high and the adlayer tends to form a close-packed structure that depends critically on the surface atomic geometry of the underlying substrate and the balance between the anion-metal and anion-anion interaction energies. The structures of halide anions adsorbed onto Au(Jtkl), Ag(hkl), and Pt(hkl) low-index surfaces have been the most widely studied systems by SXS, and a comprehensive review of ordered anion adlayers on metal electrodes is given by Magnussen [57]. 

Introduction Anions have a strong tendency to adsorb specifically at metal surfaces, for example, to estabKsh a direct bond with the electrode by partial loss of their hydration shell. As a consequence of the contact with the electrode, the ionic character of the anions is markedly reduced, resulting in a higher surface concentration than in case of nonspecific adsorption. This effect was first observed in double-layer studies on mercury [229, 230] and later confirmed and studied in detail on single-crystal solid electrodes [231-234]. Specifically adsorbed anions can form various types of ordered structures, either more open (cf. sulfate on Au(hld) [235, 236]) or close-packed as reported for halides on different solid electrodes [21]. Cyclic current-potential curves often reveal sharp current peaks, indicative of phase transitions within the anionic adlayers and hence of the existence of ordered phases [21, 237]. Thermodynamic data of specific anion adsorption was obtained in surface tension studies (on mercury only [229,238-240]), capacitance measurements [231-233], cyclic voltammetry, and chronocoulometry [234]. As an... 

The combination of classical electrochemical measurements with ex situ transfer experiments into UHV [242], and in situ structure-sensitive studies such as electroreflectance [25], Raman and infrared (IR)-spectroscopies [29, 243], and more recently STM and SXS [39] provided detailed knowledge on energetic, electronic and structural aspects of (ordered) anion adsorption and phase formation. These experimental studies have been complemented by various theoretical approaches (1) quantum model calculations to explore substrate-adsorbate interactions [244-246] (2) computer simulation techniques to analyze the ion and solvent distribution near the interface [247] (3) statistical models [67] and (4) MC simulations [38] to describe phase transitions in anionic adlayers. 

The following chapter is focused on the structure and phase behavior of specifically adsorbed anion adlayers on solid single-crystal metal electrodes. On the... 

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