Scanning tunneling microscopy metal electrode surfaces

The preparation of well-defined platinum single crystals for the electrochemical environment is discussed in Chapter 10. However, the stability of these arrangements is the main focus of this section. The LEED analysis of the emerged surfaces in UHV conditions is difficult [19,20] because of the water impurities and solids left on the metal surface after their evaporation in the main chamber. Thus, many potential control experiments (as scanning tunnel microscopy (STM) and surface enhanced x-ray spectroscopy (SEXRS)) have been conducted to gain reliable information on the electrode interface characteristics [21,22],... 

Refs. [i] Conway BE (1999) Electrochemical processes involving H adsorbed at metal electrode surfaces. In Wieckowski A (ed) Interfacial electrochemistry, theory, experiment, and applications. Marcel Dekker, New York, pp 131-150 [ii] Climent V, Gomez R, Orts JM, Rodes A, AldazA, Feliu JM (1999) Electrochemistry, spectroscopy, and scanning tunneling microscopy images of small single-crystal electrodes. In Wieckowski A (ed) Interfacial electrochemistry, theory, experiment, and applications. MarcelDekker, New York, pp 463-475 [Hi] Calvo E] (1986) Fundamentals. The basics of electrode reactions. In Bamford CH, Compton RG (eds) Comprehensive chemical kinetics, vol. 26. Elsevier, Amsterdam, pp 1-78... 

SECM involves the measurement of the current through an ultramicroelectrode (UME) (an electrode with a radius, a, of the order of a few nm to 25 (zm) when it is held or moved in a solution in the vicinity of a substrate. Substrates, which can be solid surfaces of different types (e.g., glass, metal, polymer, biological material) or liquids (e.g., mercury, immiscible oil), perturb the electrochemical response of the tip, and this perturbation provides information about the nature and properties of the substrate. The development of SECM depended on previous work on the use of ultramicroelectrodes in electrochemistry and the application of piezoelectric elements to position a tip, as in scanning tunneling microscopy (STM). Certain aspects of SECM behavior also have analogies in electrochemical thin-layer cells and arrays of interdigitated electrodes. 

Summary. The importance of flie electrode surface structure in electrochemistry is briefly described. Examples are given in which the structural information provided by scanning tunneling microscopy (STM) is of assistance in clarifying the electrochemical behavior. The importance of surface structure in the photoelectrochemical response of metals is illustrated by an STM application. Finally, the potentialities of newr scanning microprobe techniques suitable for mapping local photoelectrochemical properties of metal surfaces are briefly discussed. 

AIREs, SEIRAS spectra show marked enhancement of the infrared absorptions of adsorbed species, up to 40 x that expected on a smooth, bulk metal electrode. Thus, Sun and coworkers [106] investigated the adsorption of CO at thin Au films evaporated onto a hemispherical Si prism, and observed a 20x enhancement over that expected at a conventional electrode this increased by a further factor of two when the Au film electrode was flame-annealed to generate a highly ordered Au(lll) surface, observed using ex situ scanning tunneling microscopy (STM). 

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