Lead, underpotential deposition

Ragoisha GA, Bondarenko AS, Osipovich NP, Streltsov EA (2004) Potentiodynamic electrochemical impedance spectroscopy Lead underpotential deposition on tellurium. 1... 

For the case of surface truncation rods, the technique is based on the detection of diffraction peaks between Bragg peaks. Although this requires careful alignment and some a priori knowledge of the structure, monolayer sensitivity can be achieved. In fact, Samant et a/.138 have recently performed an in situ surface diffraction study of lead underpotentially deposited on silver employing this technique along with grazing incidence diffraction. It is clear that this technique will also find widespread use in the near future. 

Lead Underpotential Deposition on Silver Single Crystals... 

One may ask if these ideal faces actually exist. The evidence is that they do not exist even at thermal equilibrium there are disorders at the surface and more kinks are present than necessary for the average specified co. However, we shall see that this model does fit in with some experimental results of dl studies it explains other electrochemical results, such as lead underpotential deposition on gold faces. 

Having characterized the substrate, they then investigated the structure of a monolayer of lead underpotentially deposited on the silver(l 11) electrode surface. Figures 42a and b, respectively, show radial and azimuthal scans from a lead monolayer underpotentially deposited on a Ag(lll) electrode surface at a potential of —0.40 V vs. Ag/AgCl. That the diffraction arises from the lead monolayer was conclusively demonstrated by the fact that at an applied potential of 0.0 V vs. Ag/AgCl, where the monolayer is stripped, no diffraction peaks were observed (Fig. 42c). For the deposited monolayer, diffraction peaks spaced at 60° intervals were observed, consistent with the anticipated hexagonal lead overlayer. From these measurements, it was concluded that the electrodeposited lead forms a hexagonal monolayer that is incommensurate with the silver substrate and that at this potential, the Pb-Pb distance is 3.45 A. 

G. A. Ragoisha, A. S. Bondarenko, N. P. Osipovich, E. A. Streltsov, Potentiodynamic electrochemical impedance spectroscopy lead underpotential deposition on tellurium, J. Electro-anal. Chem., 2004i 565, pp. 227-234. 

Ivanov DK, Osipovich NP, Poznyak SK, Streltsov EA (2003) Electrochemical preparation of lead-doped amorphous Se films and underpotential deposition of lead onto these films. Surf Sci 532-535 1092-1097... 

Streltsov EA, Poznyak SK, Osipovich NP (2002) Photoinduced and dark underpotential deposition of lead on selenium. 1 Electroanal Chem 518 103-114... 

An alternative type of tip-induced nanostructuring has recently been proposed. In this method, a single-crystal surface covered by an underpotential-deposited mono-layer is scanned at a close tip-substrate distance in a certain surface area. This appears to lead to the incorporation of UPD atoms into the substrate lattice, yielding a localized alloy. This procedure works for Cu clusters on Pt(l 11), Pt(lOO), Au(l 11), and for some other systems, but a model for this type of nanostructuring has not been available until now. (Xiao et al., 2003). 

Hoshi N, Bae IT, Scherson DA. 2000. In situ infrared reflection absorption spectroscopic studies of coadsorption of CO with underpotential-deposited lead on Pt(lll) in an aqueous acidic solution. J Phys Chem B 104 6049-6052. 

Grgur BN, Markovic NM, Ross PN. 1997. Underpotential deposition of lead on Pt(lll) in perchloric acid solution RRDpt(in)E measurements. Langmuir 13 6370-6374. 

Melroy and co-workers88 recently reported on the EXAFS spectrum of Pb underpotentially deposited on silver (111). In this case, no Pb/Ag scattering was observed and this was ascribed to the large Debye-Waller factor for the lead as well as to the presence of an incommensurate layer. However, data analysis as well as comparison of the edge region of spectra for the underpotentially deposited lead, lead foil, lead acetate, and lead oxide indicated the presence of oxygen from either water or acetate (from electrolyte) as a backscatterer. 

Figure 2. Voltammograms for the underpotential deposition of lead on silver single crystal surfaces.

The authors acknowledge very helpful discussions with Dr. R. Adzic of the Institute of Electrochemistry, Belgrade, concerning the underpotential deposition of lead on single crystal silver substrates after chemical polishing. The authors also acknowledge support of the research by the U.S. Office of Naval Research. 

Effect of Underpotentially Deposited Lead on the Surface-Enhanced Raman Scattering of Interfacial Water at Silver Electrode Surfaces... 

CORIA-GARCIA PEMBERTON Effect of Underpotentially Deposited Lead 399... 

Electrodeposition and Underpotential Deposition of Lead on Solid Substrates... 

Pb Lead, and particularly underpotentially deposited Pb, exhibits electrocatalytic properties in numerous electrode processes. The model reaction can be oxygen reduction with slow step of peroxide reduction ]374-376] or reduction of nitrobenzene and other nitrocompounds [377, 378]. In the case of... 

The importance of electronic interaction as the basic mechanism leading to synergetic effects is also suggested by results showing that the simultaneous underpotential deposition of Cd and Tl on Ag(lll) results in an enhancement of the hydrogen evolution rate while inhibitory effects are shown by the two kinds of adatoms separately [317]. 

With increasing amounts ofbenzoic acid (0 to 0.38 wt.%) we observe a decreasing peak current for the aluminum deposition (see Figure 8.7), the aluminum oxidation peak disappears and the underpotential deposition (UPD) of aluminum is also strongly diminished. These experiments lead to the conclusion that the additive molecules block the active growth sites and therefore the peak current of aluminum deposition increases with decreasing additive concentration. A further consequence... 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

Lead adatoms were deposited on the platinum at controlled potential, under conditions of underpotential deposition leading to the adsorption of fractions of monolayer (9-11). 

The Cat, or its product of electrode oxidation or reduction Cat, is immobilized at the electrode surface and decreases the overpotential for oxidation or reduction of the S, without being involved in the chemical redox reaction with the S. Typical example is the catalytic effect of underpotential deposited layer of lead on a platinum electrode, on anodic oxidation of methanol [v]. 

An interesting aspect of UPD (underpotential deposition), which may be of great practical importance, is its effect on electrocatalysis. Studies of the oxidation of organic molecules on platinum have shown a significant catalytic effect, caused by a UPD layer of lead, as shown in... 

Fig. 61 Underpotential deposition of lead on gold from a solution of 1.0 mM Pb ClO ) in 1.0 MllClO. v = 10 mV/sec. Two underpotential (UPD) deposition and dissolution peaks are shown. Data from Deakin and Melroy, J. Electroanal. Chem. 239, 321 1988).

T vo different approaches have been made to increase the maximum deposition rate which is reached under a given set of deposition conditions. The first approach involves addition of a depolarizer, such as lead or thallium ions [162-164]. These ions are known to adsorb strongly on gold and to bring about underpotential deposition (UPD) during electrodeposition of gold [165]. The depolarization effect amounts to as much as 0.2 V, as reported by Matsuoka et al. [164] and illustrated in Fig. 34. These authors show that addition of such depolarizers to a borohydride bath increases the deposition rate by a factor of as much as 8 to 10 (Fig. 35). 

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