Deposition potentiostatic

Hua et al. [71] carried out automated determination of total arsenic in seawater by flow constant-current stripping with gold fibre electrodes in which the sample was acidified and pentavalent arsenic was reduced to the trivalent form with iodide. The arsenic was then deposited potentiostatically for 4 min on a 25 xm gold fibre electrode, and subsequently stripped with constant current in 5 M hydrochloric acid. Cleaning and regeneration of the gold electrode were fully automated. 

Fig. 46). These multilayers were deposited potentiostatically from a single solution containing both Co and Cu ions with a Co Cu ratio of 100 1. The potential of the cathode was pulsed between — 1.40 V (versus SCE) for the cobalt deposition and —0.65 V (versus SCE) for the copper deposition with an s cell potential interrupt between the Co-to-Cu... 

A standard three-electrode cell equipped with an Ag/AgCl reference electrode and a platinum mesh or stainless steel counter electrode was used for the metal electroplating. Before immersing the polystyrene templates into the plating solution they were dipped into methanol to enable the infiltration of the hydrophobic meso-pores by the aqueous electrolyte. Subsequently, the samples were rinsed with deionized water, dried, and electively freed from the styrenic template by dissolution in toluene for several minutes. Platinum metal was deposited potentiostatically at room... 

Electropolymerization. These monomers were anodically polymerized via repeated potential scanning on Pt button electrodes or deposited potentiostatically on ITO/glass at low potential to yield electrode confined films which are light blue. Table 1 lists some relevant properties of these materials. The onset is defined as the potential at which current starts to rise during the first scan of polymerization and low values are indicative of clean polymerization. As illustrated in Figure 2, this oxidation potential is ca. 250 mV... 

Fig. 24. Change of relative polymer film resistance of PANI deposited potentiostatically as a function of electrode [>otential (degree of oxidation) and of pH value of the electrolyte solution. For experimental detail, see [72, 309].

The poly(l-methylpyrrole) films and PEDOT films doped with 2-(V-morpholino) ethanesulfonic acid (PMPy-MES and PEDOT-MES films) were deposited potentiostatically from 0.4 or 1.33 M MES and 0.1 M MPy or 0.01 M EDOT solutions. The applied potential was equal to 750 mV for PMPy film deposition and 1050 mV for PEDOT film deposition, and the deposition time was (usually) equal to 600 s. 

ZnTe The electrodeposition of ZnTe was published quite recently [58]. The authors prepared a liquid that contained ZnGl2 and [EMIM]G1 in a molar ratio of 40 60. Propylene carbonate was used as a co-solvent, to provide melting points near room temperature, and 8-quinolinol was added to shift the reduction potential for Te to more negative values. Under certain potentiostatic conditions, stoichiometric deposition could be obtained. After thermal annealing, the band gap was determined by absorption spectroscopy to be 2.3 eV, in excellent agreement with ZnTe made by other methods. This study convincingly demonstrated that wide band gap semiconductors can be made from ionic liquids. 

Figure 2.3. Catalysis (0), classical promotion ( ), electrochemical promotion ( , ) and electrochemical promotion of a classically promoted (sodium doped) ( , ) Rh catalyst deposited on YSZ during NO reduction by CO in presence of gaseous 02.14 The Figure shows the temperature dependence of the catalytic rates and turnover frequencies of C02 (a) and N2 (b) formation under open-circuit (o.c.) conditions and upon application (via a potentiostat) of catalyst potential values, UWr, of+1 and -IV. Reprinted with permission from Elsevier Science.

Figure 11.8. Effect of po2 on the rate (TOF) of C2H4 oxidation on Rh supported on five supports of increasing d>. Catalyst loading 0.5wt%.22,27 Inset Electrochemical promotion of a Rh catalyst film deposited on YSZ Effect of potentiostatically imposed catalyst potential Uwr on the rate and TOF dependence on po2 at fixed Pc2H4-22,33 Reprinted with permission from Elsevier Science (ref. 27) and Academic Press (ref. 33).

Cu9ln4 and Cu2Se. They performed electrodeposition potentiostatically at room temperature on Ti or Ni rotating disk electrodes from acidic, citrate-buffered solutions. It was shown that the formation of crystalline definite compounds is correlated with a slow surface process, which induced a plateau on the polarization curves. The use of citrate ions was found to shift the copper deposition potential in the negative direction, lower the plateau current, and slow down the interfacial reactions. 

By electrodeposition of CuInSe2 thin films on glassy carbon disk substrates in acidic (pH 2) baths of cupric ions and sodium citrate, under potentiostatic conditions [176], it was established that the formation of tetragonal chalcopyrite CIS is entirely prevalent in the deposition potential interval -0.7 to -0.9 V vs. SCE. Through analysis of potentiostatic current transients, it was concluded that electrocrystallization of the compound proceeds according to a 3D progressive nucleation-growth model with diffusion control. 

Cathodic deposition of lead sulfide from acidic aqueous solutions of Pb(II) ions (nitrate salts mainly) and Na2S203 on various metallic substrates at room temperature has been reported. Stoichiometric PbS films composed of small crystallites (estimated XRD diameter 13 nm) of RS structure were obtained at constant potential on Ti [204]. Also, single-phase, polycrystalline thin films of RS PbS were electrode-posited potentiostatically on Ti, Al, and stainless steel (SS) [205]. It was found that the Al and Ti substrates promoted growth of PbS with prominent (200) and (111)... 

Within the scope of thermoelectric nanostructures, Sima et al. [161] prepared nanorod (fibril) and microtube (tubule) arrays of PbSei. , Tej by potentiostatic electrodeposition from nitric acid solutions of Pb(N03)2, H2Se03, and Te02, using a 30 fim thick polycarbonate track-etch membrane, with pores 100-2,000 nm in diameter, as template (Cu supported). After electrodeposition the polymer membrane was dissolved in CH2CI2. Solid rods were obtained in membranes with small pores, and hollow tubes in those with large pores. The formation of microtubes rather than nanorods in the larger pores was attributed to the higher deposition current. 

Electrodeposition of metals can be performed under different electrochemical modes. In the work mentioned in Ref. [18], it was performed in potentiostatic mode. The potential value for formation of platinum nanoparticles is —25 mV vs. SCE the deposition is performed from 2.5 mM solution of H2[PtCl6] in 50 mM KCl. The size of nanoparticles formed depends on the reduction charge. Continuous monitoring of the charge in potentiostatic mode is provided by different potentiostats, for example, by Autolab-PG-stat (EcoChemie, The Netherlands). Conditions for deposition of other metals should be selected according to their electrochemical properties. 

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