Electrodeposition potentiostatic deposition

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. 

Numerous metal and alloy coatings can be prepared by electrodeposition and are suitable for nano-plating technologies, including Ag, Au, Cd, Co, Cr, Cu, Fe, Ni, Pt, Sn, Zn, and most alloys of the listed metals [7], Either a fairly inert counter electrode, such as a Pt mesh, a carbon rod, or a plate of the metal to be plated are used. In the latter case, the zero valent metal of the anode is oxidized and dissolved at the same rate as metal ions are reduced a the working electrode. In this manner, the cations concentration of the electrolyte bath is continuously replenished. In industrial applications usually a galvanostatic is favored over a potentiostatic deposition technique. 

A non-enzymatic H2O2 sensor based on Prussian Blue (PB], also known as an artificial peroxidase, was accomplished by step-by-step electrodeposition of polyaniline on a glassy carbon electrode (GCE] modified with MWCNTs followed by potentiostatic deposition of PB [42]. By using PB instead of peroxidase, the linear calibration range could be improved and interference due to oxygen prevented. A non-enzymatic H2O2 sensor based on PANI-SWCNT electropolymerized in the ionic liquid (IL]... 

The described method for the determination of the specific surface of electrodeposited copper is applicable if some kind of a Faradaic cage is not formed on the surface of deposit, i.e., when the formed structure is open to the bulk of electrolyte solution in potentiostatic deposition. 

Yang C-C, Cheh HY (1995) Pulsed electrodeposition of copper/nickel multilayers on a rotating disk electrode B. Potentiostatic deposition. J Electrochem Soc 142 3040-3043... 

The electrodeposition process can either occur under potential (potentiostatic deposition) or current (galvanostatic deposition) control. In practice, the common approach is to control the deposition flux (current) in order to obtain the deposit with desired thickness and properties. The electrodeposition under galvanostatic control can be executed as either the constant current process or using some more complex currenttime function profile. In the latter case, the electrodeposition process is commonly called the pulse current deposition and it has been widely used in industrial and academic applications. The typical pulse current function has the simple on/off profile shown in Fig. 11. ... 

Prior to the elecfrodeposition the substrates were electrochemically activated by a cathodic potential sweep in [BMP] [TFSI] containing SiCl4. As a final step Si was electrodeposited potentiostatically at different potentials for l-5h. The process of Li ion insertion/deinsertion in the Si structure was studied by means of cyclic voltammetry (Figure 5.3.2), chronopotentiomenfry, and electrochemical quartz crystal microbalance in [BMP] [TFSI] ionic liquid containing Li ions. The surface morphology and composition of the Si deposit were investigated by SEM and EDX analysis. 

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. 

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. 

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. 

Traditionally, the electrochemical analysis of thin layers of electrodeposited nonequilibrium alloys has simply involved either galvanostatic or potentiostatic dissolution of the electrodeposit under conditions where passivation and/or replacement reactions can be avoided [194, 195]. A technique based on ALSY at a RDE has also become popular [196], To apply this technique, a thin layer (a 10 pm) of the alloy of interest is deposited on a suitable electrode in a solution containing the reducible ions of the alloy components. The plated electrode is then removed to a cell containing an electrolyte solution that is devoid of ions that can be reduced at the initial potential of the experiment, and the complete electrodeposit is anodically dissolved from the electrode surface using slow scan ALSV while the electrode is rotated. 

The multilayered Cu/Co systems discussed here can be grown as described next (6b). Electrolyte composition is based on a cobalt/copper ratio of 100 1 and consists of a solution of 0.34 M cobalt sulfate, 0.003 M copper sulfate, and 30g/L boric acid. The pH is fixed around 3.0, and there is no forced convection while deposition is carried out. The electrodeposition may usually be carried out potentiostatically at 45°C between —1.40 V versus SCE for the cobalt and —0.65 V versus SCE for the copper with an 3 cell potential interrupt between the cobalt-to-copper transition to avoid cobalt dissolution, which can occur when there is no interrupt. 

These features are absent when a surface is prepared by means of electrodeposition or electrodissolution. There is one environment and no local heating. The potentiostat makes it easy to control the size of deposits. Dissolution can be affected as easily as deposition. 

Nanocrystalline aluminum can be made in the employed ionic liquid without additives, see Chapter 8. The SEM micrograph of Figure 12.9 shows the surface morphology of a deposited aluminum layer obtained potentiostatically on mild steel at —0.75 V (vs. Al) for 2 h in the upper phase ofthe biphasic mixture [Pyi TfiN M AICI3 at 100 °C. Prior to Al electrodeposition, the electrode was anodically polarized at a potential of 1V (vs. Al) for 2 min. The deposited layer is dense, shining and adherent to the substrate with crystallites in the nanosize regime. 

The electrodeposition can be carried out at room temperature, but is more facile at 50 °C or higher due to the resistance of the passive film. Typically about 50-100 mV of overpotential vs. Li/Li+ is sufficient to obtain a deposit. It is important to limit this overpotential to < 150 mV because of the reductive instability of the ionic liquid at more negative potentials. It is advisable therefore to plate under potentiostatic conditions. The achievable current density is very much dependent on the temperature involved. At 50 °C a good deposit can be obtained at 1-1.5 mA cm-2. Initiation of a good uniform film is often achieved by depositing initially at lower current densities to allow the creation of the passive film before higher current densities are applied. 

Currently, work is being conducted on an in situ electrodeposition sampling device 20, 21, 22), It consists of a submersible, self-contained potentiostat, power supply, reference electrode, and working electrode. Metals are deposited on the 1-in. diameter, wax-impregnated, pyrolytic graphite working electrode 21, 22, 23) which can then be removed from the sampler at the surface and stored. The metal film can be either... 

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