Electrodeposition electrochemical impedance

The UPD and anodic oxidation of Pb monolayers on tellurium was investigated also in acidic aqueous solutions of Pb(II) cations and various concentrations of halides (iodide, bromide, and chloride) [103]. The Te substrate was a 0.5 xm film electrodeposited in a previous step on polycrystalline Au from an acidic Te02 solution. Particular information on the time-frequency-potential variance of the electrochemical process was obtained by potentiodynamic electrochemical impedance spectroscopy (PDEIS), as it was difficult to apply stationary techniques for accurate characterization, due to a tendency to chemical interaction between the Pb adatoms and the substrate on a time scale of minutes. The impedance... 

As suggested by Epelboin et al. [72] on the basis of electrochemical impedance measurements, Ni [ds may play more than one role in Ni electrodeposition, and by extension, similar roles in electroless deposition. It is worth briefly noting the reactions Epelboin et al. proposed in which a Ni [ds intermediate may be involved in ... 

Electrodeposition on transparent material such as indium tin oxide (ITO) can be used for electrochromic applications [328]. Pb deposition on indium-tin oxide electrode occurs by three-dimensional nucle-ation with a diffusion-controlled growth step for instantaneous nucleation [329], and the electrode process has also been studied using electrochemical impedance spectroscopy [328]. 

Much information for the electrodeposition control is available in situ from analysis of AC response at controllable potential, especially with multi-frequency low amplitude perturbation overlaid on bidirectional potential scans. The latter technique, potentiodynamic electrochemical impedance spectroscopy. 

Another mechanism for induced codeposition of Mo was suggested by Chassaing et al for electrodeposition of Mo-Ni alloys from citrate-ammonia electrolytes. Electrochemical impedance spectroscopy (EIS) measurements were carried out in order to better understand the different reactions occurring on the electrode surface during deposition. The proposed mechanism is based on a multi-step reduction of molybdate species. A M0O2 layer is formed via reduction of molybdate ion as in Eq. (42). Then, if free Ni is present in solution, this oxide can first combine at low polarization with Ni, following the reduction reaction ... 

Cadmium atomic layer electrodeposition above reversible Cd2+/Cd potential (underpotential deposition, upd) on bulk tellurium and Te atomic layer predeposited on gold has been characterised with potentiodynamic electrochemical impedance spectroscopy (PDEIS) by variations, with the electrode potential E, of double layer pseudocapacitance Q,u, charge transfer resistance Rrt and Warburg coefficient Aw of diffusion impedance. 

Electrochemical impedance spectroscopy (EIS), also known as AC impedance spectroscopy, is a very powerful technique for characterizing the behaviors of electrode-electrolyte interfaces. Initially, EIS was used to determine doublelayer capacity subsequently, it has been used for more complicated processes, such as metal corrosion [21-24] and electrodeposition [25-27], and to characterize the electrical properties of materials and interfaces. With the developments in PEM fuel cells during recent years, EIS has been widely used for PEM fuel cell diagnosis and the electrochemical characterization of PEM fuel cell materials and components [17,28-35]. 

The results of electrochemical impedance spectroscopy show that Al coating leads to an increase in the polarization resistance of a bare Mg alloy by one order of magnitude in 3.5 wt% NaCl solution. Furthermore, the potentiodynamic polarization results show that Al-coated Mg alloy can be passivated, and a wider passive region with a lower passive current density can be obtained if the Al is electrodeposited at a lower applied current or a low cathodic overpotential. The passivity of the co-deposited Al/Zn film is slightly inferior to that of the pure Al coating. 

The Electrochemical impedance spectroscopy (EIS) results for the Mg alloy without and with surface Al coated from the 53 m/o and the 60 m/o ionic liquid, respectively, are depicted in Fig. 14.10. For bare Mg alloy, the polarization resistance was about 470 Qcm. A substantial increase in the polarization resistance, as evidenced by an enlarged diameter of the semicircle of the Nyquist plot, can be obtained for Mg alloy if it is electroplated with Al. For those with surface Al electrodeposited at -0.2 V from the 53 m/o and the 60 m/o ionic liquid, the polarization resistance in 3.5 wt% NaCl solution are 3000 and 5200 Qcm, respectively. The results were consistent with those revealed in the polarization curves demonstrated in Fig. 14.8. The improved polarization resistance of AZ91D Mg alloy with Al coating from ionic liquid is clearly demonstrated. However, the passivity or the polarization resistance of the Al-coated Mg alloy depends on the deposition conditions. The Al film formed in more acidic AICI3-EMIC and at a lower deposition rate renders a better passivation behavior. 

Krstajic et al. [31 ] investigated the corrosion behavior of polypyrrole electrodeposited mild steel in 0.1 M sulfuric acid by electrochemical impedance spectroscopy. They concluded polypyrrole did not provide anodic protection of mild steel. However, reduced polypyrrole lowered the corrosion velocity of mild steel by about a factor of 20. The total impedance increased with exposure time after an initial period. 

The most reported application of eiectrodeposited silane sol-gel films has been the corrosion protection of metals. The corrosion resistance of the films is usually evaluated by polarization curves and electrochemical impedance spectroscopy (EIS) measured in corrosive media. Mandler and coworkers [73] reported the electrodeposition of TEOS, MTMS, and PhTMS films on aluminum alloys. They found that all the three eiectrodeposited silane films protected the aluminum alloys, and the PhTMS film provided the highest corrosion resistance due to its hydrophobic aromatic ring. Figure 12.20 shows that the eiectrodeposited PhTMS film performs five orders of magnitude higher in impedance modulus... 

Ethanol electro- oxidation/cyclic voltammetry, electrochemical impedance spectroscopy Pt and Pt/Ru NaOH solution Electrodeposition of noble metal on CuNi alloys Higher electrocatalytic activity is found for ethanol oxidation for the catalyst layer prepared from PTFE suspension of noble metal salts rather without PTFE suspension. The charge transfer resistance is greatly reduced in the Pt/Ru-modilied CuNi electrodes Gupta et al. (2004)... 

Atomic force microscopy (AFM) and electrochemical atomic force microscopy (ECAFM) have proven usefiil for the study of nucleation and growth of electrodeposited CP films on A1 alloy [59]. AFM was used to study adhesion between polypyrrole and mild steel [60], whereas electric force microscopy (EFM) has been used to study local variations in the surface potential (work function) of CP films [61]. AFM with a conductive tip permits a nanoscale AC impedance measurement of polymer and electrolyte interfaces, permitting differentiation between highly conductive amorphous regions and less-conductive crystalline regions of the CP film [62]. 

There are only a few studies on the electrochemical behaviour of rhenium in molten salts [1-6]. Most investigations dealt with electrodeposition of rhenium and its alloys. The absence of reliable data on the electrochemical reduction of rhenium in molten salts greatly impedes further progress in the field of rhenium galvanoplastics and hinders interpretation of the experimental results. 

To introduce additional functionality and to allow for a wider variety of structural features, branching of the primary CNF/CNT with secondary, usually thirmer ones, has been performed [113,114]. Primary as well as secondary carbon nanostructures were grown in CVD processes. After electrodepositing iron as growth catalyst and subsequent CNT growth, secondary CNTs were grown in a similar fashion to yield hierarchically structured layers. The principles of such an approach are visualized in Figure 10.22. It was shown with impedance spectroscopy and other techniques, that the electrochemical properties of such composites are superior to those of unbranched CNF. 

In addition to chemical and electrochemical synthesis, other polymerization methods such as photochemical synthesis, emulsion, and pyrolysis have been reported [58, 63]. In a recent study, a self-assembled monolayers (SAMs) method has been used to deposit thiolated poly(alkylthiophene)s and functionalized alka-nethiols [82]. The authors claimed that resulting polymers have low impedance at 1 kHz and are more robust and better controlled in their composition than existing electrodeposited conductive polymer coatings. 

Burke, L. D. Shama, R. AC impedance investigation of copper in acid solution. 11. Effect of bath additives on copper electrodeposition. J. Electrochem. Soc. 2008, 155, D285-D297. 

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