Polarization measurements galvanostatic

Steady-state galvanostatic polarization measurements were conducted on a series of aqueous solutions of organic compounds in contact with Pt-alloy-type gas diffusion electrodes under acidic conditions to characterize their electro-oxidation behavior. A number of potential fuels were studied, including dioxane, tetrahydrofuran, 1,2-dimethoxyethane, dimethoxymethane, trimethyl orthoformate, trioxane, and methanol, and prepared in dilute aqueous solutions of sulfuric acid and triflic acid. Many polarization measurements were in the... 

From the galvanostatic and chronopo-tentiometric polarization measurements... 

Figure 2. XRD patterns measured ex-situ from graphite particles and chronopotentiograms of graphite electrodes polarized galvanostatically from OCV to low potentials in CHj-OCH2CH2-OCF[2CF[2-OCF[ (diglymej/LiClO solution (a) and in PC/LiAsF solution (b). The letters near the V vs. capacity curves correspond to the relevant XRD patterns, which have been measured after different periods of galvanostatic polarizations. Notice that in the diglyme solution (a) the XRD patterns clearly indicate progressive destruction of the active mass, while in the PC solutions (b) the XRD patterns show that the active mass remains pure graphite.

D.A. Jones, The advantages of galvanostatic polarization resistance measurements. Corrosion 39 (1983) 444-448. 

For RBP, a logarithmic current density range of 2.5 to 6 mA/cm was used, as shown in Figure 7.13. Treated samples at 60,100, and 120 N are shown, whereas the other samples are not shown because of crowdedness in the figure. Potentiostatic polarization measurements were carried out using a Radiometer Analytical model PGZ 100 potentiostat/galvanostat with VoltaLab software. The electrochemical parameters—corrosion potential corrosion current... 

This proposed mechanism of the electrochromic process in nickel oxide electrodes is further supported by measurements of the expansion of the oxide host matrix during the activation process, obtained by determining the mechanical stress induced by ion intercalation [25,26]. For this experiment, galvanostatic polarization (using very low current densities, i.e. of a few pA cm", to avoid undesired side reactions like metal electrodeposition)... 

Galvanostatic and Potentiostatic Polarization Measurements. Electrode processes may be classified into two types reaction or charge-transfer controlled, and diffusion or mass-transfer controlled. The electrode processes in diaphragm and membrane chlor-alkali cells are charge-transfer controlled. On the other hand, the formation of sodium amalgam on a mercury cathode, is diffusion-controlled. 

Figure 6.39 Galvanostatic polarization of Ni in the transpassive potential region in sodium nitrate solution (a) anodic polarization curve in the transpassive potential region (b) the current efficiency for metal dissolution and (c) the apparent thickness of the film as measured by coulometry [36].

Hafezi H, Newman J (2000) Verification and analysis of transference number measurements by the galvanostatic polarization method. J Electrochem Soc 147(8) 3036-3042... 

Applying a constant current for a known time leads to a concentration gradient that is measured indirectly by observing the relaxation potential after current interruption [16]. Combining the galvanostatic polarization experiment, determination of salt diffusion coefficient and concentration dependence of the potential by emf measurements enables to calculate the cationic transference number [17]. 

Side reactions can introduce error into the measurement of physical properties in three ways [73]. Current is consumed by the side reaction, introducing error into calculations of the amount of current that went into the main reaction. Bulk concentrations of salt or solvent may change if the side reaction is substantial, and soluble products of reaction may affect the activity of the electrolyte. Finally, the side reaction causes the potential of the electrode to be a mixed (corrosion) potential. It is commonly assumed that the lithium electrode is covered by the SEI layer. However, there is strong evidence that, in many situations, the protection is not complete and side reactions involving the solvent or anion continuously occur. Such reactions can increase the concentration of lithium ions adjacent to a lithium electrode, introducing error into measurements of the variation in potential with apparent electrolyte concentration, particularly at low electrolyte concentrations. Such concentration-ceU measurements are used to obtain activity coefficients and transference numbers via the galvanostatic polarization method. Simulations of the type described in this section can be used to analyze how much error is introduced by the side reaction [73]. It may be preferable to use a less reactive reference electrode, such as Li4Ti50,2 [74], to reduce this error. 

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