Rotating disk electrode current-potential curves

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. 

Experimental results obtained at a rotating-disk electrode by Selman and Tobias (S10) indicate that this order-of-magnitude difference in the time of approach to the limiting current, between linear current increases, on the one hand, and the concentration-step method, on the other, is a general feature of forced-convection mass transfer. In these experiments the limiting current of ferricyanide reduction was generated by current ramps, as well as by potential scans. The apparent limiting current was taken to be the current value at the inflection point in the current-potential curve. 

FIGURE 1.10. Rotating disk electrode voltammetry. A + e B, with a concentration of A equal to C° and no B in the solution a Linearized concentration profiles —, at the plateau (vertical arrow in b), , at a less negative potential (horizontal arrow in b). b Current potential curve, c Concentrations of A and B at the electrode surface, d Logarithmic analysis of the current potential curve. 

Assume that the reaction ox + c <=> red at the planar electrode is diffusion controlled. Sketch and correlate the concentration profiles Cox =f(x), where x is the distance from the electrode surface to the bulk of the solution, with the shape of the current-potential curve for electrolysis carried out at (a) a stationary disk electrode and (b) a rotating disk electrode. Support your explanation by the equations. (Skompska)... 

A rotating disk electrode (RDE) [7] is used to study electrode reactions, because the mass transfer to and from the electrode can be treated theoretically by hydrodynamics. At the RDE, the solution flows toward the electrode surface as shown in Fig. 5.22, bringing the substances dissolved in it. The current-potential curve at the RDE is S-shaped and has a potential-independent limiting current region, as in Fig. 5.6. The limiting current (A) is expressed by Eq. (5.33), if it is controlled by mass transfer ... 

Fig. 18. Current-potential curve for a rotating (1000 rpm) n-GaAs-electrode in the dark in 6 M HCl with 0.76 mM Cu ". Dashed curves are the partial currents of anodic decomposition (] ) and of Cu -reduction (jrea), as determined by a rotating ring-disk electrode [93]...

As mentioned in Sec. 2.1, simple superposition of the respective current-potential curves for the two partial reactions does not always yield the curve obtained with a complete electroless bath. This is illustrated in Fig. 21 [126], in which the current-potential curve obtained with a complete electroless copper bath containing EDTA (curve 1) is compared with the curve obtained in solution in the absence of formaldehyde (curve 2) and with that obtained in solution in the absence of Cu(II) (curve 3). All three curves were recorded at room temperature with a copper disk electrode rotating at 2100 rpm, while scanning the potential in the positive direction... 

The cause of this effect of nickel ions was investigated voltammetrically with a gold-plated rotating platinum disk electrode [158]. The current-potential curves shown in Fig. 33 demonstrate that the anodic oxidation of the reducing agent... 

Fig. 7. Galvanodynamic cathodic current-potential curves at different rotation speeds of the disk electrode. These curves were used to study the Influence of mass transfer on aluminum deposition. (EL II/A 100°C scan rate 2.3 A/dm s).

Fig. 9 gives an example of how to determine the charge transfer current density. The plotted lines were evaluated according to the least squares method. The data were taken from the stationary potentiostatic current-potential curves at five different rotating electrode disk speeds. 

Curve (b) of Figure 4 shows the same silent system as curve (a) but now upon a contracted current scale, while curve (c) shows the effect of ultrasonic irradiation upon curve (b), scanned at the same rate and in the oxidation direction only. Note that curves (b) and (c) are on the same current scale, both taken from ref. 31. Ultrasound has produced a 10-fold increase in maximum current. The plateau shape shows a limiting current at the extreme of oxidation potential reflecting hydrodynamic control independent of the voltammetric sweep rate. (This shape is also seen in other voltammetric procedures, e.g. when using rotating disk electrodes or microelectrodes.) In Figure 4 curve (c) this limiting current is found to be inde-... 

Figure 2. (top) Current-potential curve for a rotating disk electrode (1600 rpm) under 1 bar H2 in... 

Potentiodynamic curves were constructed for the oxidizing processes of benzene, chlorobenzene and diohlorobenzene v/ith the help of rotating disk electrode. At the range of potentials from 1.20 to 1.45V these curves pass the maximum (at 55°C). At more positive potentials one can see a current slump on the curves this fact testifies to a hindering of electrooxidation process. 

Fig. 2 Current-potential curves for a mixture of pyrocatachol (1 mM) and o-benzoquinone (1 mM) on Pt and Bi/Pt rotating disk electrodes in 0.5 M HCIO4 with 1 mM Bi(CI04)j. Sweep rate 10 mV s . Rotation frequency (1) 12.5, (2) 25, (3) 50 and (4) 75 Hz. (Reproduced with permission from Ref [2].)...

Fig. n Current-potential curves for reduction of PhCH(N02)2 0 mM) on a Pt rotating disk electrode in 0.5 M HCIO4 curve (1) and Pt with adlayers of Bi,... 

Figure 8.4 shows the importance of the coordination mode around the metal ion for the electrochemical properties of the layer. In Fig. 8.4 the mediation of the Fe(II)/(III) oxidation is studied by using a rotating disk electrode. Initially a thin film of [Ru(bipy)2(PVP)5Cl] is used and with this coating the current potential curve I is obtained (see Fig. 8.4b). On photolysis of the coating and formation of the aquocomplex (according to Reaction 5) curve II is obtained. Rotating disk behavior very clearly shows that the redox potential of the modifying layer is of prime importance to the electrochemical properties of the modified electrode.

Figure 1.16. Cyclic voltammograms under N2 (A,C) and rotating ring-disk current-potential curves in aqueous air-saturated pH 7 buffers (B,D) of 2FeCu and 2Fe-only directly adsorbed on a graphite electrode (A,B) and as a 0.7% (mol) suspension in a 1-/rm-thick phosphadytilcholine film on the electrode surface (C.D). The rapid charge transfer within the films of adsorbed catalysts is supported by the linear dependence of the peak currents on the scan rate. The non-ideal shape of the peaks is due to cooperative behavior of the catalytic films as a whole. The Fe / and Cu / potentials are the same in the adsorbed catalysts (A) but separate when the catalysts are in the lipid film (C). Autooxidation of the catalyst-02 complex is the major source of ring-detectable byproducts (see below) and accounts for the potential-dependent selectivity of electrode-adsorbed catalysts (B). The measured collection efficiency of the ring electrode toward H2O2 in these experiments was 15%.

Silicon. The snrface of silicon immersed in fluoride media is of interest for semiconductor processing and production of porous silicon (Section 5.7) [541, 542, 549, 550]. A typical current-potential curve of p-Si in a flnoride electrolyte (0.975 MNH4CI + 0.025 MNH4F + 0.025 MHF, pH 2.8) measured at a rotating disk electrode at rotation rate of 3000 rpm and potential scanning speed of 5 mV s is shown in Fig. 7.29. The steep rise of the current density near... 

Figure 7.29. Typical current-potential curve of p-Si [(100) orientation, doping 10 cm" ] in dilute fluoride electrolyte (here 0.975 M NH4CI + 0.025 M NH4F + 0.025 M HF, i.e., fluoride concentration 0.05 M, pFI 2.8). Rotating disk electrode rotation rate 3000 rpm, potential scanning speed 5 mV s". Reprinted, by permission, from F. Ozanam, C. da Fonseca, A. V. Rao, and J.-N Chazalviel, Appl. Spectrosc. 51,519 (1997), p. 521, Fig. 1. Copyright 1997 Society for Applied Spectroscopy.

Figure 3.3 Current—potential curve recorded on a rotating disk glassy carbon electrode coated with 20wt %Pt/C catalyst, measured in O2-saturated 0.1 M HCIO4 at 30 °C. Potential scan rate 5 mV electrode rotating rate 1600 rpm. Catalyst loading 0.048 mgp, cm Ryan Baker, Jiujun Zhang, Unpublished data.

Figure 5.5 (A) Current-potential curves at different electrode rotating rates, recorded on a Pt disk electrode (0.196 cm ) using a potential scan rate of 5 mV s in Oa-saturated 0.5 M H2SO4 aqueous solution (B) the Levich plot (C) the Koutecky—Levich plots at different electrode potentials and (D) plot of E vs ln(/i<,o). The measurement was...

Figure 5.15 Koutecky-Levich plots at different electrode potentials. The current-potential curves recorded on the Co-N-S/C catalyst-coated GC disk electrode (0.28 cm ) at different electrode rotation rates in 02-saturated 3.0 M KOH solution. Potential scan rate 25 mV s and catalyst loading 7.06 x 10 g cm ...

As an example. Figure 6.10 shows the ORR current—potential curves at the disk electrode and their corresponding currents at the ring electrode, recorded at different electrode rotating rates, where the horizontal abscissa is the disk potential, and the upper vertical ordinate is the ring current and the lower vertical ordinate is the disk current. 

Figure 6.10 Current—potential curves at the disk electrode (below the x-axis in each figure) and the current at the ring electrode (Pt) (above the x-axis in each figure), recorded in Oa-saturated 1.0 mol dm KOH aqueous solution at different electrode-rotating rates. Disk electrode surface coated with a layer of (A) W2C/C, (B) Ag/C, (C) Ag-W2C/C, or (D) Pt/C. Potential scan rate 5 mV s ring potential fixed at 0.474 V vs Hg/HgO, and ring collection efficiency 20%. The insets present the Koutecky—Levich p ols of the disk electrode at different potentials. (For color version of this figure, the reader is referred to the online version of this book.)...

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