Ferricyanide reduction rotating disk

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. 

The reaction may be characterized by slow surface kinetics, leading to shortening of the plateau. Compare, for example, ferricyanide reduction and copper deposition at a rotating disk (shown in Fig. 3a and b). 

Table 3.5 Standard deviations reported by Orazem et al. for their impedance data obtained for the reduction of ferricyanide on a Pt rotating disk electrode. The methods of Agarwal et a 56,86 yjgjj tQ fjitgr p jnor lack of replicacy from 26 repeated impedance experiments.

Figure 3.12 Ratio of the variance of the real part of the impedance to the variance of the imaginary part of the impedance for the data for the reduction of ferricyanide on a Pt rotating disk electrode. Dashed lines represent the F-value corresponding to 0.05 significance level and its inverse.

Figure 20.3 Comparison in Bode format of the model presented in Figure 20.1 to impedance data obtained for reduction of ferricyanide on a Pt rotating disk electrode a) modulus and b) phase angle.

Figure 18.1 Impedance data as a function of frequency for reduction of ferricyanide on a rotating Pt disk electrode with rotation speed as a parameter a) raw data and b) scaled data. (Taken from Durbha et al. )...

Figure 18.2 Impedance data from Figure 18,1 as a function of scaled frequency p = co/Cl for reduction of ferricyanide on a rotating Pt disk electrode a) the real part of the impedance and b) the imaginary part of the impedance.

When envisioning a family of impedance measurements, three measurement time scales become evident. The first time scale is that required for measuring a set of replicated measurements. Such a set of meeisurements is shown in Figure 21.5 for reduction of ferricyanide on a rotating Pt disk electrode. The time required for the set of three measurements was 3581 s (1 h). 

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