Rotation curve data reduction

The nanostructured Au and AuPt catalysts were found to exhibit electrocatalytic activity for ORR reaction. The cyclic voltammetric (CV) curves at Au/C catalyst reveal an oxidation-reduction wave of gold oxide at +200 mV in the alkaline (0.5 M KOH) electrolyte but little redox current in the acidic (0.5 M H2SO4) electrolyte. Under saturated with O2, the appearance of the cathodic wave is observed at -190 mV in the alkaline electrolyte and at +50 mV in the acidic electrolyte. This finding indicates that the Au catalyst is active toward O2 reduction in both electrolytes. From the Levich plots of the limiting current vs. rotating speed data, one can derive the electron transfer number (w). We obtained n = 3.1 for ORR in 0.5 M KOH electrolyte, and 2.9 for ORR in 0.5 M H2SO4 electrolyte. The intermittent n-value between 2 and 4 indicates that the electrocatalytic ORR at the Au/Ccatalyst likely involved mixed 2e and 4e reduction processes. 

The folding of each rotation curve (see Section II.D). This data reduction process is nontrivial, and different people have their own favored methods. 

Figure 7.14 (A) Current—potential curves for Co"HFPC adsorbed on a rotating graphite disk electrode at different rates of rotation as (marked on each curve), recorded in an air-saturated 0.1 M Na2S04 solution buffered to a pH 6. Temperature 20 °C. Potential scan rate 10 mV s (B) Koutecky—Levich plot, data from (B). The thinner solid line is calculated according to Levich theory for a 2-electron O2 reduction process. The thicker solid line and data points are the experimental data. Reprinted with permission from Ref. 47.

Figure 27 presents the polarization curves for oxygen reduction on carbon black promoted by different cobaltitesin alkaline solution. In these rotating disk-ring electrode experiments an extremely thin layer of a catalyst was applied to the pyrographite disk electrode. The analysis of the experimental data has shown that the O2 in the presence of the cobaltites is reduced mainly to water without the formation of hydrogen peroxide. 

Fig. 4.13 - Experimental data for the study of Fe(CN)5 /Fe(CN)6 couple in KCl (0.5 mol dm ). Cq = c r = 10mmoldm . Au electrode (a) I-E curves as a function of rotation rates, (b) vs plots (cu = 27t/) at a series of potentials, o reduction, x oxidation, (c) Tafel analysis of kinetic currents, i.e. the log of the inverse of the intercepts of (b) vs potential. uncorrected data. X data corrected for back reaction.

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