Rotating disk electrode studies

Gasteiger HA, Markovic NM, Ross PN. 1995. H2 and CO electrooxidation on well-characterized PL Ru, and Pt-Ru. 1. Rotating disk electrode studies of the pure gases including temperature effects. J Phys Chem 99 8290-8301. 

In a detailed rotating-disk electrode study of the characteristic currents were found to be under mixed control, showing kinetic as well as diffusional limitations [Ha3]. While for low HF concentrations (<1 M) kinetic limitations dominate, the regime of high HF concentrations (> 1 M) the currents become mainly diffusion controlled. However, none of the relevant currents (J1 to J4) obeys the Levich equation for any values of cF and pH studied [Etl, Ha3]. According to the Levich equation the electrochemical current at a rotating disk electrode is proportional to the square root of the rotation speed [Le6], Only for HF concentrations below 1 mol 1 1 and a fixed anodic potential of 2.2 V versus SCE the traditional Levich behavior has been reported [Cal 3]. 

Rotating-Disk Electrode, Study of the kinetics and mechanism of electrode processes under well-defined mass transport conditions is possible through use of methods of the rotating-disk electrode (RDE). The RDE consists of a disk of metal embedded in a cylindrical insulator (e.g., Teflon) holder (see Fig. 6.24). It is rotated about its center. Only the bottom end of the metal disk is exposed to the solution. 

Shuman, M.S., Collins, B.J., Fitzgerald, RJ. and Olson, D.L. (1983) Distribution of stability constants and dissociation rate constants among binding sites on estuarine copper-organic complexes rotated disk electrode studies and an affinity spectrum analysis of ion-selective electrode and photometric data. In Aquatic and Terrestrial Humic Materials (eds Christman, R.F. and Gjessing, E.T.). Ann Arbor Science, Ann Arbor, MI, pp. 349-370. 

Fluoride ions greatly increase the dissolution rate of aluminous minerals. Zutic and Stumm (1984) found that for their rotating disk electrode study of AI2O3 dissolution, the surface reaction was sufficiently rapid to be diffusion controlled at [F ] > 10 M. Pulfer et al. (1984) showed that the rate of dissolution of bayerite was increased by a factor of more than 100 in 10 M fluoride, compared to dissolution without fluoride in 1.0 Af KNO3. Pulfer et al. (1984) stated that the increase in rate was approximately second-order with respect to both [H ] and [F ] in the pH range of 4 to... 

For rotating disk electrode studies, the appropriate kinetic terms are added to the convective-diffusion equations. For ac techniques, the equations in Table 12.2.1 are solved for Co(0, t) and Cr(0, t) in a form obtained by convolution [equivalent to (10.2.14) and (10.2.15) for the appropriate case]. Substitution of the current expression, (10.2.3), then yields the final relationships. 

The redox pair of [Fe(CN)6] /[Fe(CN)6] is frequently used as a test system, e.g., in cyclic voltammetry (see Sect. II. 1.5.3) or rotating disk electrode studies, assuming an uncomplicated electrode reaction. However, as seen in Fig. II. 10.3, the characteristic cyclic voltammetric curves of [Fe(CN)6] ions are accompanied with a frequency decrease during reduction and an increase during oxidation. 

Figure 10.8 Correlation of overpotential of the HER at a current density of 20mAcm and the onset overpotential during rotating disk electrode studies. (Reproduced from Ref. [72] with kind permission from Elsevier.)...

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