Rotating ring-disk electrode collection efficiency

In a rotated ring-disk electrode experiment where the disk is controlled at +2.6 V versus SCE for the oxidation of HOOH and the ring electrode is controlled at -1.4 V versus SCE for the reduction of the oxidation products from HOOH, the observed collection efficiency (N = /r//d) is 0.384. This is slightly less than the theoretical value of 0.418 for the electrode. The products from HOOH oxidation at the glassy-carbon disk electrode (ED, + 2.6 V vs. SCE) can be characterized at the ring by scanning its potential from +1.0 to... 

Prater KB, Bard AJ (1970) Rotating ring-disk electrodes. 1. Fundamentals of the digital simulation approach. Disk and ring transients and collection efficiencies. J Electrochem Soc 117 207. 

Figure 3.14 Experimental collection efficiencies (Nexpti) at the rotated-ring electrode as a function of HOOH concentration for the product from the oxidation of HOOH at the rotated-disk electrode. Control conditions for GC ring-disk electrode rotation rate, 4900 ipm ED, +2.6 V versus SCE ER, +0.1 V versus SCE.

Pseudo-first-order rate constants, fci (normalized to unit substrate concentration IS]), were determined from current-collection-efficiency data (02 decay rates) with a glassy-carbon-glassy-carbon ring-disk electrode that was rotated at 900 rpm. (O2 was produced at the disk electrode from dissolved O2, which reacted with 2 mM substrate, and the unreacted O2 was determined by its oxidation at the ring electrode.)... 

Figure 9.5.4 Time dependence of the oxygen reduction current at the disk and the Cu(II) reduction current at the ring of a platinum ring-disk electrode. Solution 0.2 M H2SO4 and 2 X 10 M Cu(II) with air saturation. Rotation speed, 2500 rpm. Disk potential held at 0.00 V v. SCE for f > 0 ring potential = —0.25 V v. SCE at all t. Disk area, 0.458 cm = 0.36 collection efficiency, 0.183. [Reprinted with permission from...

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%.

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.)...

The collection efficiency depends on the geometric parameters of the ring and disk electrode arrangement. It is stable amongst the whole potential range and all the rotation rates for a smooth electrode. Typical values for N are between 20 % and 35 % for most of RRDE setups. 

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