Disk electrodes surface

Drill a hole (3mm i.d.) through a PYC rod (8mm o.d., 4cm long) and insert the GC rod (diameter = 3 mm, length = 5 cm) so that it fits tightly in the PVC rod, resulting in a GC disk electrode (Fig. 4.1). Polish the GC disk electrode surface with successively finer grades of sandpaper and diamond pastes, and finally with 0.3 pm alumina. Clean ultrasonically for at least 15 min. 

Dispose an amount of cream on the tip, enough to cover the overall disk electrode surface... 

Figure 5.3 (A) Schematic of the rotating disk electrode (RDE) (B) solution flow pattern near the disk electrode surface (xis the coordinate direction perpendicular to the disk electrode surface, r is the coordinate direction parallel to the disk surface, and 0 is the coordinate direction of the electrode rotation, respectively).

Figure 5.9 Schematic procedure for a catalyst layer coating onto the glassy carhon disk electrode surface. ...

Under steady-state conditions, the rate of charge-transfer process at the disk electrode is equal to the rate of removal of R from the disk surface (According to the definition of N, there is no further reaction of R at the disk electrode and chemical decomposition of R in the electrolyte solution). Therefore, the mass balance on disk electrode surface (x = 0) can be expressed as ... 

In the situation where the formed H2O2 or HO2 on the disk electrode surface is disproportionated with a reaction rate constant of ki, and the reaction from O2 to H2O2 or HOJ is reversible with a backward reaction rate constant of k 2, the similar analysis as for that shown in Figure 6.6 can be carried out. The mechanism is schematically shown in Figure 6.8. The obtained relationships between and are as follows ... 

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.)...

A necessary step in conducting these measurements is preparation of the WE. A well-developed procedure for electrode preparation is described by Mayrhofer et al. [3]. A small amount of catalyst power (Pt- or Pt alloy-based catalyst) is first mixed ultrasonically with deionized water, followed by the addition of alcohol or isopropanol ( 1.0 ml alcohol to 5 mg catalyst) and 5 wt.% Nation ionomer solution (-1/40 volume ratio with the alcohol) to form a well-mixed catalyst ink. Then a small amount of catalyst ink is pipetted and coated onto a disk electrode surface such as GC or gold electrode, with a geometric area of 0.2-0.5 cm. The coated electrode is then left to air dry. The total catalyst loading on a GC electrode can be adjusted to 0.02-0.2 mg cm . ... 

Figure 13 shows the influence of Ag/AgCl probe position (i.e., readings at two distances from the electrode surface). Calculations were performed in the case of a weakly conductive electrolyte to highlight the influence of the position of the probe on the potential distribution. No significant difference was observed between the two measurements when the probe was withdrawn from the electrode surface, the sudden variation of the potential at the aluminum/copper interface was barely reduced in comparison with measurements performed on the disk electrode surface itself Moreover, it should be noticed that the amplitude of the potential variations was smaller when the electrode was far from the substrate. 

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. 

In such systems the researcher can electrochemically clean and precondition the metal electrode before each run to provide an identical surface for the anodic and the cathodic half-reactions as well as for the catalytic reaction between them. Use of a rotating disk electrode/ckatalyst also allows surface- and diffusion-controlled processes to be easily distin-guished. ... 

The constancy of the diffusion layer over the entire surface and thus the uniform current-density distribution are important features of rotating-disk electrodes. Electrodes of this kind are called electrodes with uniformly accessible surface. It is seen from the quantitative solution of the hydrodynamic problem (Levich, 1944) that for RDE to a first approximation... 

Bhzanac BB, Arenz M, Ross PN, Markovic NM. 2004b. Surface electrochemistry of CO on reconstructed gold single crystal surfaces studied by infrared reflection absorption spectroscopy and rotating disk electrode. J Am Chem Soc 126 10130-10141. 

Figure 8.12 Relationships between the catalytic properties and electronic structure of Pt3M alloys correlation between the specific activity for the oxygen reduction reaction measured experimentally by a rotating disk electrode on Pt3M surfaces in 0.1 M HCIO4 at 333 K and 1600 lev/min versus the li-band center position for (a) Pt-skin and (b) Pt-skeleton surfaces. (Reprinted with permission from Stamenkovic et al. [2007b]. Copyright 2007. Nature Pubhshing Group.)...

Paulus UA, Schmidt TJ, Gasteiger HA, Behm RJ. 2001. Oxygen reduction on a high-surface area Pt/Vulcan carbon catalyst A thin-film rotating ring-disk electrode study. J Electroanal Chem 495 134-145. 

Schmidt TJ, Gasteiger HA, Stab GD, Urban PM, Kolb DM, Behm RJ. 1998. Characterization of high-surface area electrocatalysts using a rotating disk electrode configuration. J Electrochem Soc 145 2354-2358. 

Figure 14.12 CO bulk electro-oxidation at PtRu alloys, (a, b) PcRui j /Ru(0001) (x = 0.07, 0.25, 0.47) surface alloys measured in a flow cell with a CO-saturated electrolyte, (c) Freshly sputtered Pto.sRuo.s bulk alloy in a rotating disk electrode setup (data from Gasteiger et al. [1995]), compared with a Pto.53Ruo,47/Ru((X)01) surface alloy.

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