Rotating disk electrode electrochemical

Zeng and Bruckenstein [383] have studied UPD of Cu at polycrystalline gold in 0.1 M NH3 + 0.1 M NaCl04 electrolyte using the rotating disk electrode, electrochemical quartz crystal microbalance, and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The experiments have revealed that Cu(0) UPD occurs in the potential range —0.4 V <... 

C. Deslouis, C. Gabrielli, P. Sainte-Rose Fanchine, B. Tribollet, Electrohydrodynamical impedance on a rotating disk electrode, ]. Electrochem. Soc., 1982,129, pp.107-118. 

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. ... 

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. 

Schmidt TJ, Gasteiger HA, Behm RJ. 1999b. Rotating disk electrode measurements on a high-surface area Pt/Vulcan carbon fuel cell catalyst. J Electrochem Soc 146 1296-1304. 

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]. 

Two types of cell have been described. In Fig. 1 a cell with a rotating disk electrode is shown. Connections to a pH-stat and to the interface are indicated simultaneously with recording CMT measurements, the metal and reference electrode and a counter electrode (not shown in Fig. 1) can be connected to a potentiostat, so that electrochemical measurements can be recorded intermittently. The volume of solution in the cell is ca. 400 ml. What matters for safe and reliable conditions of measurement is that the disk electrode rotating at a speed of no less than 1000 rpm ensures efficient stirring, so that the effect of alkali formed at the corroding metal (or sometimes at the counter electrode located ca. 1 cm below and parallel to the metal electrode) is immediately sensed effectively by the glass electrode and also the effect of acid supplied from the autoburet is quickly detected. 

The absence of dimer radical cation formation by diphenyl selenide under the pulse radiolysis conditions is in contrast to bimolecular reactions believed to occur under electrochemical conditions/ In these experiments, a rotating disk electrode was used in combination with commutative voltammetry under anhydrous conditions. The results led to the conclusion that reversible one-electron oxidation is followed by disproportionation, then reaction of the resulting dication with diphenyl selenide or an external nucleophile, with the likely intermediacy of the dimer dication (Fig. 33). As expected, the dihydroxy selenane is formed when water is present. Based on the kinetics of the electrochemical reaction, the authors believe the diselenide dication, not the radical cation, to be the intermediate that reacts with the nucleophile. 

A precondition for an appropriate decision in the planning of a preparative electroorganic synthesis is sufficient information about the electrochemical reaction. As far as possible, knowledge about the influence of parameters such as temperature, solvent, pH value, and stirring rate should be included. Electroanalytical standard methods to acquire such data have been discussed in Chapter 1 cyclovoltammetry as an especially valuable tool and its combination with the rotating disk electrode method for additional knowledge. At... 

The basic assumption is that the rotating filter creates a laminar flow field that can be completely described mathematically. The thickness of the diffusion boundary layer (5) is calculated as a function of the rotational speed (to), viscosity, density, and diffusion coefficient (D). The thickness is expressed by the Levich equation, originally derived for electrochemical reactions occurring at a rotating disk electrode ... 

Additives can be consumed at the cathode by incorporation into the deposit and/or by electrochemical reaction at the cathode or anode. Consumption of coumarin in the deposition of nickel from a Watts-type solution has been studied extensively. Thus, in this section we discuss the consumption of coumarin, which is used as a leveler and partial brightener. In a series of papers (33, 36), Rogers and Taylor, described the effects of coumarin on the electrodeposition of nickel. They found that the coumarin concentration decreases linearly with time at —960 mV (versus SCE and 485 to 223 rpm at a rotating-disk electrode, for plating times of 8 to 75 min. A rotating-disk electrode was used to achieve a uniform and known rate of transport of additive to the cathode. Rogers and Taylor found that the rate of coumarin consumption is a function of coumarin bulk concentration. Figure 10.16 shows that the rate of consumption... 

More recently, the soundness of the electrochemical approach for the generation of PINO from HPI has been confirmed by using cyclic voltammetry at a rotating disk electrode. Anodic oxidation had been also employed for the generation of the aminoxyl radical from hydroxamic acids. ... 

Electrochemical oxidation of hydroquinone was investigated on a rotating disk electrode in a solution containing 0.01 M quinone and hydroquinone in 0.5 M H2so4 at 298 K. The following values of current density at different electrode potential values and RDE rotation rates were obtained ... 

When the current at a rotating disk electrode (RDE) depends partly on mass transport, the instantaneous state of the electrochemical system can be characterized by an implicit functional relationship such as ... 

The measurement of a molecular diffusion coefficient D by electrochemical techniques is generally done with a rotating disk electrode in the limiting diffusion current condition and application of the Levich s equation [8]. 

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