Rotating disk anode

Nanoparticle Size Control Using a Rotating Disk Anode for Plasma-Induced Cathodic Discharge Electrolysis... 

Figure 2.3.1 Schematic drawing of the principle of plasma-induced cathodic discharge electrolysis (a) and a rotating disk anode-type plasma-induced electrolysis cell (b)...

In this study, the authors improved the rotating disk anode type electrolytic cell so that the disk anode could be rotated at speeds higher than 3000 rpm. When the rotation speed of the disk anode is higher, removal of the particle formed in an early stage is quicker, which should decrease the particle growth. By using this improved cell, a Ni nanoparticle was formed, and the relations between the size of the formed nanoparticle and the electrolysis conditions such as the rotation speed of the disk anode and the electrolysis current were investigated. 

Figure 2.3.2 TEM image (a) and size distribution (b) of Ni nanoparticles formed by plasma-induced cathodic discharge electrolysis using the rotating disk anode-type electrolytic cell (1.0A, 100°C, 2000rpm)...

To semi-quantitatively understand the above tendency, a hydrodynamics description of the velocity of the melt film on the rotating disk anode was tried as follows. The molten electrolyte film on the rotating disk is transferred radially outward by centrifugal force. The fluid at the disk surface is replenished by continuously supplying the melt. Because of the symmetry of the system, it is convenient to write the hydrodynamic equations in terms of the cylindrical coordinates r, cp, and z, as shown in Figure 2.3.5. 

Tokushige, M., Nishikiori, T., and Ito, Y. (2010) Formation of Fine Ni Nanoparticle by Plasma-Indnced Cathodic Discharge Electrolysis Using Rotating Disk Anode. J. Electrochem. Soc., 157,10 162-166. 

By this discharge electrolysis, various particles have been formed, including Si, Ti, Fe, Co, Ni, Zr, Nb, Ta, Ag, Pt, and various alloys [9,10], To obtain finer and more uniform nanoparticles, a rotating disk anode-type electrolytic cell was constructed and its availability was examined. An outline of the cell is shown in Figure 7.1.17 [11]. 

Figure 7.1.18 Ni nanoparticles obtained by rotating disk anode-type cell. Electrolyte LiCI-KCl-CsCI temperature 400° C...

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. ... 

Square-wave anodic stripping voltammetry was employed by Komorsky-Lovric [107] for the determination of bismuth in seawater. A bare glassy-carbon rotating disk electrode was preconditioned at -0.8 V versus Ag/AgCl, prior to concentration of bismuth. The method was applied to seawater in the 12 ng/1 range. 

Shuman and Michael [326,327] introduced a technique that has sufficient sensitivity for kinetic measurement at very dilute solutions. It combines anodic scanning voltammetry with the rotating-disk electrode and provides a method for measuring kinetic dissociation rates in situ, along with a method for distinguishing labile and non-labile complexes kinetically, consistent with the way they are defined. 

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]. 

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. ... 

Lam, M.T., Chakrabarti, C.L., Cheng, J. and Pavski, V. (1997) Rotating disk electrode voltammetry/anodic stripping voltammetry for chemical speciation of lead and cadmium in freshwaters containing dissolved organic matter. Electroanalysis, 9, 1018-1029. 

The voltammetric oxidation of HOOH at a rotated-disk electrode yields a peaked anodic wave with a half-wave potential (Em) of + 2.1 V versus SCE. The maximum current (ilim) for HOOH oxidation at the rotated-disk electrode is directly proportional to the concentration of HOOH, and is consistent with a first-order diffusion-controlled process. 

Figure 3.13 Electrochemical oxidation of HOOH and reduction of its products at GC electrodes in MeCN (0.1 M TEAP) (a) linear-sweep anodic voltammograms for (A) 0, (B) 0.3, (C) 1.7, and (D) 3.3 mM HOOH (scan rate 2 V min-1 electrode area, 0.46 cm2) (b) rotated-ring electrode cathodic voltammogram (scan rate 10 mV s-1) of the product from the oxidation of 4 mM HOOH at the rotated-disk electrode (rotation rate 1600 rpm) for (A) ED disconnected, and (B) En = +2.6 V versus SCE (c) rotated-ring electrode cathodic voltammogram (scan rate 10 mV s-1) of the products from the oxidation of 1 mM HOOH at the rotated-disk electrode (rotation rate 4900 rpm) for (A) disconnected and (B) ED = +2.6 V versus SCE.

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