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The partial differential equations describing the mass transfer to a rotating ring disk electrode (RRDE) have been solved by the orthogonal collocation technique. The two spatial dimensions (normal and radial) are discretized leaving a continuous dependence in time. There is a semi-infinite boundary condition in the direction normal to the electrode. The space in the radial direction is, however, bounded. Thus, polynomials with a weighting factor ofe -~, with ~ = 1 and ~ = 1, 2, or 3, which are orthogonal to each other in [0, ~], are used in the direction normal to the electrode whereas the "shifted" Jacobi polynomials, which are orthogonal to each other in [0, 1], are used in the radial direction. Two different boundary conditions at the disk are examined, namely, a constant potential in the limiting current region and a constant applied current. Results are presented for an electron transfer at the disk as well as at the ring. The transient and steady-state currents at the disk and the ring electrodes as well as the simulated collection efficiency are in excellent agreement with previous theoretical treatments.

An inductively coupled pulsed-plasma reactor was used to synthesize polyaniline thin films on several substrates positioned at various distances from the center of the radio frequency (RF) coil. The samples were characterized with Fourier transform infrared (FTIR), cyclic voltammetry, and microscopic techniques. Impedance spectroscopy was used to determine the electrical characteristics of three-layer structures with polyaniline as the middle layer between top and bottom metal electrodes. FTIR results indicated that the chemical composition and structure of the films were very dependent on the substrate's position with respect to the RF coil, there being considerably less aromatic character closer to the coil. The electrochemical behavior of the films in acidic electrolytes was similar to that of smallmolecule aniline oxidation products; the number of peaks in the cyclic voltammograms varied with the substrate. Scanning electron microscopy indicated that as the films became thicker, they developed nodules atop a somewhat smoother underlayer. Results from transmission electron microscopy and optical birefringence suggested that the films were not completely homogeneous. The impedance measurements were consistent with relatively rough films possibly containing pinholes.

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phenylene oxide) films prepared in aqueous medium, found an intense band at 1592 cm 1 of diphenoquinone structure (6). In aqueous medium, the film structure is not uniquely polymer. We have also detected an intense absorption band at 1585 cm 1 due to C~O stretch of diphenoquinone film from anodic oxidation of 2-6 dimethyl phenol in aqueous medium (7).In conclusion, the detection of the radical form from 2-6 disec-butyl phenol confirms the radical mechanism during anodic oxidation of phenols. This gives also a clear proof of the possibility of the MIRFTIRS methods in studying "in situ" the intermediate species produced at the interface electrode solution. ABSTRACTThe partial differential equations describing the mass transfer to a rotating ring disk electrode where the intermediate generated at the disk electrode is decomposed by chemical reaction in the solution have been solved by the orthogonal collocation technique. The two spatial dimensions (normal and radial) are discretized leaving a continuous dependence in time. The space in the normal direction is discretized by exponentially weighted polynomials, whereas the "shifted" Jacobi polynomials are used in the radial direction. Results are presented for an electron transfer at the disk and ring together with decomposition of the intermediate generated at the disk by first or second order kinetics. Two different boundary conditions at the disk are investigated, namely, a constant potential in the limiting current region and a constant applied current. The transient and steady-state currents at the disk and the ring electrodes, as well as the simulated collection efficiency, are in excellent agreement with previous theoretical treatments. This algorithm, however, is much more accurate and takes much less computer time as compared to other techniques. The working curves provided allow the determination of rate constants of homogeneous reactions from ring current-rotation rate data obtained from a rotating ring disk electrode~ ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.132.123.28 Downloaded on 2015-05-16 to IP