Homogeneous Mixed Electrodes

Fig. 2-5 Partial and total current densities in electrolytic corrosion of a homogeneous mixed electrode.

Electrode Preparation. Electrodes were prepared by mixing the samples with equal parts of pure graphite. To insure homogenous mixing and to determine the plate sensitivity, 50 ppm indium was added as an internal standard to the sample-graphite mixture. (In this paper, ppm are given in terms of weight.) The mixtures were pressed into... 

Standards define uniform surface corrosion as corrosion practically equal to mass loss over the entire surface (homogeneous mixed electrode), and nonuniform corrosion (shallow pit formation) as corrosion with locally different mass losses. 

Ultrasound brings about homogeneous mixing of the electrode products with the bulk solution, so that the reaction of electrons with ethanol is minimized since the Birch process is much faster. 

Electrochemical template-controlled sjmthesis of metallic nanoparticles consists of two steps (i) preparation of template and (ii) electrochemical reduction of metals. The template is prepared as a nano structured insulating mono-layer with homogeneously distributed planar molecules. This is a crucial step in the whole technology. The insulating monolayer has to possess perfect insulating properties while the template has to provide electron transfer between electrode and solution. Probably, the mixed nano-structured monolayer consisting of alkylthiol with cavities which are stabilized by the spreader-bar approach [19] is the only known system which meets these requirements. 

In order to understand the observed shift in oxidation potentials and the stabilization mechanism two possible explanations were forwarded by Kotz and Stucki [83], Either a direct electronic interaction of the two oxide components via formation of a common 4-band, involving possible charge transfer, gives rise to an electrode with new homogeneous properties or an indirect interaction between Ru and Ir sites and the electrolyte phase via surface dipoles creates improved surface properties. These two models will certainly be difficult to distinguish. As is demonstrated in Fig. 25, XPS valence band spectroscopy could give some evidence for the formation of a common 4-band in the mixed oxides prepared by reactive sputtering [83],... 

The results of the above mentioned study on mixed oxides prepared by thermal decomposition [84] are not in contradiction to the results obtained on reactively sputtered electrodes. A premise for common d-band formation is the formation of a solid solution with homogeneous properties which is probably not obtained during thermal decomposition. Indeed the authors find a trend towards the behaviour of the sputtered electrodes when homogeneity is improved by changing the solvent for the starting compounds. 

Stabilization of Ru based oxides by valve metal oxides has not been studied in such detail using photoelectron spectroscopy. The most common compositions, however, with relatively high valve metal content, are not in favor of formation of a solid solution. Studies of the phase formation in Ru/Ti mixed oxides has shown [49] that homogeneous solutions are formed for compositions with Ru < 2% or Ru > 98% (see Section 3.1.1). Therefore electrodes with other compositions are better described as physical mixtures and the electrochemical behaviour is most likely that of a linear superposition of the single components. It has to be considered, however, that the investigations performed by Triggs [49] concern thermodynamic equilibrium conditions. If, by means of the preparation procedure, thermodynamic equilibrium is... 

Fig. 3. Schematic illustration of the synthesis of metal nanoparticles within dendrimer templates. The composites are prepared by mixing of the dendrimer and metal ion, and subsequent chemical reduction. These materials can be immobilized on electrode surfaces where they serve as electrocatalysts or dissolved in essentially any solvent (after appropriate end-group functionalization) as homogeneous catalysts for hydrogenation and other reactions...

Figure 25. Adler s ID macrohomogeneous model for the impedance response of a porous mixed conducting electrode. Oxygen reduction is viewed as a homogeneous conversion of electronic to ionic current within the porous electrode matrix, occurring primarily within a distance A from the electrode/electrolyte interface (utilization region). (Adapted with permission from ref 28. Copyright 1998 Elsevier.)...

In related work, Dong and coworkers reported using the hydrophobic IL [C4CiIm][PFg] mixed with MWCNs to form two types of MEs [35,36]. In one report, MWCNs were mixed with [C4CiIm][PFJ and applied to a GC electrode [35]. Environmental scanning electron microscopy (ESEM) images of the films showed homogeneously dispersed island-like particles that open up into a number of rope-like 3-D networks. They incorporated GOx into... 

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