Electrochemical parallel electrode configuration

Marken and co-workers accomplished electrolysis without an intentionally added electrolyte by using a simple microflow electrochemical cell having a parallel electrode configuration [37]. Two electrodes are placed facing each other at a distance of the order of micrometers, and a substrate solution flows through the chamber. In this system, the liquid flow and the current flow are perpendicular. 

Figure 9.3 An electrochemical flow microreactor having a parallel electrode configuration.

Several cell configurations are common in electrochemical research and in industrial practice. The rotating disk electrode is frequently used in electrode kinetics and in mass-transport studies. A cell with plane parallel electrodes imbedded in insulating walls is a configuration used in research as well as in chemical synthesis. These are two examples of cells for which the current and potential distributions have been calculated over a wide range of operating parameters. Many of the principles governing current distribution are illustrated by these model systems. 

Figure 9 A simple T cell for tests in battery configuration. The two electrodes and the separator film are held in a parallel plate configuration [18]. (Reprinted with copyright from The Electrochemical Society Inc.)...

Fig. 6C Primary current distribution and potential profiles for a parallel-plate configuration, with the Luggin capillary placed close to the working electrode. K = 50 mS c/ r. Top equipotential lines. Bottom current lines. Reprinted with permission from Landau, Weinberg and Gileadi, J. Electrochem. Soc. 135, 396. Copyright 1988, the Electrochemical Society.

An important result of the theoretical description of the electrochemical patterns discussed above was that the distance between the working electrode and the equipotential surface has an important impact on the pattern formation, or more precisely, on the range of the spatial coupling. In view of this knowledge, it is to be expected that electrode configurations different from this parallel arrangement of two equipotential surfaces affect the dynamics in a different way. An experimental setup often employed in electrochemical experiments is the use of a Haber-Luggin... 

Electrochemical cells, be they for electrolysis to generate products or for producing electricity (e.g., batteries, fuel cells), fall into two broad categories with respect to the electrode configuration, monopolar and bipolar cells. In a monopolar cell, there are typically many anode and cathode assembUes that are electrically in parallel with each other. Thus, a monopolar cell is typically a high current cell compared to most bipolar cells. In the typical DC circuit configuration, monopolar cells are connected in series by intercell conductors. 

Marken and coworkers accomplished electrolysis without using intentionally added electrolyte using an electrochemical flow microreactor having a parallel plate-to-plate electrode configuration [19]. A substrate solution was introduced into the chamber, in which two electrodes were placed facing each other at a distance of micrometer order. In this system, the substrate solution flow and the current flow were perpendicular. 

There is another type of electrochemical flow microreactors that can be used for electrolyte-free electrolysis (Figure 9.5) [24]. In this system, two carbon fiber electrodes are separated by a spacer (porous PTFE membrane, pore size 3 pm, thickness 75 pm) at a distance of micrometer order. A substrate solution is introduced into the anodic chamber. The anodic solution flows through the spacer membrane into the cathodic chamber. The product solution leaves the system from the cathodic chamber. In this system, the electric current flow and the liquid flow are parallel. Using this electrochemical flow microreactor having a serial electrode configuration, the anodic methoxylation of p-methoxytoluene was accomplished effectively without intentionally added electrolyte. Protons generated by the anodic oxidation acted as carriers of the electricity. This process will be discussed in detail in the practical part of this chapter. The device could also be used for the anodic methoxylation of N-methoxycarbonyl pyrrolidine and acenaphthylene. 

Another interesting method of amperometric detection for LC is dualelectrode electrochemical detection. Instead of a single WE, one can place two WEs in series, parallel to or opposite each other. The series configuration is mostly used, mainly in the collection mode, i.e., the electroactive substance entering the detector is converted at the upstream (generator) electrode into a product that either is or is not detected at the downstream (indicator) electrode, depending on the potential of the latter. Hoogvliet et al.137,162 were easily able... 

Film electrodes can be conveniently prepared from numerous types of materials on a wide variety of substrates in a bewildering variety of configurations, with high purity and chemical and spatial reproducibility. Some applications rely on the convenience of preparing uniform electrochemical films on optical quality substrates for reflection spectrometry [2], or for electrodes in thin-layer cells, where flatness and parallelism of electrodes to tolerances of a few micrometers is necessary [3,4]. Film electrodes are useful for many other applications. In... 

Parallel-plate flow cells Most electrochemical flow cells are based on a parallel-plate electrode design with either horizontal or, more commonly, vertical electrodes in a monopolar or bipolar configuration (see Figure 26.12). With vertical electrodes, the cell is usually constructed in a plate-and-frame arrangement and mounted on a filter press. 

A number of electrochemical cell designs have been described but the most popular configurations are the three-electrode thin-layer cell and the wall-jet cell. Figure 5.21[20,102,166-171,189]. The eolumn eluent is introduced either parallel to... 

Several basic flow configurations in electrochemical reactors are depicted in Fig. 1. Flow through a porous layer, as would occur in a fuel cell, is shown in (a). Flow along a single plate and through two parallel plates is shown in (b) and (c). A rotating disk electrode is shown in (d). This ccaifiguration reduces mass transfer... 

Fig. 1 Flow configurations in electrochemical reactors (a) through a porous layer (white) upstream of an electrode (gray), (b) along a free plate, (c) through two parallel plates,...

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