Electrodes, types

To develop a highly efficient AFC, an electrode stracture with more than one pore system or with a bimodal pore distribution is required. The liquid and gaseous reactants must reach the electrolyte that has direct contact with the anode and cathode catalysts. For AFCs, different electrode types have been used. The main types of electrodes are the PTFE-bonded GDE and the DSK. 

PTFE-bonded GDEs can be manufactured by different methods. One method is preparation under wet conditions (using inks or paste materials) followed by drying and tempering steps. Another method is dry preparation, which is described below. The dry method avoids the use of solvents and lowers the energy consumption because the drying steps are not required. The layers are often thicker when using the dry procedure than with the wet procedure [33]. 

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More recendy, two different types of nonglass pH electrodes have been described which have shown excellent pH-response behavior. In the neutral-carrier, ion-selective electrode type of potentiometric sensor, synthetic organic ionophores, selective for hydrogen ions, are immobilized in polymeric membranes (see Membrane technology) (9). These membranes are then used in more-or-less classical glass pH electrode configurations. 

The ABMA Commercial BW Requirements gives water condition guidelines for electrode-type boilers, both low voltage (LV) and high voltage (HV) ... 

Incorporation into a Polymer Layer In recent years a new electrode type is investigated which represents a layer of conducting polymer (such as polyaniline) into which a metal catalyst is incorporated by chemical or electrochemical deposition. In some cases the specific catalytic activity of the platinum crystallites incorporated into the polymer layer was found to be higher than that of ordinary dispersed platinum, probably because of special structural features of the platinum crystallites produced within the polymer matrix. A variant of this approach is that of incorporating the disperse catalyst directly into the surface layer of a solid polymer electrolyte. 

Cell type Electrode type Analyte ion activity Ref... 

Fig. 2.10. Membrane electrode types. 1 Glass electrode 2, 3 and 4 crystal membrane electrodes. 

It is beyond the scope of this chapter to discuss all devices in detail. The discussion is thus focused on the electrode type and material and separators. 

This last point is particularly important. With the previous electrode type the electrical connection to the cell body could be realised along its periphery only, resulting in a poor current distribution in instances of large electrode size. 

In the following section, examples of electrode materials for application as anode and/or as cathode, and then some electrode types of practical interest are discussed. A comprehensive overview... 

Examples of Electrode Types and their Special Properties... 

Table 7.1 Relationships between the limiting current and various convective parameters for a number of electrode types ...

The most common is the coloured electrode type, in which the transparent... 

Fig. 6 Cyclic voltammograms of a platinized platinum electrode (type II) in (a) 0.25 mol dm H2SO4, (b) 0.25 mol dm H2SO4 + 10 mol dm HNO3, and (c) 0.25 mol dm H2SO4 - -10 mol dm HNO3. Sweep rate,...

Panel (c) shows typical results for the pH of rainwater. The average of the 17 measurements is given by the horizontal line at pH 4.14 and the letters s, t, u, v, w, x, y, and z identify types of pH electrodes. Types s and w had relatively large systematic errors. The type s electrode was a combination electrode (Figure 15-9) containing a reference electrode liquid junction with an exceptionally large area. Electrode type w had a reference electrode filled with a gel. 

Type of Electrode Type of Construction Selective to Ions... 

About ten years ago, Bessman et al(10), University of Southern California, developed a glucose sensor of enzyme electrode type with glucose oxidase (G0X) for an artificial pancreas. This sensor had... 

Reference-electrode type Potential determining ion in solution... 

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