Bipolar configuration

Figure 12.10. Multiple-channel electrochemical cell termed bipolar configuration of second generation. 1 Reprinted with permission from Elsevier Science.

In experiments at relaxation fields close to zero, the precision, resolution and stability of the absolute value of Br become critical and a bipolar configuration though it makes the design and implementation of the hardware more complex, it improves the precision of the whole system and offers the following advantages ... 

Precise null calibration of current offsets (which can be positive as well as negative) is possible thanks to the bipolar configuration of the power supply whose range in the negative section, is much smaller than in the positive section, and can be set with a considerably higher resolution. This increases the absolute precision of the field values for very small relaxation field settings and, in practice, makes it possible to extend the NMRD profiles to fields as low as a few tens of iT. 

Thanks to the bipolar configuration of the power supply, at least the static axial component ARgnv of the environmental magnetic field can be easily compensated by means of a small current offset A7 generating an axial field offset AR of the same value as ARgn, but of opposite sign. 

Water electrolyzer units typically consist of several cells or electrodes arranged in two basic configurations, tank type operated in unipolar configuration, or filter press type operated in bipolar configuration. Tbe most common configuration, see Fig. 2.1, is the unipolar tank type where each electrode has only one polarity and all the electrodes of the same polarity are connected in parallel. The anodes and cathodes are alternately connected, with the... 

There are two types of multielectrode reactor monopolar and bipolar cells, as shown in Fig. 15.2. The bipolar configuration has the advantage that the electrical circuit has only to be linked at the ends of the electrode pile the disadvantage is limitation to certain electrode materials when the anode and cathode are of the same material or when they can be easily glued to each other. 

Figure 3. Schematic of droplet configuration and PDLC device operation A) bipolar configuration, B) radial configuration.

Cells usually have a bipolar configuration. The electrocatalysts are bonded to each side of the membrane (15), and the resulting SPE is a structurally stable membrane-electrode assembly as shown in Figure 1. A multi-layer package of expanded metal screens which presses up against the electrode on one side serves as the current collector and fluid distributor. 

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. 

The only viable way to achieve electrochemical promotion in dispersed systems involves indirect bipolar polarization of the catalyst in a suitable electrochemical cell. Electrochemical promotion in bipolar configuration is feasible. This was first demonstrated by polarizing a platinum stripe catalyst deposited between two gold feeder electrodes, each on the same side of an YSZ plate. The promotion achieved in... 

The model was first verified for the case of a bipolar stack with fourteen Ni electrodes. " The electrochemical reaction used for the determination of current bypass was the electrolysis of water in alkaline solutions. Good agreement between experimental and estimated current bypass was observed, especially at high current densities. The model was adapted successfully for solid electrolyte cells of bipolar configuration, as discussed below in Section IV.2.i. 

As a first step in the development of new cell designs, ring-shaped electrochemical cells were prepared in our laboratory. This configuration, also termed bipolar configuration of the first generation, allows for experimental determination of the current bypass. Nearly bypass-free configurations have been realized. The feasibility of electrochemical promotion in such bipolar cells has been successfully demonstrated. 

The results clearly demonstrate the feasibility of electrochemical promotion with bipolar configurations of the first generation. 

As a second step towards achievement of efficient electrochemical promotion over dispersed catalysts, a multiple-channel electrochemical cell, termed bipolar configuration of the second generation, has been... 

One configuration employs two oppositely charged needles directed toward each other for droplets with opposing charges that attract each other and coagulate. Figure 22.13 is a schematic of this bipolar configuration. 

The most widely used design for high power applications is the bipolar configuration in a filter press design causing minimum losses due to electric resistances. The main components in the stack are... 

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