Cathodes requirements

A 0.3619-g sample of tetrachloropicolinic acid, C6HNO2CI4, is dissolved in distilled water, transferred to a 1000-mL volumetric flask, and diluted to volume. An exhaustive controlled-potential electrolysis of a 10.00-mL portion of this solution at a spongy silver cathode requires 5.374 C of charge. What is the value of n for this reduction reaction ... 

Hydrogen Overpotential (Overvoltage) the displacement of the equilibrium (or steady-state) electrode potential of a cathode required for the discharge of hydrogen ions at a given rate per unit area of electrode. 

Many hollow cathode lamps are needed because each element, since it must be contained in the cathode, requires a different lamp. Some lamps, however, are multielement. The element analyzed must be contained in the cathode so that its line spectrum will be generated and absorbed by the same in the flame. 

Figure 1-14 shows a simplified layout for an SOFC-based APU. The air for reformer operation and cathode requirements is compressed in a single compressor and then split between the unit operations. The external water supply shown in figure 1-14 will most likely not be needed the anode recycle stream provides water. Unreacted anode tail gas is recuperated in a tail gas burner. Additional energy is available in a SOFC system from enthalpy recovery from tail gas effluent streams that are typically 400-600°C. Current thinking is that reformers for transportation fuel based SOFC APUs will be of the exothermic type (i.e. partial oxidation or autothermal reforming), as no viable steam reformers are available for such fuels. 

As noted above, the electrocarboxylation process has been widely investigated for the production of some NSAIDs, starting from parent arylethyl halides [6, 7]. On the other hand, the direct process at conventional cathodes requires quite negative potentials, and gives rise in some cases to moderate faradic efficiencies. Furthermore, attempts to scale-up the process in the case of the reduction of l-(3-phenoxyphenyl)-l-chloroethane [18] and l-(4-isobutylphenyl)-l-chloroethane [16] (which are the precursors of fenopren and ibuprofen, respectively) gave very different results with respect to those obtained in syntheses performed in bench-scale systems. In particular, passivation of the cathode surface was observed, and this resulted in lower yields and selectivities. Similar results were also observed during the electrocarboxylation of chloroacetonitrile [19]. 

Most probably, the successful conversion of substrates on BDD cathodes requires access to the diamond surface without spatial restrictions. Consequently, more sterically demanding substrates are not suitable. 

Such field emission cathodes require no heating, they are not inertial. These cathodes are stable against temperature fluctuations, and they possess a high density of field emission current and a high slope of current-voltage characteristics. The field emission cathodes based on carbon fibers have a sustained performance in conditions of technical vacuum ( 10 Pa). 

The extended red multialkali cathode and the GaAs and GaAsP cathodes require cooling. Coolers are often bulky and expensive, imposing constraints on the... 

The need for CO2 at the cathode requires some schemes that will either 1) transfer the CO2 from the anode exit gas to the cathode inlet gas ("CO2 transfer device"), 2) produce CO2 by combusting the anode exhaust gas, which is mixed directly with the cathode inlet gas, or 3) supply CO2 from an... 

As a matter of fact it has to be noted that one of the most fiivorable examples seen above, that is diacetone acrylamide polymerization onto Zn sheet cathodes, required the passage of 1 Faraday for obtaining 300 g of polymer coating on the basis of the reported in Table 3, this yield corresponds to a current efficiency of ss 20% only. 

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