Electrode Teflon-bonded platinum black

The packaging approach utilized for tliis battery is similar to that for nickel—hydrogen single cylindrical cells as shown in Figure 23. The sdv er electrode is typically the sintered type used in rechargeable sdv er—zinc cells. The hydrogen electrode is a Teflon-bonded platinum black gas difhision electrode. 

A similar idea concerning the combination of charging curves and gas chromatography in the study of carbonaceous species on a Teflon-bonded platinum-black electrode was used in reference 60. The species were formed by adsorbing propane first and dehydrogenating the species afterwards. However, the amount of CO2 cannot be deteripined quantitatively since diffusion of CO2 into the electrolyte takes place. Only the amount of carbon dioxide that leaves the side of the electrode adjacent to the gas phase was determined. 

The difficulty of distinguishing between chemisorbed carbonaceous species is illustrated by the results of Niedrach [5] in Fig. 51. The electrode which consisted of Teflon-bonded platinum black was brought to U = 0AY. Different hydrocarbons were allowed to interact with the electrode at open circuit in 2.5M H2SO4 at 25 °C. When equilibrium... 

Practical units of fuel cells could not operate without porous electrode structures. Porous electrodes with their large electrochemically active surface allow reasonable currents to be supplied at acceptable losses due to polarization (see section 2 of chapter II). Although a few properties, like maximum available surface of electrocatalyst and hydrogenation and dehydrogenation of carbonaceous species for Teflon-bonded platinum black electrodes, and formation of oxygen layers for Raney nickel electrodes, have been discussed in preceding chapters, a discussion of the parameters that determine the operation of porous electrodes had to be offered in a separate chapter. While the empirical aspects concerning the operation of porous electrodes are covered in this chapter, theoretical aspects are dealt with in chapter XVI. 

Conditions a and b are not met by Teflon-bonded platinum black electrodes, so that a correlation between Ag and the performance appears questionable. Schwabe [10] suggested that the number of active sites for the O2 reduction on porous carbon electrodes is independent of Ab, as in the case of numerous catalytic reactions. 

Fig. 94. Schematic drawing of the configuration of Teflon-bonded platinum black electrodes close to the external surface...

The condition that the electrochemical processes occur largely in the region of the meniscus is only met if the thin film of electrolyte is absent or if the thickness is very small. The simple-pore model [64] is an example of the first case. The meniscus is assumed to form at the intersection of micropores with macropores. While the micropores are filled with electrolyte up to the intersection, the macropores are filled with gas. The meniscus may be treated as flat in a first approximation. The walls of micropores are the seat of the electrode reaction. The simple-pore model was suggested [64] as applying to non-wetted systems like the Teflon-bonded platinum black electrodes. The limiting current due to the diffusion of species into a micropore was derived [64] as the steady-state solution of the two-dimensional diffusion equation in cylindrical coordinates. The summation of the currents of the individual pores leads to ... 

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