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Platinum Tafel process

The anodic evolution of oxygen takes place at platinum and other noble metal electrodes at high overpotentials. The polarization curve obeys the Tafel equation in the potential range from 1.2 to 2.0 V with a b value between 0.10 and 0.13. Under these conditions, the rate-controlling process is probably the oxidation of hydroxide ions or water molecules on the surface of the electrode covered with surface oxide ... [Pg.372]

FIGURE 1.7 Tafel lines for a simple organic oxidation process comparing platinum with a better electrocatalyst A. [Pg.11]

Other surfaces, typically platinum, show pH-dependent processes which have been variously explained. Damjanovic and Brusic believe that the rds is similar to reaction (93) under Temkin conditions, with a Tafel slope or RT/F ... [Pg.231]

Zurilla et al. have reported kinetic data for O2 reduction and peroxide oxidation on gold in akaline solutions which indicate that the Tafel slopes for the O2 reduction to peroxide as well as the reverse oxidation process are both numerically -0.12 V/decade at 25°C in ultrapure solutions without any platinum contamination.t As with the pyrolytic graphite the stoichiometric number is 2.0 with the reduction reaction first order in O2 and zero order in OH in alkaline solutions over the pH range examined (11.5-12.7). This implies a mechanism similar to that on pyrolytic graphite in alkaline solutions, based on the data of Morcos and Yeager. [Pg.364]

Analytical solutions have been developed for the polarization of porous electrodes limited by either mass-lranspOTt ot ohmic losses through the depth of the electrode (Perry et al. 1998). When either of these processes is important, a porous electrode displays a double Tafel slope. It can be shown from (32)-(34) in Perry et al. (1998) that electrodes limited by either kinetic, transport, or ohmic losses have the same dependence on surface area loss. This argument holds only if the platinum particles remain nniformly distributed through the depth of the electrode. [Pg.370]

Equation (8.52) is of the form of the Tafel equation (8.33) which suggests that b is approximately 0-03. Such a value is rarely encountered in practice although it is observed in the case of platinized platinum. The above treatment does not allow for the fact that the pH of the solution will be modified by the adsorption process, relative concentrations of free and adsorbed atoms being given by the Freundlich isotherm... [Pg.197]


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See also in sourсe #XX -- [ Pg.322 ]




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