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Apparent exchange current density

Fig. 44. Cathode polarization. Apparent exchange current density of 3.3 x 10 5 A/cm2. Fig. 44. Cathode polarization. Apparent exchange current density of 3.3 x 10 5 A/cm2.
Consider the reaction with two consecutive electron-transfer steps described by Eq. (11.12). (a) Show that, if j0,2 j0,1, there is an intermediate range of negative overpotentials in which the apparent transfer coefficient is (2 — ai) and the apparent exchange current density 2j0,i (see Fig. 11.1). (b) Derive the form of the Tafel plot for jo,i > jo,2-... [Pg.152]

Using the charge-transfer resistances of the cathode and anode obtained by Wagner et al. [22], the apparent exchange current densities were calculated as Code = 0.1 Acm 2. and i athode = 6, uAcin 2 The results indicated that the cathode... [Pg.216]

Conway and co-workers [511, 512] studied the kinetics of chlorine evolution on the hydrous oxide film formed on Ir by potential multicycling. An increase of up to 180 in Cl2 evolution rate was observed (Fig. 22), the apparent exchange current density increasing almost linearly with oxide thickness. This enhancement in Cl2 evolution rate at the Ir-solution interface was mainly attributed to an increase in microscopic surface area with... [Pg.337]

Enhanced apparent exchange current densities noticed with increasing oxide thickness were attributed to an increase in real area of the electrode, coupled possibly with a change of the ratio of Ir(III)/Ir(IV) states in the oxide (JJS). There have been no attempts reported, with Ir-based electrodes, to relate behavior of adsorbed intermediates to the kinetic data by means of independent techniques. [Pg.107]

Work described in Ref. 86 includes a detailed investigation of the temperature dependence of ORR kinetic parameters at the Pt/bulk Nafion interface in the range from 30 to 90 °C. Plots of the log of mass-transport-corrected current density versus the potential of the Pt microelectrode showed an increase of a factor of about five in the rate of ORR at 0.90 V and about three at 0.85 V as the temperature was increased from 30 to 90 °C. The apparent activation energies for the two regions (low and high Tafel slope) were calculated from the dependence of the apparent exchange current density on T according to... [Pg.618]

Ratio of Apparent Exchange Current Densities versus Differences in Activation Voltage Losses (T = 340 K a = 0.5 n = 1)... [Pg.72]

For HOR Equation 2.24 should be used to estimate the ratio of apparent exchange current densities of two anodes. It is clear that the sought ratio is the ratio of the two slopes, and can also be expressed as... [Pg.72]

Platinum (Pt)-based catalysts are widely used as the anodic electrode material for hydrogen oxidation. The HOR on Pt catalysts has a lower oxidation overpotential and a higher kinetic rate. The apparent exchange current density of the HOR has been calculated to be =Q. Acm, which is extremely high... [Pg.33]

Since ao is known to be 2, the Iq can be calculated using Eqn (3.7) if R can be obtained through EIS measurement at OCV. Thus, the apparent exchange current densities for the ORR at different temperatures were obtained by this method and are listed in Table 3.1, where it can be seen that the value increased with increasing temperature. [Pg.106]

TABLE 3.1 Measured Apparent Exchange Current Densities of the ORR at 3.0 atm, 100% RH, and Different Temperatures [17]. MEA Nafion-112 -Membrane Based With an Active Area of 4.4 cm ... [Pg.106]

HOR. The apparent exchange current density of the HOR A cm calculated with Eqn (3.8) ... [Pg.107]

TABLE 4.1 Measured and Simulated Exchange Current Densities for the HOR and ORR in a Nafion -112-Membrane-Based PEM Fuel Cell at 3.0 atm (Absolute), 100% RH, and Different Temperatures, in a Low Current Density Range ( 02/H20 Measured Apparent Exchange Current Density for the ORR, 1° is the Simulated Apparent Exchange Current Density for the HOR, and fo2/H20 H2/h+ Intrinsic Exchange Current Densities for the ORR and HOR, Respectively)[8]... [Pg.136]

The relationship between the intrinsic exchange current density and the apparent exchange current density (ioj/Hio) described using the... [Pg.138]


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See also in sourсe #XX -- [ Pg.17 , Pg.34 ]

See also in sourсe #XX -- [ Pg.33 , Pg.57 , Pg.93 ]




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