Oxidation current density

Current density per imit uncovered area was calculated by dividing the methanol oxidation current density by 1-6 methanol as ... 

Fig. 3-19 Modified methanol oxidation current density. Current density was divided hy (1— OSHSA) in 5 M H2SO4 with 0.1 M CH30H. 

Fig. 3-24 Iiifethanol oxidation current density of platinum after 2 min, of potential holding at 600 mV in various concentration of H2SO4 with 0.1 M CH3OH. ESach curve is extrapolated to the boiling point of the respective solution (black points). 

Oxide Current density Oxide Current density... 

For reformate with a high CO concentration (>10 ppm), a PEM fuel cell with a Pt/Ru alloy anode still suffers from a substantial cell voltage loss, especially in the high-CD region, because the maximum CO oxidation current occurs from 0.39 to 0.6 At its onset potential (<0.1 V), the CO oxidation current density of a Pt/Ru anode is capable of oxidizing only a few ppm CO. The ignition potential, defined as the potential at which the CD increases by approximately two orders of magnitude... 

In conclusion, the presence of both poisoning species (mainly CO) and intermediate reaction products (AAL, AA) decreases correspondingly the useful energy density of the fuel, and also the power density, since the oxidation current densities are lower than those obtained with the oxidation of methanol and above all of hydrogen. To improve the kinetics of ethanol oxidation would require the development of new electrocatalysts able to break the C-... 

Figure 15 Potentiodynamic (ImV/s) oxidation current densities for 0.1% CO/H2 on sputter-cleaned Pt and Pt-Ru RDEs at 2500 rpm in 0.5-M sulfuric acid at 62 °C. Prior to electrochemical measurements, the electrode potential was held at 0.05 V at 2500 rpm for about 300 s. (a) Magnification of the low-current density region for the positive going sweeps, (b) Comparison of the potentiodynamic and potentiostatic (1000-s) oxidation current densities, (c) Potentiodynamic (20mV/s) oxidation of pure H2 on CO-poisoned Pt (Pt-CO/ H2) CO was adsorbed at 0.05 V, and then the electrode was cycled between 0.05 and 0.22 V in CO-free solution (Pt-CO/no H2) the voltammetry of the unpoisoned Pt surface at the same conditions is added for reference.

Figure 17 Potentiodynamic (0.1 V/s) oxidation current densities for several H2/CO mixtures on a PtRu-colloid/Vulcan electrode (7 pg/cm ) at 60°C and 2500 rpm. The upper abscissa gives the kinetic current density while the lower uses a scale-up factor of 143 to simulate the performance of a fuel-cell electrode. The electrooxidation of pure H2 at the same electrode is shown for reference. (From Ref. 58.)...

In the current version of the MPM, which was developed for modeling the ECP of Type 304 SS in BWR primary circuits, the steel oxidation current density, icorr.was modeled as an empirical function of voltage, based on the data of Lee (see Ref. 36),... 

Fig. 3.4 Diagram illustrating dynamic equilibrium for the metal reaction M = Mm+ + me, where the oxidation current density, iox M, is equal to the reduction current density, ired M.

In the derivations of Eq 3.14 and 3.19 for the metal oxidation current density, iox M, and the metal-ion reduction current density, ired M, it was not necessary to restrict the half-cell potential to its equilibrium value. Deviation from E M will occur if the potential of either the metal or the solution is changed, resulting in an overpotential defined in general by Eq 3.1. More specifically, small deviations are associated with charge-transfer polarization, and the overpotential is designated as ... 

With an oxidation overpotential, the removal of electrons from the electrode makes it more positive relative to the solution, an effect that the electrode attempts to counteract by increasing the rate of transfer of ions from metal to solution (i.e., ioxM is increased and iredM is decreased relative to their equilibrium value, i0 M), giving a net oxidation current density. 

Figure 19. Methanol oxidation current density on Pt (—) and Pt/Ru after 1st...

Figure 24. Graph showing the correlation between methanol oxidation current density (after reaching the steady-state) and 2it " rf DOS. (Reprinted with permission from Copyright 2002 Am. Chem. Soc.)...

The oxidation current density versus the scan rate is approximately linear in the range of 20—100 mV/ s. The exponent of scan rate, x, value was found to be 0.6, indicating that the kinetics of the redox process is almost controlled by the diffusion process.This means that insertion/desertion of CIO4 ions is responsible for the charge electroneutrality during the redox process of PBCHDPM. 

Fig. 2.5 (a) Potentiostatic methanol oxidation current densities at 500 mV in 0.5 M methanol and (b) Potentiodynamic (20 mV/s) CO oxidation current at rotation rate of 1,600 rpm. Others 0.5 M H2SO4 (Reprinted from [49], Copyright (2011), with permission from Elsevier)... 

Figure 51. Discharge characteristics of some lithium-nickel oxides (current density 0.25 mA cm" ).

FIG. 10—Plot of permeation rise transient H oxidation current density expressed as the ratio of the transient current density to the steady state current density (Y = /(l)//(°o) versus x = (DlU)t The constants associated from the breakthrough and lag time methods can be obtained from this plot. Selected values are given in Table 3. 

Indeed, the presence of both poisoning species density, since the oxidation current densities are (mainly CO) and intermediate reaction products lower than those obtained with the oxidation of... 

After 10 h of operation the presenee of Ru islands on Pt inereased the oxidation current density approximately 20-fold in the case of PtRu-53, followed closely by PtRu-35. Combining cyclic voltammetry with surface NMR two COad populations were identified COad close to (or possibly on) Ru sites undergoing fast thermally activated diffusion and COad on Pt characterized by slow diffusion [91]. These two types of COad are responsible for two separate peaks in CO stripping voltammetry, at low ( 0.3 V) and high (above 0.4 V) potentials, respectively. Ru decreases the activation barrier for COad surface diffusion by reducing electron back-donation. 

Figure 4.15. Comparison between Pt decorated with Ru ( ) and a commercial Johnson Matthey PtRu alloy catalyst (o). Methanol oxidation current density measured after 20 h in 0.5 M CH3OH - 0.5 M H2SO4 293 K. Potential referred vs. SHE. [98]. (Reprinted from Journal of Catalysis, 203, Waszczuk P, Solla-Gullon J, Kim H-S, Tong YY, Montiel V, Aldaz A, et al.. Methanol electrooxidation on platinum/mthenium nanoparticle catalysts, 1-6, Cop3Tight2001, with permission from Elsevier.)...

Iwasita et al. found that the alloy (PtRu atomic ratio of 5.66 1) gave more flian four times higher oxidation current density at 0.5 V vs. RHE in 0.5 M CH3OH -0.1 M HCIO4 compared to the Pt(lll)/Ruad formed by spontaneous adsorption (Figure 4.17) [104]. 

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