Carbon electrode Tafel plot

In Figure 4 we have presented the experimental Tafel plots of air electrodes with catalysts from pure active carbon and from active carbon promoted with different amounts of silver. The obtained curves are straight lines with identical slopes. It must be underlined that the investigated electrodes possess identical gas layers and catalytic layers, which differ in the type of catalyst used only. Therefore, the differences in the observed Tafel plots can be attributed to differences in the activity of the catalysts used. The current density a at potential zero (versus Hg/HgO), obtained from the Tafel plots of the air electrodes is accepted as a measure of the activity of the air gas-diffusion electrodes the higher value of a corresponds to higher activity of the air electrode. 

Figure 7 Steady-state iR corrected Tafel plots of cathodic ORR performance of several binary Pt alloy electrocatalysts at 90 °C and 5-atm pressure. Performance for a Pt/C electrocatalyst is shown for comparison. The electrodes had 0.3mg/cm metal loading and the loading of the metal on carbon support was 20%. The humidifaction temperature for the anode and cathode gas streams were kept at 10 and 5°C above the cell temperature. 

The catalytic activity of the catalysts for the ORR is screened using a rotating-disk electrode (RDF) method. The activity of the new transition metal oxide catalysts is estimated by comparison to a standard RDE of 10 weight % platinumWulcan carbon, XC-72 (PtWC) catalyst (Alfa). The electrocatalytic activity of the catalysts are compared in Tafel plots of potential vs. current, calculated from the electrochemical data as described in the literature. 

Log Current Density (A/cm ) Figure 9-4. Tafel plot of carbon electrode... 

Figure 7.19 (A) Current-potential curves for the ORR on a glassy carbon electrode coated with Co-N/C. Recorded in a 0.5 M H2SO4 solution at various electrode rotation rates, as marked. Potential scan rate 5 mV s Co-N/C loading in the catalyst coating 0.10 mg cm" (B) Koutecky—Levich plots for the ORR on a Co-N/C-coated glassy carbon electrode, data from (A) and (C) Tafel plot, data from (A). Reprinted with permission from Ref. 65.

Figure 3 Plots of the total number of electrons Ut (a), of the Tafel slope b (b), of the limiting current density IjA,-, (c) and of the exchange current density I/A (d), versus the platinum loading for the reduction of oxygen on a platinum-modified polyaniline-glassy carbon rotating disk electrode (O2 saturated 0.5 M H2SO4 2mVs 25 °C A, is the true surface...

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