Ohmic correction

Fig. 13. Stationary ruthenium dioxide/titanium dioxide electrode (UN5) in 5.13 M NaCl solution, (a) Standard rate constant-potential curve assuming a constant Tafel slope of 70 mV. DC) = 5 x 10 6cm s Z)C 2 = 7 x 10"6 cm s1, E = 1050 mV SCE, no ohmic correction, (b) Standard rate constant-potential curve assuming a constant Tafel slope of 70 mV. Z)C1 = 5 x 10"ecm s-1, Dc,2 = 7 x 10 6cm s, ° = 1050mV SCE, and R = 1.7 ohm cm2, (c) Standard rate constant-potential curve assuming a constant Tafel slope of 40 mV. DCI = 5 x 10-6cm s-1, Da = 7 x 10 9cm s->,fi° = 1050mV SCE, and ft = 1.7 ohm cm2, (d) Common experimental and calculated current-potential curve using the parameters of Fig. 13(c). The broken curve refers to the calculated "reversible curve.

At NEU, a series of electrocatalysts were synthesized based on classical colloidal sol synthesis techniques. These included platinum nickel/carbon (PtNi/C), platinum chromium/carbon (PtCr/C), and platinum cobalt/carbon (PtCo/C) together with the control Pt/C. All of the above electrocatalysts were prepared with 20% metal loading on carbon support (Vulcan XC-72, Cabot Corp). Ohmic corrected Tafel... 

Figure 4. Ohmic Corrected Tafel Plots for Oxygen Reduction on Pt and Pt Alloy Electrocatalysts Prepared at Northeastern (note that PtCr/C is a system being considered only for ORR fundamentals it will not be under consideration for down-selection)...

Figure 12.2 Current-voltage characteristic obtained in a 50-cm dihydrogen/air fuel cell at 353 K at a total pressure of 150kPa. The anode and cathode layers consist of about 50wt% Pt/C [0.4/0.4mgp(/cm (anode/cathode)] and ionomer (ca. 900 EW ionomer/carbon ratio = 0.8 1). Circles, experimental data triangles, mass-transport-free AEceii squares, mass-transport-free and ohmically corrected AEceii- The current density is referred to the geometric surface area of the MEA. (From ref. 4, with permission from Elsevier.)...

A) 50 single-cell H2—air performance at 7ceii = 80 °C. (B) Ecell versus / for the mass transport-free and ohmically corrected (i.e., /R-free) cel -i curve shown in A. (C) Addition of the ohmic losses, AEohmic, to the... 

FIGURE 3.14. Ohmic correction for hydrogen evolution, x — Raw data, = data corrected for ohmic drop. 

Hi) Frequency response methods. This method superimposes low-amph-tude, high-frequency (about 1000 Hz) AC signals over the DC potential supplied to the electrode. The response of the resulting AC component of current to changes in the frequency is analyzed to give information on a variety of electrode parameters including the ohmic correction. For details of the principle and its application, consult Refs. 24 and 25. 

Figure 4.23 Experimental Tafel plot of cell voltage versus current, corrected for fuel cell ohmic and other losses, so that only cathode polarization losses are remaining. The results are normalized to platinum loading. Results with open circles are with humidified oxygen, and closed circles are with humidified air. The dashed line represents the Tafel slope behavior. Note that for all loadings the Tafel slope for oxygen reduction on platinum is the same but deviates from this behavior under mass-limiting behavior. Also note that the vertical axis is ohmic corrected fuel cell voltage, not electrode overpotential, so the voltage falls with increasing current density. (Reproduced with permission from [9].)...

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