Performance Study of a Fuel Cell Pt‐on‐C Anode in Presence of CO and CO 2, and Calculation of Adsorption Parameters for CO Poisoning

Abstract

A study was undertaken to measure polarization losses due to the presence of and in the fuel for a practical fuel cell Pt/C anode. A porous Pt anode (0.3 mg/cm2 Pt) was tested as a floating electrode in a half‐cell assembly to measure performance in 100 weight percent at 190°C in presence of , and , , and gas mixtures. The additional polarization loss over that of due to dilution followed closely the expected loss from the Nernst equation in the range of current density 0–300 mA/cm2. The combined loss due to poisoning by and the dilution by and was analyzed and found to be additive of the poisoning and dilution losses. The poisoning loss by was calculated by subtracting the dilution loss from the combined dilution and poisoning loss. Such data were found to be linearly dependent on the logarithm of ratio. This is consistent with poisoning by replacement of sites on the porous Pt electrode. The calculated values of surface coverage by ranged from 0.089 to 0.31 as the ratio varied from 0.01 to 0.025. The values of surface coverage were consistent with the dual site elimination model for the replacement of by molecules. The exchange current densities for oxidation varied from 309 to 142 mA/cm2 as the ratio changed from 0 to 0.025. By comparing the experimental isotherm for adsorption with the Temkin isotherm, the interaction parameter was calculated to be 3.83 kcal/mol, and the standard free energy of adsorption, −10.96 kcal/mol. The latter value indicated an adsorption of which is comparable to .