Abstract
Proton exchange membrane fuel cells (PEMFCs) with 0.1 and 0.4 mg Pt cm−2 cathode catalyst loadings were separately contaminated with seven organic species: Acetonitrile, acetylene, bromomethane, iso-propanol, methyl methacrylate, naphthalene, and propene. The lower catalyst loading led to larger cell voltage losses at the steady state. Three closely related electrical equivalent circuits were used to fit impedance spectra obtained before, during, and after contamination, which revealed that the cell voltage loss was due to higher kinetic and mass transfer resistances. A significant correlation was not found between the steady-state cell voltage loss and the sum of the kinetic and mass transfer resistance changes. Major increases in research program costs and efforts would be required to find a predictive correlation, which suggests a focus on contamination prevention and recovery measures rather than contamination mechanisms.
Highlights
Vehicles propelled by proton exchange membrane fuel cells (PEMFCs) are already commercially available
The cell voltage for the first 5 h is constant and higher for the 0.4 mg Pt cm−2 catalyst loading. This observation is consistent with previously published data for Gore catalyst coated membranes with the same cathode catalyst loadings and gas diffusion layers (Sigracet 25 BC) [24]
At irregular intervals and during all baseline, contamination, and recovery stages, cell voltage transients were minimally disrupted for a short period by impedance spectroscopy measurements and the superimposition of a current signal of a small amplitude and variable frequency
Summary
Vehicles propelled by proton exchange membrane fuel cells (PEMFCs) are already commercially available. A few publications discuss the impact of the anode catalyst loading during PEMFC exposures to reformate fuel contaminants, such as CO, CO2 , H2 S, NH3, and halogenated compounds. In comparison to the anode, the higher cathode potential is expected to affect the contamination mechanism with, for example, a different Pt surface charge, altered contaminant adsorbates and reaction intermediates, catalyst coverage, and cell voltage loss. This situation is exacerbated with a catalyst loading change, which affects the overpotential of the irreversible oxygen reduction reaction and the cathode potential. Impedance spectroscopy data were acquired to facilitate the development of predictive correlations and contamination mechanisms
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