| Popis: |
Distribution of relaxation times (DRT) is calculated from fifty local impedance spectra of a low–Pt PEM fuel cell. 48 out of 50 DRT spectra contain three peaks. Evolution of the peak frequency positions and resistivities with the cell current density are analyzed. The analysis allows us to attribute the low–frequency peak to oxygen transport in the gas–diffusion layer (perhaps, including transport in the channel), the middle peak to unresolved processes of charge–transfer and oxygen transport in the ionomer film, and the high-frequency peak to oxygen transport in void pores of the catalyst layer. Comparison of DRT spectra of low–Pt and high–Pt cells suggests a method for measuring ionomer film transport resistivity in a low–Pt cell. |
