Flow-field effect on reformate gas tolerance in post-doped HT-PEMFC

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are attractive for integration with methanol steam reforming, but reformate impurities strongly affect electrochemical kinetics and spatial current distribution. This study combines polarization analysis, electrochemical impedance spectroscopy (EIS) with distribution of relaxation times (DRT), and segmented current measurements to investigate degradation under CO 2 –CO reformate conditions. The results reveal clear flow-field-dependent mechanisms: serpentine channels show stronger low-frequency DRT contributions linked to cumulative gas-transport limitations, while parallel channels exhibit higher transport peaks but lower spatial poisoning severity. At elevated CO concentrations, voltage losses in the parallel configuration exceed those of the serpentine by ∼15%, with a ∼1.7 × increase in the fast DRT process contribution. Spatial analysis shows channel-governed degradation gradients in serpentine flow fields, whereas parallel channels exhibit preferential poisoning of initially strongest segments. Water vapor partially mitigates poisoning, improving spatial recovery to ∼0.27 A/segment.