Experimental investigation of PEM fuel cell aging under current cycling using segmented fuel cell

Abstract

The effect of inhomogeneous humidification on the local aging of the membrane electrode assemblies (MEAs) was investigated using segmented fuel cells under current cycling conditions. The active area of the MEA was divided into 8 segments along the flow channels. The effects of the local humidification of the MEA were measured by the high frequency resistance (HFR). It was found that the HFR of the first segment was largest due to the lower humidification. The concentration of water and water vapor was higher downstream, the MEA was humidified, and consequently the value of HFR also decreased. The fuel cells were operated at 60% RH, cell temperature 60 °C for uniform cell performance, with current cycling between 700 and 70 mA/cm 2. The polarization curve showed less differentiation between each segment after 450 cycles and 150 hours of the current loading test. The MEA was exposed to cycling expansion and contraction during the drying and humidification processes, respectively. The results suggest that the membrane might experience mechanical degradation in downstream segments. In addition, the slope of the cyclic voltammetry (CV) curves increased from region 6 to region 8. The surface area of the catalyst also decreased due to the downstream water flooding, which might block the mass transfer and result in fuel starvation, carbon corrosion and catalyst degradation.