Study on relationship between low-frequency impedance and internal states of polymer electrolyte membrane fuel cell based on mass transfer and impedance model

Abstract

Using fixed-frequency impedance based on electrochemical impedance spectroscopy (EIS) for fault diagnosis is an important trend of polymer electrolyte membrane fuel cell (PEMFC). However, the quantitative relationship between the low-frequency impedance and the internal states of the PEMFC (water content, oxygen concentration, etc.) is worthy but insufficiently studied yet. To fill this gap, a model combining PEMFC mass transfer and impedance is established, calibrated and verified. Based on this, the relationship between internal states of PEMFC and the amplitude and phase of the low-frequency impedance is analyzed. The results reveal that internal states affect the low-frequency impedance by affecting four types of resistances (charge transfer resistance Rc, membrane resistance Rm, proton transfer resistance Rp and oxygen diffusion resistance Rd). Rc, Rm and Rp are the dominant factors of the low-frequency impedance at low humidity and low current density while Rc and Rd are the dominant factors at high humidity and high current density. Additionally, all resistances positively impact the amplitude of the low-frequency impedance with a successively decreasing influence magnitude of Rm, Rc, Rd, Rp. The phase is positively correlated with Rc and Rd while negatively correlated with Rm and Rp.