Dynamic current cycles effect on the degradation characteristic of a H2/O2 proton exchange membrane fuel cell

Abstract

The durability and reliability of H2/O2 proton exchange membrane fuel cell (PEMFC) is a key factor that prevents its wide application in the civil field. PEMFC inevitably experience different dynamic loading cycles according to different power switching requirements during practical operation. To explore the degradation behavior under different dynamic cycles, a single H2/O2 PEMFC with 50 cm2 active area was operated under the circulating current density from 100 mAcm−2 to 600 mAcm−2, 100 mAcm−2 to 800 mAcm−2, and 100 mAcm−2 to 1000 mAcm−2, respectively. The change of polarization curve, performance degradation at different current density, Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) were characterized to investigate the performance degradation over dynamic current cycles. Besides, the Scanning Electron Microscopy (SEM) was used to evaluate the degradation of catalyst layer. The results indicated that the degradation rate of the fuel cell performance increased corresponding to the cycle number, at 1200 mA/cm2, it with a total performance degradation rate of 11.83% after 2000 dynamic loading cycles with the circulating current density from 100 mAcm−2 to 600 mAcm−2. The degradation of electrochemical performance such as CV and EIS was consistent with that of fuel cell performance. The degradation rate is accelerated with the increase of loading cycle number and load step amplitude. What’ more, EIS provides additional sensitivity to differentiate catalyst layer degradation within PEMFC. Moreover, the degradation of the catalyst layer became much more severe under a larger load step amplitude.