Degradation study of high temperature proton exchange membrane fuel cell under start/stop and load cycling conditions

Abstract

The unreliable durability of high temperature proton exchange membrane fuel cells (HT-PEMFCs) is one of the restriction factors upon the commercialization process. In this paper, 600-h accelerated stress tests (ASTs) were performed on HT-PEMFCs to investigate the performance degradation under start/stop, load cycling (0.2–0.8 A cm−2 and 0.04–0.2 A cm−2) conditions. The activation, ohmic and mass transport polarization losses were determined in combination with the electrochemical impedance spectroscopy (EIS) and Tafel slope analysis, and the degradation modes such as carbon corrosion, catalyst degradation, acid loss and membrane degradation were analyzed by linear sweep voltammetry (LSV), cyclic voltammetry (CV) and transmission electron microscopy (TEM) characterization. The polarization curves of ASTs show that load cycling between 0.04 and 0.2 A cm−2 extensively aggravates performance degradation, indicating that high-potential operation has the greatest detrimental impact on the durability. By comparing the changes of the activation, ohmic and mass transport polarization losses, it can be found that the activation polarization is the dominant factor leading to performance degradation in the 600-h test, and the ohmic polarization has little effect on the performance degradation. After the test at load cycling between 0.2 and 0.8 A cm−2, the membrane is seriously degraded and the ohmic resistance increases significantly, and the severe acid loss becomes critical issue in the long-term durability of HT-PEMFC.