Experimental study on dynamic response characteristics and performance degradation mechanism of hydrogen-oxygen PEMFC during loading

Abstract

The instantaneous voltage overshoot caused by current loading is one of the important factors for the performance degradation of hydrogen-oxygen proton exchange membrane fuel cells (PEMFCs). In this study, the dynamic response characteristic parameters, including first-stage delay (FTD), second-stage delay (STD), and voltage undershoot (VU), were studied quantitatively to analyze the voltage changes during current loading. The effects of loading range and operating parameters including temperature, stoichiometric ratio, and relative humidity on dynamic response characteristics were experimentally analyzed. The results show that the FTD and the STD were shortened by a smaller loading amplitude. The FTD under the loading range of 200 mA/cm2-600 mA/cm2 was 0.5 s shorter than that under 200 mA/cm2-1000 mA/cm2, and the STD was shortened by 7.5 s. The STD was reduced by 30.9% with the operating temperature increased from 55 °C to 75 °C. What's more, the FTD and VU reached minimum values with the relative humidity of the anode and cathode controlled at 50% and 70%, respectively. In addition, it was found that after the current loading experiment, the performance decreased by 2.5%, the charge transduction resistance increased by 8.94%, and the electrochemical active surface area decreased by 11.68%. The findings reported are expected to provide guidance for optimizing the working conditions of hydrogen-oxygen PEMFC, to reduce the performance degradation caused by current loading and thus improve its working life.