Analysis of degradation mechanism in unitized regenerative fuel cell under the cyclic operation

Abstract

The degradation of Unitized Regenerative Fuel Cell (URFC) performance is a key issue hindering its further development. In this study, an experimental measurement protocol for URFC degradation was established and two durability tests were carried out through the cyclic experiment and comparative experiment. The round-trip efficiencies (RTE) of the cell decay from 45% to 31.9% and is accompanied by a significant increase in ohmic and mass transfer impedance of over 91.2%. The experimental results confirm that the degradation occurs mainly in the water electrolysis (WE) mode, and accelerates with increasing electrolytic voltage. By characterizing cell components after degradation, carbon corrosion on the MPL side of the GDL is found to be the main cause of the degradation of the URFC, with over 31% of the area corroded based on image processing methods. Further analysis of the effects of carbon corrosion reveals that the corrosion of the GDL does not directly cause an increase in electronic resistance but rather destroys the microporous structure between the CCM and the GDL which in turn leads to a reduction in the water transport capacity of the interface. This not only causes an increase in the resistance to water transport but more importantly, causes a decrease in hydration of the proton exchange membrane (PEM), leading to a sharp increase in the CCM proton conduction resistance. Our perspectives are confirmed by subsequent verification experiments of GDL replacement. Ultimately, an intrinsic mechanism between the URFC performance degradation and carbon corrosion is established.