Gas purging effect on the degradation characteristic of a proton exchange membrane fuel cell with dead-ended mode operation I. With different electrolytes

The effect of gas purging at the cathode on the degradation characteristics of dead-ended proton exchange membrane fuel cells (PEMFCs) is investigated herein using different electrolytes. Electrochemical techniques, including the measurement of polarization curves, cyclic voltammetry (CV) and surface and cross-sectional scanning electron microscopy (SEM) of tested the membrane electrode assemblies (MEAs), are applied to characterize the performance degradation of the fuel cells. The results show that mechanical failure of the membrane induced by the repeated gas purging in the fuel cell during dead-ended operation is the main cause of performance degradation. The performance degradation and the MEA failure mechanisms are not the same among the PEMFCs with different electrolytes. The Nafion® 211 (N211) undergoes much less degradation than Nafion® XL and Nafion® 115 (N115) after 1000 purge cycles under dead-ended operation of the fuel cell, as shown through the variation of the polarization curves, the electrochemical surface area (ECSA), and the membrane thickness. However, the mechanical properties of N211 were less favorable: after only 1000 purging cycles, the single cell with N211 experienced a dramatic voltage drop caused by pinholes on the membrane. In comparison, Nafion® XL and N115 can be subjected to 1600 cycles and 1800 cycles, respectively.