Manufacturing defects in slot die coated polymer electrolyte membrane for fuel cell application

Abstract

Degradation of polymer electrolyte membrane (PEM) is among the major hurdles for the commercialization of the PEM fuel cells. All of the previous studies on degradation of membrane assumed they were pristine and void of defects that would contribute to the degradation of the cell, although, preexisting defects may seriously contribute to membrane degradation. In this research, manufacturing defects in PEM have been reported. A slot-die coating method using in house roll-to-roll manufacturing system has been used for the membrane manufacturing. Various micron sized defects such as cavities, cracks, non-uniform thickness, contamination, and air-bubble have been observed in the membrane. These defects may create spatial variation in the membrane properties, membrane electrode assembly imperfections and localized weak zones and can serve as initial points for membrane degradation. Further, pristine and defected membranes have been used in the fuel cell and the cell performance have been compared. The defected membrane was found to have a lower open circuit voltage due to higher hydrogen crossover. However, the polarization curve of the fuel cell with the defected membrane was found to be similar to the one with a pristine membrane. Overall, the present research evidence that defects can be present in membrane, however they may not alter the fuel cell performance initially. To understand the long term effect of the defects on fuel cell performance further studies are needed. A linkage between membrane defects and fuel cell performance is crucial in identifying the threshold of the manufacturing defects that are acceptable in the fuel cell assembly and the present study serves as the first step in this regard.