Long‐term Operation of High Temperature Polymer Electrolyte Membrane Fuel Cells with Fuel Composition Switching and Oxygen Enrichment

Abstract

The performance of commercially available High temperature polymer electrolyte membrane fuel cells (HT‐PEMFCs) cells was electrochemically (impedance spectroscopy, polarization curves, performance over time) and optically characterized ante and post mortem via micro‐computed tomography. Investigations on the performance gain, due to oxygen enrichment of cathode air and the capabilities of the commercial MEAs to switch and operate between pure hydrogen and synthetic dry reformate (78% H2 and 22% CO2), were carried out. Two experiments at constant load conditions were performed, Cycle 1 consisted of 12 h pure hydrogen operation followed by 12 h of synthetic reformate, while Cycle 2 was operated with 1 h of H2 followed by 5 h of synthetic reformate. The results revealed that oxygen enrichment improves mass transport from the gas flow channels to the cathode catalyst layer as well as catalyst utilization. Thus, oxygen concentration increase from 21% (air) to 30% at 0.3 A cm−2 developed a performance improvement of roughly 8%. Only marginally influence on fuel cell performance and degradation was observed in fuel switching experiments. A content of 22% CO2 had little influence on degradation, which could mainly be related to fuel dilution. Besides, micro‐computed tomography (µ‐CT) investigations revealed similar membrane and catalyst layer degradation for both kinds of fuel switching tests.