Characterization studies on PEM metallic bipolar plates and membrane electrode assembly

Metallic bipolar plates seem more appropriate than graphite composite bipolar plate, that is currently considered the industry standard for PEM fuel cell operation. Metallic plates have higher mechanical strength, easier manufacturability, and lower interface contact resistance than graphite composite plates. Metallic and graphite composite plates were tested one thousand hours under normal operating conditions and cyclic loading. After operation, bipolar plates, membrane electrode assembly and byproduct "water" samples were collected and tested from both the cathode and anode side of a single cell. Characterization studies were then conducted on aluminum coated bipolar plates with carbide based alloy to examine for any possible chemical changes in the composition of the coating and/or the membrane electrode assembly (MEA) that may affect the stability of the coating, substrate, and/or the ionic conductivity of the cell. Scanning electron microscope (SEM), and energy dispersive X-ray (EDX) analysis were performed on the land and valley surfaces of the reactant flow fields at both the anode and the cathode. The measurements were super imposed to identify the locations and zones of anomalies to conduct further analysis focused on these zones. X-ray diffraction (XRD) analysis were also conducted on samples scraped from the anode and cathode electrodes of the MEA that was also performed for 1000 hrs in metallic bipolar plate fuel cell. Moreover, samples of water as a byproduct produced during the single fuel cells operation were also collected and tested for the existence of chromium, nickel, carbon, iron, sulfur and aluminum using mass spectroscopy analysis technique. The analysis of the EDX measurements indicated the possibility of the dissociation and the dissolution of the nickel chrome that is used as the binder for the carbide based corrosion resistant coating with the substrate. The X-ray analysis yielded the tendency for catalyst growth that could result in powe- - r degradation.