Additive Manufacturing of Bipolar Plates for Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) are an excellent renewable energy alternative to the modern-day transportation applications. A crucial component of these fuel cells are bipolar plates (BPPs). Although these plates are one of the most important parts of the fuel cell, they also make up 80% of the fuel cell’s weight, 50% of its volume, and 40% of its cost. To improve these disadvantages and innovate BPP technology, facilitating effective fuel cell commercialization, it is highly important to advance current plate prototyping and fabrication methods. In this thesis, the use of additive manufacturing for BPPs in PEMFCs is investigated to determine its feasibility as a solution to specifically improve metallic BPP prototyping. BPPs were fabricated using 17-4 precipitation hardening (PH) stainless steel with three different manufacturing methods: direct metal laser sintering (DMLS) at the University of Connecticut (UConn), selective laser melting (SLM) at American Additive LLC., and machining at UConn. Characterization techniques such as scanning electron microscopy (SEM), optical microscopy (OM), x-ray diffraction (XRD), tensile testing, contact angle analysis, and interfacial contact resistance (ICR) measurements were used to characterize and compare the samples. The plates were coated by gold sputtering to prevent surface oxidation during testing. Polarization curves and electrochemical impedance spectroscopy (EIS) were performed for each of the manufactured BPPs (uncoated and gold coated) using commercial membrane electrode assemblies (MEAs) in a single cell. The performance of all manufactured plates was compared between each other and with a commercial graphite BPP. Fuel cell runs showed that gold coated machined and American Additive plates were very comparable to each other although their performance was still lower than that of graphite plates. Uncoated American Additive plates performed better than uncoated machined plates, but poorer than the graphite plates. UConn AM plates did not pass the leak test, so a vacuum resin impregnation technique was used to seal the plate and the plate was used on the cathode side along with a graphite plate on the anode side. Uncoated UConn AM and graphite plate assembly showed promising results, but after gold coating, performance of the cell became worse with each run. Uneven coating and leftover surface features from hand polishing could have been attributed to this. The obtained results show that AM presents a promising solution for prototyping of metallic BPPs. However, special care in terms of material selection, build parameter optimization, and coating technique needs to be given to make AM available for commercial or industry use.