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Hydrogen is considered as an environmentally friendly storage medium for renewable energies and has attracted extensive attention, since it can provide 2.5 times as much energy per unit mass as fossil fuels, and provide hazard-free products. As an effective method for hydrogen production, the proton exchange membrane electrolyzer cell (PEMEC) provides a number of advantages: rapid response to the power input, compact system design, high purity product (up to 99.995%), high operation current density (above 2 A/cm2), and high operation pressure (up to 350 bar). Due to insufficient performance and high cost of PEMEC stacks, the use of hydrogen as large-scale energy storage with PEMECs has been limited so far. Thus, low-cost and high-efficiency PEMECs are highly desirable to establish a clean and sustainable energy infrastructure. To bridge the gap between lab-scale and industrial hydrogen productions, the main objectives in this research include: (1) Exploring the possibility of application of metallic additive manufacturing (AM) on PEMECs. (2) Integrating the components of PEMECs into one part with better performance and compact system design by using AM technologies. (3) Bipolar plate development with AM and protective coating for durable and high-efficiency PEMECs. (4) Combination of AM non-conductive bipolar plate with thin film liquid/gas diffusion layers for low-cost hydrogen production. (5) Developing conductive mesoporous bi-material catalysts with ultra-high reaction sites and efficiency for oxygen evolution reaction in PEMEC by using advanced manufacturing. Those bipolar plates and membrane electrode assemblies (MEAs) with excellent electrochemical performance and low cost will open a pathway for developing widely available water electrolyzers or other energy conversion devices, such as batteries, solar cells, and fuel cells.

Fuel cells are electrochemical energy conversion devices that convert chemical energy to electrical energy efficiently. Bipolar plates form an integral part of a fuel cell and their high manufacturing cost and low production rate have hindered the commercialization of fuel cells. Bipolar plates require high electrical conductivity, strength, chemical resistance and thermal conductivity. This thesis presents efforts to manufacture bipolar plates which meet these requirements using compression or injection molding. Compression or injection molding processes allow cost-effective, large-scale manufacturing of bipolar plates. A variety of material systems for the fabrication of bipolar plates are processed, molded and characterized.

Bipolar plates compose a large portion of the weight and manufacturing costs in fuel cells. Bipolar plates are metal plates that separate each membrane-electrode assembly in a fuel cell stack. They provide structural strength, contain flow channels for fuel transport, and conduct electricity in the fuel cell. Electricity also flows through the gas diffusion layer (GDL) which lies next to the bipolar plate. Because the GDL is separate from the bipolar plate, there is a contact resistance as the electricity flows from one to the other. The scope of this thesis is to research an efficient way of manufacturing a cheap and lightweight bipolar plate-GDL combination. This is to be done by using materials such as exfoliated graphite, a binding resin, and sacrificial additives. Processing temperatures and pressures as well as component ratios are variables to be investigated in order to easily and quickly make bipolar plate-GDL combinations.

The development, design, and modeling of a rapid continuous processing scheme is developed to economically manufacture conductive polymer composite bipolar plates for fuel cells. Bipolar plates are required to possess several important properties for fuel cell operation, with the most sought after being electrical conductivity and mechanical strength. The polymer composite material generated at Virginia Tech is based on material generated by a wet-lay process and uses polyethylene terepthalate (PET) or polyphenylene sulfide (PPS) as the binder, although PPS is mainly used. In order to reach sufficient conductivity for use in generating bipolar plates, the polymer is doped with high levels of conductive graphite particles in the range of 70-80 wt%. The polymer system is reinforced with 6-9 wt% glass or carbon fibers. When compression molded into a solid, flat preform, the wet-lay material exhibits excellent bulk (in-plane) conductivity (> 250 S/cm). The material also exhibits tensile and flexural strengths of 57.5 and 95.8 MPa, respectively, higher than other polymer composite material being considered for bipolar plate production. However, formability and through-plane conductivity needs improvement. The laminate bipolar plates developed at Virginia Tech are made using wet-lay material in the core and a thermoplastic/graphite mixture on the surfaces. The wet-lay material provides mechanical integrity, while a powder form of PVDF or PPS and graphite mixture added to the surfaces to improve through-plane conductivity and formability. The manufacturing scheme for the production of laminate bipolar plates is based on the pre-consolidation of the wet-lay material, which establishes a solid, flat surface for the continuous addition of laminate powder. Because the laminate powder only requires heating, radiation heating is used in the process design to pre-heat the preform prior to compression molding. The heated preform passes underneath a press, where forming of channels takes place along with cooling of the bipolar plate. It is estimated that the entire process can take one minute to produce a bipolar plate. The cost of manufacturing a bipolar plate is estimated to be $8/kW, below the goal of $10/kW. The annual production is determined to be 250,000, with over 500,000 possible depending on certain design factors.