Bipolar Plates for PEMFC

Individual PEMFC cells produce about 0.7 V electromotive force (EMF). In order to obtain useful voltage, many cells are stacked together using a bipolar plate. It should be noted that the membrane electron assembly (MEA) for PEM is kept very thin, but the bipolar plates constitote almost 80% of the mass of PEMFC. The bipolar plate acts as an interconnect between the anode of one cell and the cathode of the next. Bipolar plates also distribute the fuel gas over the anode and oxygen over the cathode. These bipolar plates also contain cooling fluid and the different flow field patterns of bipolar plates used in PEMFC are shown in Fig. 1.12. Bipolar plates should have the following characteristics  

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T. D. Burchell, Carbon Composite Bipolar Plates for PEMFC, 26 Annual International Conference on Advanced Ceramics and Composites, January 13-18, Cocoa Beach, FL. 

General reviews and design analyses concerning bipolar plates for PEMFCs have been carried out periodically [10-14], and the bipolar plate materials are commonly divided into composite and metallic materials. Efforts with composite materials have been carried out in research organizations and industry worldwide [15-23]. Wilson and co-workers developed a composite bipolar plate with a vinyl... 

Table 6.1 shows a lack of homogeneity in the definition of bipolar plate requirements. Nevertheless, there has been a differentiation between graphitic and metallic bipolar plates for PEMFC since 2006, as the ways of fabrication and feasible geometries are widely different and stationary, portable and automotive applications are distinct. 

Carbon/carbon composite bipolar plates for PEMFC (DOE, 2006). 

Proyair Fuel CEll Technology Deyelopment carbon/carbon composite bipolar plates for PEMFCs. To develop high-volume production of composites bipolar plates... 

Bipolar plates in PEMFCs were conventionally made of graphite with excellent corrosion resistance, chemical stability, and high thermal conductivity. However, graphite has a high cost, poor mechanical properties, and very little formability due to its microstructural nature. This limits its further applications as plate material and forces a search for alternative solutions. Nevertheless, the performance, durabilify, and cosf of fhe graphite plate (e.g., POCO graphite and graphite plates) have been taken as benchmark references to compare with those of alternative materials. 

From energy-density and volume-production points of view, the use of metallic bipolar plates in PEMFC stacks is important for the automobile industry. Metallic bipolar plates could provide thinner and hghter choices and improved thermal and bulk electrical conductivity. The use of SSs makes PEMFCs cost-effective. Whereas 316/316L SS may not be the optimum choice for the PEMFC bipolar plate... 

Graphite/polymer composite PEMFC bipolar plates for higher temperatures (120 C) and automotive applications (DOE, 2009). 

Metal PEMFC bipolar plates for transportation applications (Antunes, 2010). 

Joseph, S., J.C. McClure, R. ChianeUi et al. 2005. Conducting polymer-coated stainless steel bipolar plates for proton exchange membrane fuel cells (PEMFC). International Journal of Hydrogen Energy 30 1339-1344. 

The costs of a PEMFC stack are composed of the costs of the membrane, electrode, bipolar plates, platinum catalysts, peripheral materials and the costs of assembly. For the fuel-cell vehicle, the costs of the electric drive (converter, electric motor, inverter, hydrogen and air pressurisation, control electronics, cooling systems, etc.) and the hydrogen storage system have to be added. Current costs of PEM fuel-cell stacks are around 2000/kW, largely dominated by the costs of the bipolar plates and... 

In PEMFCs working at low temperatures (20-90 °C), several problems need to be solved before the technological development of fuel cell stacks for different applications. This concerns the properties of the components of the elementary cell, that is, the proton exchange membrane, the electrode (anode and cathode) catalysts, the membrane-electrode assemblies and the bipolar plates [19, 20]. This also concerns the overall system vdth its control and management equipment (circulation of reactants and water, heat exhaust, membrane humidification, etc.). 

The design of BP for PEMFCs is dependent on the cell architecture, on the fuel to be used, and on the method of stack cooling (e.g., water or air-cooling). To date, most of the fuel cells have employed traditional filter-press architecture, so that the cells are planar and reactant flow distribution to the cells is provided by the bipolar plate. The bipolar plate therefore incorporates reactant channels machined or etched into the surface. These supply the fuel and oxidant and also provide... 

Grigoriev S.A., Alanakyan Yu.R., Fateev V.N., Rusanov V.D., Blach R. Bipolar plates and current collectors for PEMFC. Modeling of the mass transfer processes. Book of abstracts of the 2002 Fuel Cell Seminar (18-21 November 2002, Palm Springs, USA), p.21-24. 

Polymeric functional materials are of central importance for the polymer electrolyte membrane fuel cell (PEMFC) and DMFC technologies in particular. In addition to the expected cost reduction due to low-cost mass productimi, for example of polymeric bipolar plates (see Sect. 2.1), the polymeric membranes are irreplaceable in the PFMFC and DMFC technologies. 

Beside the MEA the bipolar plates are the key components in a PEMFC stack in terms of their contribution to weight, volume, and costs. Bipolar plates contain a fine mesh of gas channels called the flow-field, to ensure a uniform distribution of the process gasses (hydrogen and oxygen) of fuel and air across both sides of the MEA and the removal of the reaction products. Furthermore, the bipolar plates in PEM fuel cells separate the individual cells from each other and guarantee an electrical connection between them in series. Substantial requirements for the bipolar plates are a high electrical conductivity and corrosion resistance. 

As matrix polymers for the bipolar plate standard thermoplastic and technical polymers can be considered. For the developments at the Fraunhofer ICT polypropylene (PP) was used as a suitable polymer because of its material properties and also its low material price. With a service temperature of 100 °C PP is in the uncritical temperature range for the operating conditions in a PEMFC. 

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