Bipolar plates PEMFC

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... 

Figure 4.1 shows a schematic of a typical polymer electrolyte membrane fuel cell (PEMFC). A typical membrane electrode assembly (MEA) consists of a proton exchange membrane that is in contact with a cathode catalyst layer (CL) on one side and an anode CL on the other side they are sandwiched together between two diffusion layers (DLs). These layers are usually treated (coated) with a hydrophobic agent such as polytetrafluoroethylene (PTFE) in order to improve the water removal within the DL and the fuel cell. It is also common to have a catalyst-backing layer or microporous layer (MPL) between the CL and DL. Usually, bipolar plates with flow field (FF) channels are located on each side of the MFA in order to transport reactants to the... 

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. 

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.). 

In this chapter, after recalling the working principles and the different kinds of fuel cells, the discussion will be focused on low-temperature fuel cells (AFC, PEMFC, and DAFC), in which several kinds of carbon materials are used (catalyst support, gas-diffusion layer [GDL], bipolar plates [BP], etc.). Then some possible applications in different areas will be presented. Finally the materials used in fuel cells, particularly carbon materials, will be discussed according to the aimed applications. To read more details on the use of carbon in fuel cell technology, see the review paper on The role of carbon in fuel cell technology recently published by Dicks [6],... 

An elementary PEMFC comprises several elements and components the membrane-electrode assembly (MEA), the flow-field plate (bipolar plate, which also ensures electric contact with the next cell), gaskets to ensure tightness to reactants and end plates (Figure 9.4). 

Carbon meets many of these requirements and has been used by fuel cell makers over many years. Nevertheless, the development of low-cost, nonporous, carbon materials continues to be a challenge and the bipolar plate remains one of the most costly components in a PEMFC system. 

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... 

Cooper, J.S. Design analysis of PEMFC bipolar plates considering stack manufacturing and environment impact. J. Power Sources 2004, 129 (2), 152-169. 

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

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. 

The PEMFC is constructed in layers of bipolar plates, electrodes, and... 

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. 

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... 

Makkus etal. [46, 47] used 316L SS as a basis for their alloy development. Although 316L SS provided a reasonable stable stack output, they claimed that it is not an optimum choice for PEMFC bipolar plates owing to the interfacial... 

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