Membrane electrode assembly components

Kraemer, S. V., Lindbergh, G., Lafitte, B., Puchner, M., andJannasch, P. Substitution of Nafion with sulfonated polysulfone in membrane-electrode assembly components for 60-120°C PEMFC operation. Journal of the Electrochemical Society 2008 155 B1001-B1007. 

The three components of the fuel cell, anode, cathode, and electrolyte form a membrane-electrolyte assembly, as, by analogy with polymer electrolyte fuel cells, one may regard the thin layer of solid electrolyte as a membrane. Any one of the three membrane-electrode assembly components can be selected as the entire fuel cell s support and made relatively thick (up to 2 mm) in order to provide mechanical stability. The other two components are then applied to this support in a different way as thin layers (tenths of a millimeter). Accordingly, one has anode-supported, electrolyte-supported, and cathode-supported fuel cells. Sometimes though an independent metal or ceramic substrate is used to which, then, the three functional layers are applied. 

Fig. 7 Membrane electrode assembly Components and physical processes occurring at the interfaces.

Sol-gel techniques have been successfidly applied to form fuel cell components with enhanced microstructures for high-temperature fuel cells. The apphcations were recently extended to synthesis of hybrid electrolyte for PEMFC. Although die results look promising, the sol-gel processing needs further development to deposit micro-structured materials in a selective area such as the triple-phase boundary of a fuel cell. That is, in the case of PEMFC, the sol-gel techniques need to be expanded to form membrane-electrode-assembly with improved microstructures in addition to the synthesis of hybrid membranes to get higher fuel cell performance. 

These selection and evaluation criteria were applied systematically to four technological fields, three of which contribute to new energy-efficient solutions. Passive houses, for example, with their major components of insulation solutions, window systems, ventilation and control techniques are close to market diffusion within the next ten years. Fuel cells for mobile uses in vehicles, however, are still a long way from market introduction, for instance, because of unresolved problems regarding the deactivation of the membrane electrode assembly (MEA) and the need for cost reductions by about one order of magnitude. Other types of fuel cells for stationary uses may be closer to market introduction, owing to less severe technical bottlenecks and better economic competitiveness. 

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.). 

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). 

The membrane electrode assembly (MEA), which consists of three components (two gas diffusion electrodes with a proton exchange membrane in between), is the most important component of the PEMFC. The MEA exerts the largest influence on the performance of a fuel cell, and the properties of each of its parts in turn play significant roles in that performance. Although all the components in the MEA are important, the gas diffusion electrode attracts more attention because of its complexity and functions. In AC impedance spectra, the proton exchange membrane usually exhibits resistance characteristics the features of these spectra reflect the properties of the gas diffusion electrode. In order to better understand the behaviour of a gas diffusion electrode, we introduce the thin-film/flooded agglomerate model, which has been successfully applied by many researchers to... 

The heart of a fuel cell is the membrane electrode assembly (MEA). In the simplest form, the electrode component of the MEA would consist of a thin film containing a highly dispersed nanoparticle platinum catalyst. This catalyst layer is in good contact with the ionomeric membrane, which serves as the reactant gas separator and electrolyte in this cell. The membrane is about 25-100 p,m thick. The MEA then consists of an ionomeric membrane with thin catalyst layers bonded on each side. Porous and electrically conducting carbon paper/cloth current collectors act as gas distributors (Figure 27.1). Since ohmic losses occur within the ionomeric membrane, it is important to maximize the proton conductivity of the membrane, without sacrificing the mechanical and chemical stability. 

Develop a solid superacid-Nafion composite membrane electrode assembly (MEA) with the following components ... 

Specify membrane electrode assembly (MEA) component parameters and conduct final pilot scale runs to generate process statistics. 

To understand the modifications made to polysaccharides in PEMs applications, a cursory knowledge of fuel cells is necessary. A fuel cell is an electrochemical cell that converts chemical fuel into electrical energy. Figure 3.4 shows a simplified view of a proton conductive fuel cell. The main components in a PEM fuel cell are catalyst layers, gas diffusion layers and the PEM itself. These three components comprise the membrane electrode assembly. The catalyst... 

Fig. 3 Components of the polymer electrolyte fuel cell (PEFC) membrane electrode assembly (MEA) on the left, including separator plates and gasket. A schematic of a PEFC stack is shown on the right, comprising a number of single cells in series...

In the PEFC, the membrane, together with the electrodes, forms the basic electrochemical unit, the membrane electrode assembly (MEA). The first and foremost function of the electrolyte membrane is the transport of protons from anode to cathode. On one hand, the electrodes host the electrochemical reactions within the catalyst layer and provide electronic conductivity, and, on the other hand, they provide pathways for reactant supply to the catalyst and removal of products from the catalyst. The components of the MEA need to be chemically stable for several thousands of hours in the fuel ceU under the prevailing operating and transient conditions. PEFC electrodes are wet-proofed fibrous carbon sheet materials of a few 100 ttm thickness. The functionality of the proton exchange membrane (PEM) extends to requirements of mechanical stability to also ensure effective separation of anode and... 

The development of membranes for fuel cells is a highly complex task. The primary functionalities, (i) transport of protons and (ii) separation of reactants and electrons, have to be provided and sustained for the required operating time. Optimization of the composition and structure of the material to maximize conductivity and mechanical robustness involves careful balancing of synthesis and process parameters. The ultimate membrane qualification test is the fuel cell experiment. It is evident that the membrane is not a stand-alone component, but is combined with the electrodes in the membrane electrode assembly (MEA). Interfacial properties, influence on anode and cathode electrocatalysis, and water management are the key aspects to be considered and optimized in this ensemble. 

The Membrane Electrode Assembly (MEA) is the core component of a PEFC, in which electric current is generated by anodic oxidation of the fuel which typically is hydrogen or methanol and cathodic reduction of the oxidant which typically is oxygen from the air. The MEA contains all electrochemically relevant interfaces at the anode and the cathode side. The central part of the MEA is formed by the... 

A wide variety of sealing solutions have been reported such as the use of O-rings or die cut flat seals, adhesive bonding of the components, molded, dispensed or screen printed elastomers to the bipolar plate or the membrane electrode assembly, separate sealing frames, bead seals on metallic bipolar plates etc. [6, 75, 76]. 

The main component of a Polymer Electrolyte Membrane Fuel CeU (PEMFQ is the Membrane Electrode Assembly (MEA) [1,2]. The MEA is formed by a polymer membrane flanked by two electrodes. The membrane acts as the ionic conductor between the two electrodes the anode, where the fuel is oxidized, and the cathode, where the oxidant is reduced. The electrodes are formed by a porous material named Gas Diffusion Layer (GDL) with a thin layer of an electrocatalyst denominated the Catalyst Layer (CL), The electrocatalyst, responsible of driving... 

Further, The IPHE Coordination Action for Research on Intermediate and High Temperature Speciahzed Membrane Electrode Assemblies (CARISMA) seeks to network research activities in Europe on high temperature membrane electrode assemblies (MEAs) and their components. Coordination activities are centered on membranes, catalysts, and high temperature MEAs. 

The basic components of the SOFC are the anode, the cathode and the electrolyte, as shown in Fig. 10.1. They are together referred to as the membrane electrode assembly (MEA). Fuel (hydrogen) is supplied to the anode side and air is supplied to the cathode side. At the cathode-electrolyte interface, oxygen molecules accept electrons coming from the external circuit to form oxide ions. The solid electrolyte allows only oxide ions to pass through. At the anode-electrolyte interface, hydrogen molecules present in the fuel react with oxide ions to form steam, and electrons get released. As a result of the potential difference set up between anode and cathode... 

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