Membrane fuel cell, components PEMFC

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. 

Proton Exchange Membrane Fuel Cells (PEMFCs) are being considered as a potential alternative energy conversion device for mobile power applications. Since the electrolyte of a PEM fuel cell can function at low temperatures (typically at 80 °C), PEMFCs are unique from the other commercially viable types of fuel cells. Moreover, the electrolyte membrane and other cell components can be manufactured very thin, allowing for high power production to be achieved within a small volume of space. Thus, the combination of small size and fast start-up makes PEMFCs an excellent candidate for use in mobile power applications, such as laptop computers, cell phones, and automobiles. 

Because of its lower temperature and special polymer electrolyte membrane, the proton exchange membrane fuel cell (PEMFC) is well-suited for transportation, portable, and micro fuel cell applications. But the performance of these fuel cells critically depends on the materials used for the various cell components. Durability, water management, and reducing catalyst poisoning are important factors when selecting PEMFC materials. 

The internal resistance of a fuel cell includes the electric contact resistance among the fuel cell components, and the proton resistance of the proton-conducting membrane. In PEMFCs, the proton resistance of the polymer electrolyte membrane contributes the most to the total ohmic resistance. 

It has been demonstrated that EIS can serve as a standard analytical diagnostic tool in the evaluation and characterization of fuel cells. Scientists and engineers have now realized that the entire frequency response spectrum can provide useful data on non-Faradaic mechanisms, water management, ohmic losses, and the ionic conductivity of proton exchange membranes. EIS can help to identify contributors to PEMFC performance. It also provides useful information for fuel cell optimization and for down-selection of the most appropriate operating conditions. In addition, EIS can assist in identifying problems or predicting the likelihood of failure within fuel cell components. 

The 3,4,5,6,7,8-hexahydro-l,2-oxathiocin 2,2-dioxide is the key component for the synthesis of a polymer used for proton exchange membrane fuel cells (PEMFCs). Membranes made with this polymer are pliant, do not expand much during wet conditions, and are chemically, hydrolytically, and thermally stable <2006USP0135702>. 

An electrolyte is an essential component within fuel cells, used to facilitate the selective migration of ions between the electrodes. Fuel cells are typically classified according to the electrolytes used alkaline fuel cell (AFC), polymer electrolyte (or proton exchange membrane) fuel cell (PEMFC), phosphoric acid fuel cell (PAFC),... 

In last few years there has been considerable amount of activity in using ink-jet technology for printing different components of a fuel cell particularly those for polymer electrolyte membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC). The various components reported to have been printed using ink-jet are as follows ... 

From the basic components to parts, modules, and the final system, many types of evaluations are involv in a proton exchange membrane fuel cell (PEMFC). Some evaluations can be done in minutes or hours, while some other evaluations may take weeks, months, or even years. This chapter briefly describes the major evaluations. 

Fuel cells [i.e., polymer electrolyte membrane fuel cells (PEMFCs)] in vehicle drivetrains returned to the agenda in the early 1990s with the Mercedes-Benz NECAR van in 1994. A substantial number of concepts have been developed since then, and several manufacturers envisage market introduction within a few years. The following section describes in detail concepts and components of fuel cell (hybrid) electric vehicles. 

Calculating the structural properties of the component from its chemical composition (e.g., for the case of polymer electrolyte membrane fuel cell (PEMFC) electrodes, by using coarse-grain molecular dynamics (CGMD)) (Fig. 10)... 

PEMFCs are very clean systems and act as filters for impurities introduced from ambient air, fuel used, and even degradation products from the cell materials. Both the membrane and the catalyst are susceptible to cmitamination and poisoning. Electrode degradation of PEMFCs can occur as a result of various impurities found in the fuel feed, air stream, as well as corrosimi by-products from fuel cell components such as the bipolar plate, catalysts, or membrane. 

Direct hydrogen-fuel-cell-powered vehicles have reached a level of development where the major automotive companies have publicly announced that initiation of commercialization is imminent around 2015. The targets of performance, durability, and cost agreed upon by various organizations, including the US DOE, appear to be achievable in the specified time frame. Well-delineated pathways and strategies have been established to address the barriers of cost and durability of PEMFC stacks and achieve the automotive targets. The principal directions for reduction of cost and enhancement of durability of key fuel cell components, i.e., electrocatalysts, membranes, and bipolar plates are briefly summarized in this section. 

Future work in contamination mitigation in PEMFCs should include improving gas stream filtering methodologies as well as developing more contamination tolerant fuel cell components, such as the catalyst, catalyst layers, and membranes. 

Abstract One of the most critical fuel cell components is the catalyst layer, where electrochemical reduction and oxidation of the reactants and fuels take place kinetics and transport properties influence cell jjerformance. Fundamentals of fuel cell catalysis are explain, concurrent reaction pathways of the methanol oxidation reaction are discussed and a variety of catalysts for applications in low temperature fuel cells is described. The chapter highlights the most common polymer electrolyte membrane fuel cell (PEMFC) anode and cathode catalysts, core shell particles, de-alloyed structures and platinum-free materials, reducing platinum content while ensuring electrochemical activity, concluding with a description of different catalyst supports. The role of direct methanol fuel cell (DMFC) bi-fimctional catalysts is explained and optimization strategies towards a reduction of the overall platinum content are presented. 

Abstract Most of the transport processes of a fuel cell take place in the gas diffusion media and flow fields. The task of the flow fleld is to uniformly distribute the reactant gases across the electrochemically active area and at the same time ensure an adequate removal of the reactant products, which is water on the cathode side in both polymer electrolyte membrane fuel cells (PEMFC) and direct methanol fuel cells (DMFC). Gas diffusion media are required to supply the reactant under the land areas of the flow fleld at the same time, the gas diffusion media has to ensure a good thermal as well as water management to avoid any non-optimum conditions. Characterization tools for gas diffusion media are presented, flow fleld types and design criteria are discussed and the effect of both components on the performance of a fuel cell are highlighted. System aspects for different fuels (hydrogen, vapor-fed DMFCS, liquid fed DMFCs) are compiled and the different loss contributions and factors determining the performance of a fuel cell system are shown. 

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