Polymer electrolyte membranes principle

The principle of the fuel cell was first demonstrated by Grove in 1839 [W. R. Grove, Phil. Mag. 14 (1839) 137]. Today, different schemes exist for utilizing hydrogen in electrochemical cells. We explain the two most important, namely the Polymer Electrolyte Membrane Fuel Cell (PEMFC) and the Solid Oxide Fuel Cell (SOFC). 

Figure 8.31. Principle of a Polymer Electrolyte Membrane (PEM) fuel cell. A Nation membrane sandwiched between electrodes separates hydrogen and oxygen. Hydrogen is oxidized into protons and electrons at the anode on the left. Electrons flow through the outer circuit, while protons diffuse through the...

Stephen J. Paddison received a B.Sc.(Hon.) in Chemical Physics and a Ph.D. (1996) in Physical/Theoretical Chemistry from the University of Calgary, Canada. He was, subsequently, a postdoctoral fellow and staff member in the Materials Science Division at Los Alamos National Laboratory, where he conducted both experimental and theoretical investigations of sulfonic acid polymer electrolyte membranes. This work was continued while he was part of Motorola s Computational Materials Group in Los Alamos. He is currently an Assistant Professor in the Chemistry and Materials Science Departments at the University of Alabama in Huntsville, AL. Research interests continue to be in the development and application of first-principles and statistical mechanical methods in understanding the molecular mechanisms of proton transport in fuel-cell materials. 

Basic Principle of Operation of Polymer Electrolyte Membrane Fuel Cells.760... 

The fuel solution is fed into the anode side channel. Methanol reacts at the anode and releases electrons, protons, and carbon dioxide. At the cathode, molecnlar oxygen reacts with proton being transported throngh the PEM (Polymer Electrolyte Membrane) from the anode and prodnces water. The electrons travel throngh the external circnit to the cathode. Power generation is performed by the above oxidation-rednction reaction principles. In order to realize micro-mini power sonrces, large nnmbers of DMFC shonld be integrated serially on a substrate. The structure of the proposed DMFC is suitable for this application. 

Fig. 1 Operation principle of the various types of fuel cells PEMFC polymer electrolyte membrane fuel cell, AFC alkatine fuel cell, PAFC phosphoric add fuel cell, MCFC molten carbonate fuel cell, SOFC sohd oxide fuel cell...

Looking back, the only unequivocal membrane improvement, in spite of all these efforts, has been the reduction of thickness from 200 jjim in 1995 to <50 (jun in 2005. In terms of chemical or morphological modifications at the microstructural level, no definite recommendations could be discerned so far. The focus of the works reviewed herein has been exploring the fundamental relations between micromorphology and transport from micro- to macroscales for prototypical polymer electrolyte membranes and the understanding of their major principles of operation. 

At present, most of the work toward building methanol fuel cells relies on technical and design principles, developed previously for polymer electrolyte membrane fuel cells. In both kinds of fuel cells, it is common to use platinum-ruthenium catalysts at the anode and a catalyst of pure platinum at the cathode. In the direct methanol fuel cells, the membrane commonly used is of the same type as in the hydrogen-oxygen fuel cells. The basic differences between these versions are discussed in Section 19.7. 

Polymer Electrolyte membrane Fuel Cells (PEFC) are used to power uninterruptible power supplies, combined heat and power generation systems, vehicles for materials handling as well as electric vehicles, busses and light duty road vehicles. This contribution gives a short introduction into the working principles of PEFC as well as the materials and components used. 

Nature of proton dynamics in a polymer electrolyte membrane, Nation a first-principles molecular dynamics study. Phys. Chem. Chem. Phys., 11, 3892-3899. 

We begin with the discussion of cell thermodynamics and electrochemistry basics (Chapter 1). This chapter may serve as an introduction to the field and we hope it would be useful for the general reader interested in the problem. Chapter 2 is devoted to basic principles of structure and operation of the polymer electrolyte membrane. Chapter 3 discusses micro- and mesoscale phenomena in catalyst layers. Chapter 4 presents recent results in performance modeling of catalyst layers, and in Chapter 5 the reader will find several applications of the modeling approaches developed in the preceding chapters. 

The polymer electrolyte membrane (PEM) is the heart of the polymer electrolyte fuel cell (PEFC). It separates the partial redox reactions at anode and cathode and, thereby, enables the fuel cell principle. 

Fuel cells can be classified into phosphoric acid fuel cells, molten carbonate fuel cells, solid oxide full cells, polymer electrolyte membrane fuel cells, and alkaline full cells according to the type of electrolyte used (150). All these fuel cells operate on the same principle, but the t) e of fuel used, operating speed, the catalyst used and the electrolyte used are different. In particular, pol5mier electrolyte membrane fuel cells can be used in small-sized stationary power generation equipment or transportation systems due to their high reaction speed, low operating temperature, high output density, rapid startup, and variation in the requested output. 

Since the type of electrolyte material dictates operating principles and characteristics of a fuel cell, a fuel cell is generally named after the type of electrolyte used. For example, an alkaline fuel cell (AFC) uses an alkaline solution such as potassium hydroxide (KOH) in water, an acid fuel cell such as phosphoric acid fuel cell (PAFC) uses phosphoric acid as electrolyte, a solid polymer electrolyte membrane fuel cell (PEMFC) or proton exchange membrane fuel cell uses proton-conducting solid polymer electrolyte membrane, a molten carbonate fuel cell (MCFC) uses molten lithium or potassium carbonate as electrolyte, and a solid oxide ion-conducting fuel cell (SOFC) uses ceramic electrolyte membrane. 

The content of the book has three main themes basic principles, design, and analysis. The theme of basic principles provides the necessary background information on the fuel cells, including the fundamental principles such as the electrochemistry, thermod5mamics, and kinetics of fuel cell reactions as well as mass and heat transfer in fuel cells. It also provides an overview of the key principles of the most important types of fuel cells and their related systems and applications. This includes polymer electrolyte membrane fuel... 

Direct methanol fuel cells are a class of polymer electrolyte membrane (PEM) fuel cells that typically employ a cation exchange membrane to separate the anode and cathode compartments. To illustrate the basic principles of DMFC operations, we shall take a typical, liquid-feed cell with a cation exchange membrane (alkaline exchange membranes are an alternative, and these are discussed later in this chapter). This is depicted in Figure 5.1. 

The purpose of the present review is to summarize the current status of fundamental models for fuel cell engineering and indicate where this burgeoning field is heading. By choice, this review is limited to hydrogen/air polymer electrolyte fuel cells (PEFCs), direct methanol fuel cells (DMFCs), and solid oxide fuel cells (SOFCs). Also, the review does not include microscopic, first-principle modeling of fuel cell materials, such as proton conducting membranes and catalyst surfaces. For good overviews of the latter fields, the reader can turn to Kreuer, Paddison, and Koper, for example. 

The description given here is a basic outline of the principles of the solid polymer electrolyte fuel cell used in the first Gemini space flights with nonfluorinated membranes (Fig. 13.23). Because the cell is slated for development as part of the electrochemical engine in cars, stages in its modern development are described in another section. 

Current research is centred on making compact cells of high efficiency. They are described in terms of the electrolyte that is used. The principle types are alkali fuel cells, described above, with aqueous KOH as electrolyte, MCFCs (molten carbonate fuel cells), with a molten alkali metal or alkaline earth carbonate electrolyte, PAFCs (phosphoric acid fuel cells), PEMs (proton exchange membranes), using a solid polymer electrolyte that conducts ions, and SOFCs, (solid oxide fuel cells), with solid electrolytes that allow oxide ion, 0 , transport The... 

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