Fuel cell device

Use of Isotopic Effects in the Determination of Electro-Organic Reaction Mechanisms. Much work has been carried out on the mechanism by which hydrocarbons can be clectrochemically oxidized. Were that easy, it might be possible to use available oil in electrochemical devices (fuel cells) to convert chemical to electrical energy 2—3 times more efficiently than do heat engines (Chapter 13). 

The direct conversion of the energy of chemical reactions to electricity in fuel cells (Chapter 13) rather than in heat engines will double the energy available and provide clean and relatively simple devices fuel cells contain no moving parts. 

The main problem in the development of an efficient electrochemical energy conversion device (fuel cell) is in the sluggish ORR kinetics even on the most catalytically active electrode materials, for example, on... 

A.H., Molter, T.M., and Smith, W.F. (1999) Reversible (unitized) PEM fuel cell devices. Fuel Cell Bull., 11, 6-11. 

A variety of practical applications of perovskite systems ABO3 (the piezoelectrical and electro-optical devices, fuel cells, microelectrodes) have stimulated experimental and theoretical investigations of their surfaces. 

CPs, polyaniline (PANI), polythiophene (PTH), polypyrrole (PPy) have been found to be suitable electrode materials similar to other energy storage devices (fuel cells, photoelectrochemical, and batteries) [19-21], Table 1 shows the theoretical and experimental capacitance data of few selected conducting polymers. With the nano-engineered techniques, 3-D stmctures of CPs gain many interests toward... 

A. V. Virkar, K-Z. Fung and C. W. Tanner, Electrode Design for Solid State Devices, Fuel Cells and Sensors, U. S. Patent No. 5,543,239, August 6, 1996. 

The main technological drivers are listed in the Table 1. To compete with existing energy conversion devices, fuel cell systems must have high performance (both power density and efficiency), durability, low cost and, to fit in most niches, fuel flexibility. Whilst there are significant engineering challenges to achieve all these points, they aU require careful selection of the component materials in the cells. 

In the finely divided state platinum is an excellent catalyst, having long been used in the contact process for producing sulfuric acid. It is also used as a catalyst in cracking petroleum products. Much interest exists in using platinum as a catalyst in fuel cells and in antipollution devices for automobiles. 

Sodium terbium borate is used in solid-state devices. The oxide has potential application as an activator for green phosphors used in color TV tubes. It can be used with Zr02 as a crystal stabilizer of fuel cells which operate at elevated temperature. Few other uses have been found. 

Hydrogen use as a fuel in fuel cell appHcations is expected to increase. Fuel cells (qv) are devices which convert the chemical energy of a fuel and oxidant directiy into d-c electrical energy on a continuous basis, potentially approaching 100% efficiency. Large-scale (11 MW) phosphoric acid fuel cells have been commercially available since 1985 (276). Molten carbonate fuel cells (MCFCs) ate expected to be commercially available in the mid-1990s (277). 

Fuel Cell Catalysts. Euel cells (qv) are electrochemical devices that convert the chemical energy of a fuel direcdy into electrical and thermal energy. The fuel cell, an environmentally clean method of power generation (qv), is more efficient than most other energy conversion systems. The main by-product is pure water. 

For a large number of applications involving ceramic materials, electrical conduction behavior is dorninant. In certain oxides, borides (see Boron compounds), nitrides (qv), and carbides (qv), metallic or fast ionic conduction may occur, making these materials useful in thick-film pastes, in fuel cell apphcations (see Fuel cells), or as electrodes for use over a wide temperature range. Superconductivity is also found in special ceramic oxides, and these materials are undergoing intensive research. Other classes of ceramic materials may behave as semiconductors (qv). These materials are used in many specialized apphcations including resistance heating elements and in devices such as rectifiers, photocells, varistors, and thermistors. 

The industrial economy depends heavily on electrochemical processes. Electrochemical systems have inherent advantages such as ambient temperature operation, easily controlled reaction rates, and minimal environmental impact (qv). Electrosynthesis is used in a number of commercial processes. Batteries and fuel cells, used for the interconversion and storage of energy, are not limited by the Carnot efficiency of thermal devices. Corrosion, another electrochemical process, is estimated to cost hundreds of millions of dollars aimuaUy in the United States alone (see Corrosion and CORROSION control). Electrochemical systems can be described using the fundamental principles of thermodynamics, kinetics, and transport phenomena. 

A fuel cell is simply a device with two electrodes and an electrolyte for extracting power from the oxidation of a fuel without combustion, converting the power released directly into electricity. The fuel is usually hydrogen. The principle of a fuel cell was first demonstrated by Sir William Grove in London in 1839 with sulphuric acid and platinum gauze as an electrocatalyst, and thereafter there were very occasional attempts to develop the principle, not all of which were based on sound scientific principles , as one commentator put it. 

A fuel cell is equivalent to a generator it converts a fuel s chemical energy directly into electricity. The main difference between these energy conversion devices is that the fuel cell acccomplishes this directly, "without the two additional intermediate steps, heat release and mechanical motion. 

Fuel cell is an ambiguous term because, although the conversion occurs inside a fuel cell, these cells need to be stacked together, in a fuel cell stack, to produce useful output. In addition, various ancillai y devices are required to operate the stack properly, and these components make up the rest of the fuel cell system. In this article, fuel cell will be taken to mean fuel cell system (i.e., a complete standalone device that generates net power). 

The tape-casting method makes possible the fabrication of films in the region of several hundred micrometers thick. The mechanical strength allows the use of such a solid electrolyte as the structural element for devices such as the high-temperature solid oxide fuel cell in which zirconia-based solid electrolytes are employed both as electrolyte and as mechanical separator of the electrodes. 

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