Fuel cells PEMs

In the case of 50 kW power, the rate of hydrogen supply needed (LH) is around 1.69 X 103 (mol/h) at the energy-conversion-efficiency level of 45% for the proton exchange membrane fuel cell (PEM-FC) [38]. 

DMFCs and direct ethanol fuel cells (DEFCs) are based on the proton exchange membrane fuel cell (PEM FC), where hydrogen is replaced by the alcohol, so that both the principles of the PEMFC and the direct alcohol fuel cell (DAFC), in which the alcohol reacts directly at the fuel cell anode without any reforming process, will be discussed in this chapter. Then, because of the low operating temperatures of these fuel cells working in an acidic environment (due to the protonic membrane), the activation of the alcohol oxidation by convenient catalysts (usually containing platinum) is still a severe problem, which will be discussed in the context of electrocatalysis. One way to overcome this problem is to use an alkaline membrane (conducting, e.g., by the hydroxyl anion, OH ), in which medium the kinetics of the electrochemical reactions involved are faster than in an acidic medium, and then to develop the solid alkaline membrane fuel cell (SAMFC). 

Sart Tilman Project Establishment of Ballard stationary fuel cell, PEM of 220 kW. 

With regard to low temperature fuel cells (PEM), efforts must be guided to materials development (catalysts, electrodes, electrolytes, plates, seals, etc), fuel cells components development and its manufacturing methods, fuel cells prototypes development, systems based in fuel cells for transport, stationary and portable applications, and fuel processors. 

Fuel cells can be broadly classified into two types high temperature fuel cells such as molten carbonate fuel cells (MCFCs) and solid oxide polymer fuel cells (SOFCs), which operate at temperatures above 923 K and low temperature fuel cells such as proton exchange membrane fuel cells (PEMs), alkaline fuel cells (AFCs) and phosphoric acid fuel cells (PAFCs), which operate at temperatures lower than 523 K. Because of their higher operating temperatures, MCFCs and SOFCs have a high tolerance for commonly encountered impurities such as CO and CO2 (CO c)- However, the high temperatures also impose problems in their maintenance and operation and thus, increase the difficulty in their effective utilization in vehicular and small-scale applications. Hence, a major part of the research has been directed towards low temperature fuel cells. The low temperature fuel cells unfortunately, have a very low tolerance for impurities such as CO , PAFCs can tolerate up to 2% CO, PEMs only a few ppm, whereas the AFCs have a stringent (ppm level) CO2 tolerance. 

Alkaline fuel cells (AFC) — The first practical -+fuel cell (FC) was introduced by -> Bacon [i]. This was an alkaline fuel cell using a nickel anode, a nickel oxide cathode, and an alkaline aqueous electrolyte solution. The alkaline fuel cell (AFC) is classified among the low-temperature FCs. As such, it is advantageous over the protonic fuel cells, namely the -> polymer-electrolyte-membrane fuel cells (PEM) and the - phosphoric acid fuel cells, which require a large amount of platinum, making them too expensive. The fast oxygen reduction kinetics and the non-platinum cathode catalyst make the alkaline cell attractive. 

This chapter has presented a brief history of fuel cell evolution, the electrochemical fundamentals of PEM fuel cells, PEM fuel cell concepts and terminology, as well as performance analysis. Its main purpose has been to provide readers with some introductory and background information for a fundamental understanding of fuel cell AC impedance, to facilitate their journey through the next several chapters. 

In order to overcome the problem of the short distance range, researches on proton membrane fuel cell (PEM) technology for EV application are underway in many places. 

On the other hand, the largest disadvantage is that the protonic resistance of the Sr-Ce-Yb oxide was comparatively larger than that of a polymer-electrolyte-membrane fuel cell (PEM-FC) and was comparable with 0 ion conductivity of an yttria-stabilised zirconia (YSZ). Consequently, as seen in Figs. 4 and 5, the current density through the Sr-Ce-Yb oxide fuel cell was order of niA/cni and was much smaller than that of PEM-FC. This is because a thin ceramic is very difficult to manufacture. The protonic conductivity of the Sr-Ce-Yb oxide itself was around one-tenth smaller than that of PEM. Moreover, the conductivity was order of 10 " S/cm when a CH4 and HjO mixture was supplied directly to the cell without external reformer. The overall conductivity became around 10 -fold less than that of PEM, because the rate-controlling step was in the steam-reforming reaction. 

ITFC = intermediate-temperature fuel cells PEM-FC = polymer electrolyte membrane fuel cells. 

Develop neutron-imaging methods to accurately measure water gradients across a fuel cell PEM membrane. 

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... 

Ashcraft JN, Avni A, Argun AA, Hammond PT (2010) Structure-property studies of highly conductive layer-by-layer assembled membranes for fuel cell PEM applications. J Mater Chem 20 6250-6257... 

Note-. < FC in all types denotes fuel cell. PEM proton exchange membrane DM direct methanol A alkaline PA phosphoric acid MC molten carbonate SO solid oxide. 

Electrochemical impedance spectroscopy is usually presented in electrochemistry handbooks [12-22], although such presentations are usually quite brief. There are few books on impedance in English [3, 23-26], one in Russian [27], one on differential impedance analysis [28], and many chapters on specific topics [29-72]. The first book [23] on the topic was edited by Macdonald and centered on solid materials the second edition [24] by Macdonald and Barsoukov was enlarged by including other applications. Recently, three new books, by Orazem and Tribollet [3], by Yuan et al. [26] on proton exchange membrane fuel cells (PEM EC), and by Lvovich [25], have been published, while that by Stoynov et al. [27] was never translated into English. A third edition of the book by Macdonald and Barsoukov is in preparation. However, not all aspects of EIS are presented, and these books are not complete in the presentation of their applications. Plenty of review articles on different aspects of impedance and its applications have been published however, they are very specific and can usually be used only by readers who aheady know the basics of this technique. A Scopus search for electrochemical impedance spectroscopy to the end of 2012 comes up with 18,000 papers, most of them since 1996. 

Polymer electrolyte membrane fuel cells (PEM-FCs) have been recognized as a promising alternative power-source for various applications due to their zero... 

Kramm UI, Bogdanoff P, Fiechter S (2013) Non-noble metal catalysts for the oxygen reduction in polymer electrolyte membrane fuel cells (PEM-FC). In Encyclopedia of sustainable science and technology. Springer, New York, pp. 8265-8307... 

Polymer Electrolyte Membrane Fuel Cells (PEM-FC) and Non-noble Metal Catalysts for Oxygen Reduction... 

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