Proton Exchange Membrane PEM Fuel Cells

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). 

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. 

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. 

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. 

PEM Proton-exchange-membrane fuel cell (Polymer-electrolyte-membrane fuel cell) Proton- conducting polymer membrane (e.g., Nafion ) H+ (proton) 50-80 mW (Laptop) 50 kW (Ballard) modular up to 200 kW 25-=45% Immediate Road vehicles, stationary electricity generation, heat and electricity co-generation, submarines, space travel... 

Fenton, J. M., Mittal, V. O. and Kunz, H. R. 2007. Durability and degradation of Nation and Nation composite membranes in working PEM fuel cells. In Advances in materials for proton exchange membrane fuel cell systems, Pacific Grove, CA, Feb. 18-21. 

Proton exchange membrane fuel cells (PEMFCs) work with a polymer electrolyte in the form of a thin, permeable sheet. The PEMFCs, otherwise known as polymer electrolyte fuel cells (PEFC), are of particular importance for the use in mobile and small/medium-sized stationary applications (Pehnt, 2001). The PEM fuel cells are considered to be the most promising fuel cell for power generation (Kazim, 2000). 

P P Po PCHE PCR PCS PDF PDMS Pe PEM PEMFC PET pH Power output Pressure Pressure drop of one SAR step Printed circuit heat-exchanger Printed circuit reactor Process control system Probability density function Poly-dimethylsiloxane Peclet-number Proton exchange membrane Proton exchange membrane fuel cell Poly-ethylene terephthalate Potentia Hydrogenii (measure for acid and base strength)... 

PEFC - Polymer Electrolyte Fuel Cell or PEM-FC - Proton Exchange Membrane Fuel Cell... 

Nallathambi V, Lee JW, Kumaraguru SP, Wu G, Popov BN (2008) Development of high performance carbon composite catalysts for oxygen reduction in PEM proton exchange membrane fuel cells. J Power Sotuces 183 34-42... 

---